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Independent Submission                                    R. Pantos, Ed.Request for Comments: 8216                                   Apple, Inc.Category: Informational                                           W. MayISSN: 2070-1721                                       MLB Advanced Media                                                             August 2017HTTP Live StreamingAbstract   This document describes a protocol for transferring unbounded streams   of multimedia data.  It specifies the data format of the files and   the actions to be taken by the server (sender) and the clients   (receivers) of the streams.  It describes version 7 of this protocol.Status of This Memo   This document is not an Internet Standards Track specification; it is   published for informational purposes.   This is a contribution to the RFC Series, independently of any other   RFC stream.  The RFC Editor has chosen to publish this document at   its discretion and makes no statement about its value for   implementation or deployment.  Documents approved for publication by   the RFC Editor are not a candidate for any level of Internet   Standard; seeSection 2 of RFC 7841.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc8216.Copyright Notice   Copyright (c) 2017 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.   This document may not be modified, and derivative works of it may not   be created, except to format it for publication as an RFC or to   translate it into languages other than English.Pantos & May                  Informational                     [Page 1]

RFC 8216                   HTTP Live Streaming               August 2017Table of Contents1. Introduction to HTTP Live Streaming .............................42. Overview ........................................................43. Media Segments ..................................................63.1. Supported Media Segment Formats ............................63.2. MPEG-2 Transport Streams ...................................73.3. Fragmented MPEG-4 ..........................................73.4. Packed Audio ...............................................83.5. WebVTT .....................................................84. Playlists .......................................................94.1. Definition of a Playlist ..................................104.2. Attribute Lists ...........................................114.3. Playlist Tags .............................................124.3.1. Basic Tags .........................................124.3.1.1. EXTM3U ....................................124.3.1.2. EXT-X-VERSION .............................124.3.2. Media Segment Tags .................................134.3.2.1. EXTINF ....................................134.3.2.2. EXT-X-BYTERANGE ...........................144.3.2.3. EXT-X-DISCONTINUITY .......................144.3.2.4. EXT-X-KEY .................................154.3.2.5. EXT-X-MAP .................................174.3.2.6. EXT-X-PROGRAM-DATE-TIME ...................184.3.2.7. EXT-X-DATERANGE ...........................18                           4.3.2.7.1. Mapping SCTE-35 into                                      EXT-X-DATERANGE ................204.3.3. Media Playlist Tags ................................224.3.3.1. EXT-X-TARGETDURATION ......................224.3.3.2. EXT-X-MEDIA-SEQUENCE ......................224.3.3.3. EXT-X-DISCONTINUITY-SEQUENCE ..............234.3.3.4. EXT-X-ENDLIST .............................234.3.3.5. EXT-X-PLAYLIST-TYPE .......................244.3.3.6. EXT-X-I-FRAMES-ONLY .......................244.3.4. Master Playlist Tags ...............................254.3.4.1. EXT-X-MEDIA ...............................254.3.4.1.1. Rendition Groups ...............284.3.4.2. EXT-X-STREAM-INF ..........................294.3.4.2.1. Alternative Renditions .........324.3.4.3. EXT-X-I-FRAME-STREAM-INF ..................334.3.4.4. EXT-X-SESSION-DATA ........................344.3.4.5. EXT-X-SESSION-KEY .........................354.3.5. Media or Master Playlist Tags ......................354.3.5.1. EXT-X-INDEPENDENT-SEGMENTS ................354.3.5.2. EXT-X-START ...............................36Pantos & May                  Informational                     [Page 2]

RFC 8216                   HTTP Live Streaming               August 20175. Key Files ......................................................375.1. Structure of Key Files ....................................375.2. IV for AES-128 ............................................376. Client/Server Responsibilities .................................376.1. Introduction ..............................................376.2. Server Responsibilities ...................................376.2.1. General Server Responsibilities ....................376.2.2. Live Playlists .....................................406.2.3. Encrypting Media Segments ..........................416.2.4. Providing Variant Streams ..........................426.3. Client Responsibilities ...................................446.3.1. General Client Responsibilities ....................446.3.2. Loading the Media Playlist File ....................446.3.3. Playing the Media Playlist File ....................456.3.4. Reloading the Media Playlist File ..................466.3.5. Determining the Next Segment to Load ...............476.3.6. Decrypting Encrypted Media Segments ................477. Protocol Version Compatibility .................................488. Playlist Examples ..............................................508.1. Simple Media Playlist .....................................508.2. Live Media Playlist Using HTTPS ...........................508.3. Playlist with Encrypted Media Segments ....................518.4. Master Playlist ...........................................518.5. Master Playlist with I-Frames .............................518.6. Master Playlist with Alternative Audio ....................528.7. Master Playlist with Alternative Video ....................528.8. Session Data in a Master Playlist .........................53      8.9. CHARACTERISTICS Attribute Containing Multiple           Characteristics ...........................................548.10. EXT-X-DATERANGE Carrying SCTE-35 Tags ....................549. IANA Considerations ............................................5410. Security Considerations .......................................5511. References ....................................................5611.1. Normative References .....................................5611.2. Informative References ...................................59   Contributors ......................................................60   Authors' Addresses ................................................60Pantos & May                  Informational                     [Page 3]

RFC 8216                   HTTP Live Streaming               August 20171.  Introduction to HTTP Live Streaming   HTTP Live Streaming provides a reliable, cost-effective means of   delivering continuous and long-form video over the Internet.  It   allows a receiver to adapt the bit rate of the media to the current   network conditions in order to maintain uninterrupted playback at the   best possible quality.  It supports interstitial content boundaries.   It provides a flexible framework for media encryption.  It can   efficiently offer multiple renditions of the same content, such as   audio translations.  It offers compatibility with large-scale HTTP   caching infrastructure to support delivery to large audiences.   Since the Internet-Draft was first posted in 2009, HTTP Live   Streaming has been implemented and deployed by a wide array of   content producers, tools vendors, distributors, and device   manufacturers.  In the subsequent eight years, the protocol has been   refined by extensive review and discussion with a variety of media   streaming implementors.   The purpose of this document is to facilitate interoperability   between HTTP Live Streaming implementations by describing the media   transmission protocol.  Using this protocol, a client can receive a   continuous stream of media from a server for concurrent presentation.   This document describes version 7 of the protocol.2.  Overview   A multimedia presentation is specified by a Uniform Resource   Identifier (URI) [RFC3986] to a Playlist.   A Playlist is either a Media Playlist or a Master Playlist.  Both are   UTF-8 text files containing URIs and descriptive tags.   A Media Playlist contains a list of Media Segments, which, when   played sequentially, will play the multimedia presentation.Pantos & May                  Informational                     [Page 4]

RFC 8216                   HTTP Live Streaming               August 2017   Here is an example of a Media Playlist:   #EXTM3U   #EXT-X-TARGETDURATION:10   #EXTINF:9.009,   http://media.example.com/first.ts   #EXTINF:9.009,   http://media.example.com/second.ts   #EXTINF:3.003,   http://media.example.com/third.ts   The first line is the format identifier tag #EXTM3U.  The line   containing #EXT-X-TARGETDURATION says that all Media Segments will be   10 seconds long or less.  Then, three Media Segments are declared.   The first and second are 9.009 seconds long; the third is 3.003   seconds.   To play this Playlist, the client first downloads it and then   downloads and plays each Media Segment declared within it.  The   client reloads the Playlist as described in this document to discover   any added segments.  Data SHOULD be carried over HTTP [RFC7230], but,   in general, a URI can specify any protocol that can reliably transfer   the specified resource on demand.   A more complex presentation can be described by a Master Playlist.  A   Master Playlist provides a set of Variant Streams, each of which   describes a different version of the same content.   A Variant Stream includes a Media Playlist that specifies media   encoded at a particular bit rate, in a particular format, and at a   particular resolution for media containing video.   A Variant Stream can also specify a set of Renditions.  Renditions   are alternate versions of the content, such as audio produced in   different languages or video recorded from different camera angles.   Clients should switch between different Variant Streams to adapt to   network conditions.  Clients should choose Renditions based on user   preferences.   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and   "OPTIONAL" in this document are to be interpreted as described inBCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all   capitals, as shown here.Pantos & May                  Informational                     [Page 5]

RFC 8216                   HTTP Live Streaming               August 20173.  Media Segments   A Media Playlist contains a series of Media Segments that make up the   overall presentation.  A Media Segment is specified by a URI and   optionally a byte range.   The duration of each Media Segment is indicated in the Media Playlist   by its EXTINF tag (Section 4.3.2.1).   Each segment in a Media Playlist has a unique integer Media Sequence   Number.  The Media Sequence Number of the first segment in the Media   Playlist is either 0 or declared in the Playlist (Section 4.3.3.2).   The Media Sequence Number of every other segment is equal to the   Media Sequence Number of the segment that precedes it plus one.   Each Media Segment MUST carry the continuation of the encoded   bitstream from the end of the segment with the previous Media   Sequence Number, where values in a series such as timestamps and   Continuity Counters MUST continue uninterrupted.  The only exceptions   are the first Media Segment ever to appear in a Media Playlist and   Media Segments that are explicitly signaled as discontinuities   (Section 4.3.2.3).  Unmarked media discontinuities can trigger   playback errors.   Any Media Segment that contains video SHOULD include enough   information to initialize a video decoder and decode a continuous set   of frames that includes the final frame in the Segment; network   efficiency is optimized if there is enough information in the Segment   to decode all frames in the Segment.  For example, any Media Segment   containing H.264 video SHOULD contain an Instantaneous Decoding   Refresh (IDR); frames prior to the first IDR will be downloaded but   possibly discarded.3.1.  Supported Media Segment Formats   All Media Segments MUST be in a format described in this section.   Transport of other media file formats is not defined.   Some media formats require a common sequence of bytes to initialize a   parser before a Media Segment can be parsed.  This format-specific   sequence is called the Media Initialization Section.  The Media   Initialization Section can be specified by an EXT-X-MAP tag   (Section 4.3.2.5).  The Media Initialization Section MUST NOT contain   sample data.Pantos & May                  Informational                     [Page 6]

RFC 8216                   HTTP Live Streaming               August 20173.2.  MPEG-2 Transport Streams   MPEG-2 Transport Streams are specified by [ISO_13818].   The Media Initialization Section of an MPEG-2 Transport Stream   Segment is a Program Association Table (PAT) followed by a Program   Map Table (PMT).   Transport Stream Segments MUST contain a single MPEG-2 Program;   playback of Multi-Program Transport Streams is not defined.  Each   Transport Stream Segment MUST contain a PAT and a PMT, or have an   EXT-X-MAP tag (Section 4.3.2.5) applied to it.  The first two   Transport Stream packets in a Segment without an EXT-X-MAP tag SHOULD   be a PAT and a PMT.3.3.  Fragmented MPEG-4   MPEG-4 Fragments are specified by the ISO Base Media File Format   [ISOBMFF].  Unlike regular MPEG-4 files that have a Movie Box   ('moov') that contains sample tables and a Media Data Box ('mdat')   containing the corresponding samples, an MPEG-4 Fragment consists of   a Movie Fragment Box ('moof') containing a subset of the sample table   and a Media Data Box containing those samples.  Use of MPEG-4   Fragments does require a Movie Box for initialization, but that Movie   Box contains only non-sample-specific information such as track and   sample descriptions.   A Fragmented MPEG-4 (fMP4) Segment is a "segment" as defined by   Section 3 of [ISOBMFF], including the constraints on Media Data Boxes   in Section 8.16 of [ISOBMFF].   The Media Initialization Section for an fMP4 Segment is an ISO Base   Media File that can initialize a parser for that Segment.   Broadly speaking, fMP4 Segments and Media Initialization Sections are   [ISOBMFF] files that also satisfy the constraints described in this   section.   The Media Initialization Section for an fMP4 Segment MUST contain a   File Type Box ('ftyp') containing a brand that is compatible with   'iso6' or higher.  The File Type Box MUST be followed by a Movie Box.   The Movie Box MUST contain a Track Box ('trak') for every Track   Fragment Box ('traf') in the fMP4 Segment, with matching track_ID.   Each Track Box SHOULD contain a sample table, but its sample count   MUST be zero.  Movie Header Boxes ('mvhd') and Track Header Boxes   ('tkhd') MUST have durations of zero.  A Movie Extends Box ('mvex')   MUST follow the last Track Box.  Note that a Common Media Application   Format (CMAF) Header [CMAF] meets all these requirements.Pantos & May                  Informational                     [Page 7]

RFC 8216                   HTTP Live Streaming               August 2017   In an fMP4 Segment, every Track Fragment Box MUST contain a Track   Fragment Decode Time Box ('tfdt'). fMP4 Segments MUST use movie-   fragment-relative addressing. fMP4 Segments MUST NOT use external   data references.  Note that a CMAF Segment meets these requirements.   An fMP4 Segment in a Playlist containing the EXT-X-I-FRAMES-ONLY tag   (Section 4.3.3.6) MAY omit the portion of the Media Data Box   following the intra-coded frame (I-frame) sample data.   Each fMP4 Segment in a Media Playlist MUST have an EXT-X-MAP tag   applied to it.3.4.  Packed Audio   A Packed Audio Segment contains encoded audio samples and ID3 tags   that are simply packed together with minimal framing and no per-   sample timestamps.  Supported Packed Audio formats are Advanced Audio   Coding (AAC) with Audio Data Transport Stream (ADTS) framing   [ISO_13818_7], MP3 [ISO_13818_3], AC-3 [AC_3], and Enhanced AC-3   [AC_3].   A Packed Audio Segment has no Media Initialization Section.   Each Packed Audio Segment MUST signal the timestamp of its first   sample with an ID3 Private frame (PRIV) tag [ID3] at the beginning of   the segment.  The ID3 PRIV owner identifier MUST be   "com.apple.streaming.transportStreamTimestamp".  The ID3 payload MUST   be a 33-bit MPEG-2 Program Elementary Stream timestamp expressed as a   big-endian eight-octet number, with the upper 31 bits set to zero.   Clients SHOULD NOT play Packed Audio Segments without this ID3 tag.3.5.  WebVTT   A WebVTT Segment is a section of a WebVTT [WebVTT] file.  WebVTT   Segments carry subtitles.   The Media Initialization Section of a WebVTT Segment is the WebVTT   header.   Each WebVTT Segment MUST contain all subtitle cues that are intended   to be displayed during the period indicated by the segment EXTINF   duration.  The start time offset and end time offset of each cue MUST   indicate the total display time for that cue, even if part of the cue   time range is outside the Segment period.  A WebVTT Segment MAY   contain no cues; this indicates that no subtitles are to be displayed   during that period.Pantos & May                  Informational                     [Page 8]

RFC 8216                   HTTP Live Streaming               August 2017   Each WebVTT Segment MUST either start with a WebVTT header or have an   EXT-X-MAP tag applied to it.   In order to synchronize timestamps between audio/video and subtitles,   an X-TIMESTAMP-MAP metadata header SHOULD be added to each WebVTT   header.  This header maps WebVTT cue timestamps to MPEG-2 (PES)   timestamps in other Renditions of the Variant Stream.  Its format is:   X-TIMESTAMP-MAP=LOCAL:<cue time>,MPEGTS:<MPEG-2 time>   e.g., X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000   The cue timestamp in the LOCAL attribute MAY fall outside the range   of time covered by the segment.   If a WebVTT segment does not have the X-TIMESTAMP-MAP, the client   MUST assume that the WebVTT cue time of 0 maps to an MPEG-2 timestamp   of 0.   When synchronizing WebVTT with PES timestamps, clients SHOULD account   for cases where the 33-bit PES timestamps have wrapped and the WebVTT   cue times have not.4.  Playlists   This section describes the Playlist files used by HTTP Live   Streaming.  In this section, "MUST" and "MUST NOT" specify the rules   for the syntax and structure of legal Playlist files.  Playlists that   violate these rules are invalid; clients MUST fail to parse them.   SeeSection 6.3.2.   The format of the Playlist files is derived from the M3U [M3U]   playlist file format and inherits two tags from that earlier file   format: EXTM3U (Section 4.3.1.1) and EXTINF (Section 4.3.2.1).   In the specification of tag syntax, a string enclosed by <>   identifies a tag parameter; its specific format is described in its   tag definition.  If a parameter is further surrounded by [], it is   optional; otherwise, it is required.   Each Playlist file MUST be identifiable either by the path component   of its URI or by HTTP Content-Type.  In the first case, the path MUST   end with either .m3u8 or .m3u.  In the second, the HTTP Content-Type   MUST be "application/vnd.apple.mpegurl" or "audio/mpegurl".  Clients   SHOULD refuse to parse Playlists that are not so identified.Pantos & May                  Informational                     [Page 9]

RFC 8216                   HTTP Live Streaming               August 20174.1.  Definition of a Playlist   Playlist files MUST be encoded in UTF-8 [RFC3629].  They MUST NOT   contain any Byte Order Mark (BOM); clients SHOULD fail to parse   Playlists that contain a BOM or do not parse as UTF-8.  Playlist   files MUST NOT contain UTF-8 control characters (U+0000 to U+001F and   U+007F to U+009F), with the exceptions of CR (U+000D) and LF   (U+000A).  All character sequences MUST be normalized according to   Unicode normalization form "NFC" [UNICODE].  Note that US-ASCII   [US_ASCII] conforms to these rules.   Lines in a Playlist file are terminated by either a single line feed   character or a carriage return character followed by a line feed   character.  Each line is a URI, is blank, or starts with the   character '#'.  Blank lines are ignored.  Whitespace MUST NOT be   present, except for elements in which it is explicitly specified.   Lines that start with the character '#' are either comments or tags.   Tags begin with #EXT.  They are case sensitive.  All other lines that   begin with '#' are comments and SHOULD be ignored.   A URI line identifies a Media Segment or a Playlist file (seeSection 4.3.4.2).  Each Media Segment is specified by a URI and the   tags that apply to it.   A Playlist is a Media Playlist if all URI lines in the Playlist   identify Media Segments.  A Playlist is a Master Playlist if all URI   lines in the Playlist identify Media Playlists.  A Playlist MUST be   either a Media Playlist or a Master Playlist; all other Playlists are   invalid.   A URI in a Playlist, whether it is a URI line or part of a tag, MAY   be relative.  Any relative URI is considered to be relative to the   URI of the Playlist that contains it.   The duration of a Media Playlist is the sum of the durations of the   Media Segments within it.   The segment bit rate of a Media Segment is the size of the Media   Segment divided by its EXTINF duration (Section 4.3.2.1).  Note that   this includes container overhead but does not include overhead   imposed by the delivery system, such as HTTP, TCP, or IP headers.   The peak segment bit rate of a Media Playlist is the largest bit rate   of any contiguous set of segments whose total duration is between 0.5   and 1.5 times the target duration.  The bit rate of a set is   calculated by dividing the sum of the segment sizes by the sum of the   segment durations.Pantos & May                  Informational                    [Page 10]

RFC 8216                   HTTP Live Streaming               August 2017   The average segment bit rate of a Media Playlist is the sum of the   sizes (in bits) of every Media Segment in the Media Playlist, divided   by the Media Playlist duration.  Note that this includes container   overhead, but not HTTP or other overhead imposed by the delivery   system.4.2.  Attribute Lists   Certain tags have values that are attribute-lists.  An attribute-list   is a comma-separated list of attribute/value pairs with no   whitespace.   An attribute/value pair has the following syntax:   AttributeName=AttributeValue   An AttributeName is an unquoted string containing characters from the   set [A..Z], [0..9] and '-'.  Therefore, AttributeNames contain only   uppercase letters, not lowercase.  There MUST NOT be any whitespace   between the AttributeName and the '=' character, nor between the '='   character and the AttributeValue.   An AttributeValue is one of the following:   o  decimal-integer: an unquoted string of characters from the set      [0..9] expressing an integer in base-10 arithmetic in the range      from 0 to 2^64-1 (18446744073709551615).  A decimal-integer may be      from 1 to 20 characters long.   o  hexadecimal-sequence: an unquoted string of characters from the      set [0..9] and [A..F] that is prefixed with 0x or 0X.  The maximum      length of a hexadecimal-sequence depends on its AttributeNames.   o  decimal-floating-point: an unquoted string of characters from the      set [0..9] and '.' that expresses a non-negative floating-point      number in decimal positional notation.   o  signed-decimal-floating-point: an unquoted string of characters      from the set [0..9], '-', and '.' that expresses a signed      floating-point number in decimal positional notation.   o  quoted-string: a string of characters within a pair of double      quotes (0x22).  The following characters MUST NOT appear in a      quoted-string: line feed (0xA), carriage return (0xD), or double      quote (0x22).  Quoted-string AttributeValues SHOULD be constructed      so that byte-wise comparison is sufficient to test two quoted-      string AttributeValues for equality.  Note that this implies case-      sensitive comparison.Pantos & May                  Informational                    [Page 11]

RFC 8216                   HTTP Live Streaming               August 2017   o  enumerated-string: an unquoted character string from a set that is      explicitly defined by the AttributeName.  An enumerated-string      will never contain double quotes ("), commas (,), or whitespace.   o  decimal-resolution: two decimal-integers separated by the "x"      character.  The first integer is a horizontal pixel dimension      (width); the second is a vertical pixel dimension (height).   The type of the AttributeValue for a given AttributeName is specified   by the attribute definition.   A given AttributeName MUST NOT appear more than once in a given   attribute-list.  Clients SHOULD refuse to parse such Playlists.4.3.  Playlist Tags   Playlist tags specify either global parameters of the Playlist or   information about the Media Segments or Media Playlists that appear   after them.4.3.1.  Basic Tags   These tags are allowed in both Media Playlists and Master Playlists.4.3.1.1.  EXTM3U   The EXTM3U tag indicates that the file is an Extended M3U [M3U]   Playlist file.  It MUST be the first line of every Media Playlist and   every Master Playlist.  Its format is:   #EXTM3U4.3.1.2.  EXT-X-VERSION   The EXT-X-VERSION tag indicates the compatibility version of the   Playlist file, its associated media, and its server.   The EXT-X-VERSION tag applies to the entire Playlist file.  Its   format is:   #EXT-X-VERSION:<n>   where n is an integer indicating the protocol compatibility version   number.Pantos & May                  Informational                    [Page 12]

RFC 8216                   HTTP Live Streaming               August 2017   It MUST appear in all Playlists containing tags or attributes that   are not compatible with protocol version 1 to support   interoperability with older clients.Section 7 specifies the minimum   value of the compatibility version number for any given Playlist   file.   A Playlist file MUST NOT contain more than one EXT-X-VERSION tag.  If   a client encounters a Playlist with multiple EXT-X-VERSION tags, it   MUST fail to parse it.4.3.2.  Media Segment Tags   Each Media Segment is specified by a series of Media Segment tags   followed by a URI.  Some Media Segment tags apply to just the next   segment; others apply to all subsequent segments until another   instance of the same tag.   A Media Segment tag MUST NOT appear in a Master Playlist.  Clients   MUST fail to parse Playlists that contain both Media Segment tags and   Master Playlist tags (Section 4.3.4).4.3.2.1.  EXTINF   The EXTINF tag specifies the duration of a Media Segment.  It applies   only to the next Media Segment.  This tag is REQUIRED for each Media   Segment.  Its format is:   #EXTINF:<duration>,[<title>]   where duration is a decimal-floating-point or decimal-integer number   (as described inSection 4.2) that specifies the duration of the   Media Segment in seconds.  Durations SHOULD be decimal-floating-   point, with enough accuracy to avoid perceptible error when segment   durations are accumulated.  However, if the compatibility version   number is less than 3, durations MUST be integers.  Durations that   are reported as integers SHOULD be rounded to the nearest integer.   The remainder of the line following the comma is an optional human-   readable informative title of the Media Segment expressed as UTF-8   text.Pantos & May                  Informational                    [Page 13]

RFC 8216                   HTTP Live Streaming               August 20174.3.2.2.  EXT-X-BYTERANGE   The EXT-X-BYTERANGE tag indicates that a Media Segment is a sub-range   of the resource identified by its URI.  It applies only to the next   URI line that follows it in the Playlist.  Its format is:   #EXT-X-BYTERANGE:<n>[@<o>]   where n is a decimal-integer indicating the length of the sub-range   in bytes.  If present, o is a decimal-integer indicating the start of   the sub-range, as a byte offset from the beginning of the resource.   If o is not present, the sub-range begins at the next byte following   the sub-range of the previous Media Segment.   If o is not present, a previous Media Segment MUST appear in the   Playlist file and MUST be a sub-range of the same media resource, or   the Media Segment is undefined and the client MUST fail to parse the   Playlist.   A Media Segment without an EXT-X-BYTERANGE tag consists of the entire   resource identified by its URI.   Use of the EXT-X-BYTERANGE tag REQUIRES a compatibility version   number of 4 or greater.4.3.2.3.  EXT-X-DISCONTINUITY   The EXT-X-DISCONTINUITY tag indicates a discontinuity between the   Media Segment that follows it and the one that preceded it.   Its format is:   #EXT-X-DISCONTINUITY   The EXT-X-DISCONTINUITY tag MUST be present if there is a change in   any of the following characteristics:   o  file format   o  number, type, and identifiers of tracks   o  timestamp sequencePantos & May                  Informational                    [Page 14]

RFC 8216                   HTTP Live Streaming               August 2017   The EXT-X-DISCONTINUITY tag SHOULD be present if there is a change in   any of the following characteristics:   o  encoding parameters   o  encoding sequence   See Sections3,6.2.1, and6.3.3 for more information about the EXT-   X-DISCONTINUITY tag.4.3.2.4.  EXT-X-KEY   Media Segments MAY be encrypted.  The EXT-X-KEY tag specifies how to   decrypt them.  It applies to every Media Segment and to every Media   Initialization Section declared by an EXT-X-MAP tag that appears   between it and the next EXT-X-KEY tag in the Playlist file with the   same KEYFORMAT attribute (or the end of the Playlist file).  Two or   more EXT-X-KEY tags with different KEYFORMAT attributes MAY apply to   the same Media Segment if they ultimately produce the same decryption   key.  The format is:   #EXT-X-KEY:<attribute-list>   The following attributes are defined:      METHOD      The value is an enumerated-string that specifies the encryption      method.  This attribute is REQUIRED.      The methods defined are: NONE, AES-128, and SAMPLE-AES.      An encryption method of NONE means that Media Segments are not      encrypted.  If the encryption method is NONE, other attributes      MUST NOT be present.      An encryption method of AES-128 signals that Media Segments are      completely encrypted using the Advanced Encryption Standard (AES)      [AES_128] with a 128-bit key, Cipher Block Chaining (CBC), and      Public-Key Cryptography Standards #7 (PKCS7) padding [RFC5652].      CBC is restarted on each segment boundary, using either the      Initialization Vector (IV) attribute value or the Media Sequence      Number as the IV; seeSection 5.2.      An encryption method of SAMPLE-AES means that the Media Segments      contain media samples, such as audio or video, that are encrypted      using the Advanced Encryption Standard [AES_128].  How these media      streams are encrypted and encapsulated in a segment depends on thePantos & May                  Informational                    [Page 15]

RFC 8216                   HTTP Live Streaming               August 2017      media encoding and the media format of the segment.  fMP4 Media      Segments are encrypted using the 'cbcs' scheme of Common      Encryption [COMMON_ENC].  Encryption of other Media Segment      formats containing H.264 [H_264], AAC [ISO_14496], AC-3 [AC_3],      and Enhanced AC-3 [AC_3] media streams is described in the HTTP      Live Streaming (HLS) Sample Encryption specification [SampleEnc].      The IV attribute MAY be present; seeSection 5.2.      URI      The value is a quoted-string containing a URI that specifies how      to obtain the key.  This attribute is REQUIRED unless the METHOD      is NONE.      IV      The value is a hexadecimal-sequence that specifies a 128-bit      unsigned integer Initialization Vector to be used with the key.      Use of the IV attribute REQUIRES a compatibility version number of      2 or greater.  SeeSection 5.2 for when the IV attribute is used.      KEYFORMAT      The value is a quoted-string that specifies how the key is      represented in the resource identified by the URI; seeSection 5      for more detail.  This attribute is OPTIONAL; its absence      indicates an implicit value of "identity".  Use of the KEYFORMAT      attribute REQUIRES a compatibility version number of 5 or greater.      KEYFORMATVERSIONS      The value is a quoted-string containing one or more positive      integers separated by the "/" character (for example, "1", "1/2",      or "1/2/5").  If more than one version of a particular KEYFORMAT      is defined, this attribute can be used to indicate which      version(s) this instance complies with.  This attribute is      OPTIONAL; if it is not present, its value is considered to be "1".      Use of the KEYFORMATVERSIONS attribute REQUIRES a compatibility      version number of 5 or greater.   If the Media Playlist file does not contain an EXT-X-KEY tag, then   Media Segments are not encrypted.   SeeSection 5 for the format of the Key file and Sections5.2,6.2.3,   and 6.3.6 for additional information on Media Segment encryption.Pantos & May                  Informational                    [Page 16]

RFC 8216                   HTTP Live Streaming               August 20174.3.2.5.  EXT-X-MAP   The EXT-X-MAP tag specifies how to obtain the Media Initialization   Section (Section 3) required to parse the applicable Media Segments.   It applies to every Media Segment that appears after it in the   Playlist until the next EXT-X-MAP tag or until the end of the   Playlist.   Its format is:   #EXT-X-MAP:<attribute-list>   The following attributes are defined:      URI      The value is a quoted-string containing a URI that identifies a      resource that contains the Media Initialization Section.  This      attribute is REQUIRED.      BYTERANGE      The value is a quoted-string specifying a byte range into the      resource identified by the URI attribute.  This range SHOULD      contain only the Media Initialization Section.  The format of the      byte range is described inSection 4.3.2.2.  This attribute is      OPTIONAL; if it is not present, the byte range is the entire      resource indicated by the URI.   An EXT-X-MAP tag SHOULD be supplied for Media Segments in Playlists   with the EXT-X-I-FRAMES-ONLY tag when the first Media Segment (i.e.,   I-frame) in the Playlist (or the first segment following an EXT-   X-DISCONTINUITY tag) does not immediately follow the Media   Initialization Section at the beginning of its resource.   Use of the EXT-X-MAP tag in a Media Playlist that contains the EXT-   X-I-FRAMES-ONLY tag REQUIRES a compatibility version number of 5 or   greater.  Use of the EXT-X-MAP tag in a Media Playlist that DOES NOT   contain the EXT-X-I-FRAMES-ONLY tag REQUIRES a compatibility version   number of 6 or greater.   If the Media Initialization Section declared by an EXT-X-MAP tag is   encrypted with a METHOD of AES-128, the IV attribute of the EXT-X-KEY   tag that applies to the EXT-X-MAP is REQUIRED.Pantos & May                  Informational                    [Page 17]

RFC 8216                   HTTP Live Streaming               August 20174.3.2.6.  EXT-X-PROGRAM-DATE-TIME   The EXT-X-PROGRAM-DATE-TIME tag associates the first sample of a   Media Segment with an absolute date and/or time.  It applies only to   the next Media Segment.  Its format is:   #EXT-X-PROGRAM-DATE-TIME:<date-time-msec>   where date-time-msec is an ISO/IEC 8601:2004 [ISO_8601] date/time   representation, such as YYYY-MM-DDThh:mm:ss.SSSZ.  It SHOULD indicate   a time zone and fractional parts of seconds, to millisecond accuracy.   For example:   #EXT-X-PROGRAM-DATE-TIME:2010-02-19T14:54:23.031+08:00   See Sections6.2.1 and6.3.3 for more information on the EXT-X-   PROGRAM-DATE-TIME tag.4.3.2.7.  EXT-X-DATERANGE   The EXT-X-DATERANGE tag associates a Date Range (i.e., a range of   time defined by a starting and ending date) with a set of attribute/   value pairs.  Its format is:   #EXT-X-DATERANGE:<attribute-list>   where the defined attributes are:      ID      A quoted-string that uniquely identifies a Date Range in the      Playlist.  This attribute is REQUIRED.      CLASS      A client-defined quoted-string that specifies some set of      attributes and their associated value semantics.  All Date Ranges      with the same CLASS attribute value MUST adhere to these      semantics.  This attribute is OPTIONAL.      START-DATE      A quoted-string containing the ISO-8601 date at which the Date      Range begins.  This attribute is REQUIRED.Pantos & May                  Informational                    [Page 18]

RFC 8216                   HTTP Live Streaming               August 2017      END-DATE      A quoted-string containing the ISO-8601 date at which the Date      Range ends.  It MUST be equal to or later than the value of the      START-DATE attribute.  This attribute is OPTIONAL.      DURATION      The duration of the Date Range expressed as a decimal-floating-      point number of seconds.  It MUST NOT be negative.  A single      instant in time (e.g., crossing a finish line) SHOULD be      represented with a duration of 0.  This attribute is OPTIONAL.      PLANNED-DURATION      The expected duration of the Date Range expressed as a decimal-      floating-point number of seconds.  It MUST NOT be negative.  This      attribute SHOULD be used to indicate the expected duration of a      Date Range whose actual duration is not yet known.  It is      OPTIONAL.      X-<client-attribute>      The "X-" prefix defines a namespace reserved for client-defined      attributes.  The client-attribute MUST be a legal AttributeName.      Clients SHOULD use a reverse-DNS syntax when defining their own      attribute names to avoid collisions.  The attribute value MUST be      a quoted-string, a hexadecimal-sequence, or a decimal-floating-      point.  An example of a client-defined attribute is X-COM-EXAMPLE-      AD-ID="XYZ123".  These attributes are OPTIONAL.      SCTE35-CMD, SCTE35-OUT, SCTE35-IN      Used to carry SCTE-35 data; seeSection 4.3.2.7.1 for more      information.  These attributes are OPTIONAL.      END-ON-NEXT      An enumerated-string whose value MUST be YES.  This attribute      indicates that the end of the range containing it is equal to the      START-DATE of its Following Range.  The Following Range is the      Date Range of the same CLASS that has the earliest START-DATE      after the START-DATE of the range in question.  This attribute is      OPTIONAL.   An EXT-X-DATERANGE tag with an END-ON-NEXT=YES attribute MUST have a   CLASS attribute.  Other EXT-X-DATERANGE tags with the same CLASS   attribute MUST NOT specify Date Ranges that overlap.Pantos & May                  Informational                    [Page 19]

RFC 8216                   HTTP Live Streaming               August 2017   An EXT-X-DATERANGE tag with an END-ON-NEXT=YES attribute MUST NOT   contain DURATION or END-DATE attributes.   A Date Range with neither a DURATION, an END-DATE, nor an END-ON-   NEXT=YES attribute has an unknown duration, even if it has a PLANNED-   DURATION.   If a Playlist contains an EXT-X-DATERANGE tag, it MUST also contain   at least one EXT-X-PROGRAM-DATE-TIME tag.   If a Playlist contains two EXT-X-DATERANGE tags with the same ID   attribute value, then any AttributeName that appears in both tags   MUST have the same AttributeValue.   If a Date Range contains both a DURATION attribute and an END-DATE   attribute, the value of the END-DATE attribute MUST be equal to the   value of the START-DATE attribute plus the value of the DURATION   attribute.   Clients SHOULD ignore EXT-X-DATERANGE tags with illegal syntax.4.3.2.7.1.  Mapping SCTE-35 into EXT-X-DATERANGE   Splice information carried in source media according to the SCTE-35   specification [SCTE35] MAY be represented in a Media Playlist using   EXT-X-DATERANGE tags.   Each SCTE-35 splice_info_section() containing a splice_null(),   splice_schedule(), bandwidth_reservation(), or private_cmd() SHOULD   be represented by an EXT-X-DATERANGE tag with an SCTE35-CMD attribute   whose value is the big-endian binary representation of the   splice_info_section(), expressed as a hexadecimal-sequence.   An SCTE-35 splice out/in pair signaled by a pair of splice_insert()   commands SHOULD be represented by one or more EXT-X-DATERANGE tags   carrying the same ID attribute, which MUST be unique to that splice   out/in pair.  The "out" splice_info_section() (with   out_of_network_indicator set to 1) MUST be placed in an SCTE35-OUT   attribute, with the same formatting as SCTE35-CMD.  The "in"   splice_info_section() (with out_of_network_indicator set to 0) MUST   be placed in an SCTE35-IN attribute, with the same formatting as   SCTE35-CMD.   An SCTE-35 splice out/in pair signaled by a pair of time_signal()   commands, each carrying a single segmentation_descriptor(), SHOULD be   represented by one or more EXT-X-DATERANGE tags carrying the same ID   attribute, which MUST be unique to that splice out/in pair.  ThePantos & May                  Informational                    [Page 20]

RFC 8216                   HTTP Live Streaming               August 2017   "out" splice_info_section() MUST be placed in an SCTE35-OUT   attribute; the "in" splice_info_section() MUST be placed in an   SCTE35-IN attribute.   Different types of segmentation, as indicated by the   segmentation_type_id in the segmentation_descriptor(), SHOULD be   represented by separate EXT-X-DATERANGE tags, even if two or more   segmentation_descriptor()s arrive in the same splice_info_section().   In that case, each EXT-X-DATERANGE tag will have an SCTE35-OUT,   SCTE35-IN, or SCTE35-CMD attribute whose value is the entire   splice_info_section().   An SCTE-35 time_signal() command that does not signal a splice out or   in point SHOULD be represented by an EXT-X-DATERANGE tag with an   SCTE35-CMD attribute.   The START-DATE of an EXT-X-DATERANGE tag containing an SCTE35-OUT   attribute MUST be the date and time that corresponds to the program   time of that splice.   The START-DATE of an EXT-X-DATERANGE tag containing an SCTE35-CMD   MUST be the date and time specified by the splice_time() in the   command or the program time at which the command appeared in the   source stream if the command does not specify a splice_time().   An EXT-X-DATERANGE tag containing an SCTE35-OUT attribute MAY contain   a PLANNED-DURATION attribute.  Its value MUST be the planned duration   of the splice.   The DURATION of an EXT-X-DATERANGE tag containing an SCTE35-IN   attribute MUST be the actual (not planned) program duration between   the corresponding out-point and that in-point.   The END-DATE of an EXT-X-DATERANGE tag containing an SCTE35-IN   attribute MUST be the actual (not planned) program date and time of   that in-point.   If the actual end date and time is not known when an SCTE35-OUT   attribute is added to the Playlist, the DURATION attribute and the   END-TIME attribute MUST NOT be present; the actual end date of the   splice SHOULD be signaled by another EXT-X-DATERANGE tag once it has   been established.   A canceled splice SHOULD NOT appear in the Playlist as an EXT-   X-DATERANGE tag.Pantos & May                  Informational                    [Page 21]

RFC 8216                   HTTP Live Streaming               August 2017   An EXT-X-DATERANGE tag announcing a splice SHOULD be added to a   Playlist at the same time as the last pre-splice Media Segment, or   earlier if possible.   The ID attribute of an EXT-X-DATERANGE tag MAY contain a   splice_event_id and/or a segmentation_event_id, but it MUST be unique   in the Playlist.  If there is a possibility that an SCTE-35 id will   be reused, the ID attribute value MUST include disambiguation, such   as a date or sequence number.4.3.3.  Media Playlist Tags   Media Playlist tags describe global parameters of the Media Playlist.   There MUST NOT be more than one Media Playlist tag of each type in   any Media Playlist.   A Media Playlist tag MUST NOT appear in a Master Playlist.4.3.3.1.  EXT-X-TARGETDURATION   The EXT-X-TARGETDURATION tag specifies the maximum Media Segment   duration.  The EXTINF duration of each Media Segment in the Playlist   file, when rounded to the nearest integer, MUST be less than or equal   to the target duration; longer segments can trigger playback stalls   or other errors.  It applies to the entire Playlist file.  Its format   is:   #EXT-X-TARGETDURATION:<s>   where s is a decimal-integer indicating the target duration in   seconds.  The EXT-X-TARGETDURATION tag is REQUIRED.4.3.3.2.  EXT-X-MEDIA-SEQUENCE   The EXT-X-MEDIA-SEQUENCE tag indicates the Media Sequence Number of   the first Media Segment that appears in a Playlist file.  Its format   is:   #EXT-X-MEDIA-SEQUENCE:<number>   where number is a decimal-integer.   If the Media Playlist file does not contain an EXT-X-MEDIA-SEQUENCE   tag, then the Media Sequence Number of the first Media Segment in the   Media Playlist SHALL be considered to be 0.  A client MUST NOT assume   that segments with the same Media Sequence Number in different Media   Playlists contain matching content (seeSection 6.3.2).Pantos & May                  Informational                    [Page 22]

RFC 8216                   HTTP Live Streaming               August 2017   A URI for a Media Segment is not required to contain its Media   Sequence Number.   See Sections6.2.1 and6.3.5 for more information on setting the EXT-   X-MEDIA-SEQUENCE tag.   The EXT-X-MEDIA-SEQUENCE tag MUST appear before the first Media   Segment in the Playlist.4.3.3.3.  EXT-X-DISCONTINUITY-SEQUENCE   The EXT-X-DISCONTINUITY-SEQUENCE tag allows synchronization between   different Renditions of the same Variant Stream or different Variant   Streams that have EXT-X-DISCONTINUITY tags in their Media Playlists.   Its format is:   #EXT-X-DISCONTINUITY-SEQUENCE:<number>   where number is a decimal-integer.   If the Media Playlist does not contain an EXT-X-DISCONTINUITY-   SEQUENCE tag, then the Discontinuity Sequence Number of the first   Media Segment in the Playlist SHALL be considered to be 0.   The EXT-X-DISCONTINUITY-SEQUENCE tag MUST appear before the first   Media Segment in the Playlist.   The EXT-X-DISCONTINUITY-SEQUENCE tag MUST appear before any EXT-   X-DISCONTINUITY tag.   See Sections6.2.1 and6.2.2 for more information about setting the   value of the EXT-X-DISCONTINUITY-SEQUENCE tag.4.3.3.4.  EXT-X-ENDLIST   The EXT-X-ENDLIST tag indicates that no more Media Segments will be   added to the Media Playlist file.  It MAY occur anywhere in the Media   Playlist file.  Its format is:   #EXT-X-ENDLISTPantos & May                  Informational                    [Page 23]

RFC 8216                   HTTP Live Streaming               August 20174.3.3.5.  EXT-X-PLAYLIST-TYPE   The EXT-X-PLAYLIST-TYPE tag provides mutability information about the   Media Playlist file.  It applies to the entire Media Playlist file.   It is OPTIONAL.  Its format is:   #EXT-X-PLAYLIST-TYPE:<type-enum>   where type-enum is either EVENT or VOD.Section 6.2.1 defines the implications of the EXT-X-PLAYLIST-TYPE   tag.   If the EXT-X-PLAYLIST-TYPE value is EVENT, Media Segments can only be   added to the end of the Media Playlist.  If the EXT-X-PLAYLIST-TYPE   value is Video On Demand (VOD), the Media Playlist cannot change.   If the EXT-X-PLAYLIST-TYPE tag is omitted from a Media Playlist, the   Playlist can be updated according to the rules inSection 6.2.1 with   no additional restrictions.  For example, a live Playlist   (Section 6.2.2) MAY be updated to remove Media Segments in the order   that they appeared.4.3.3.6.  EXT-X-I-FRAMES-ONLY   The EXT-X-I-FRAMES-ONLY tag indicates that each Media Segment in the   Playlist describes a single I-frame.  I-frames are encoded video   frames whose encoding does not depend on any other frame.  I-frame   Playlists can be used for trick play, such as fast forward, rapid   reverse, and scrubbing.   The EXT-X-I-FRAMES-ONLY tag applies to the entire Playlist.  Its   format is:   #EXT-X-I-FRAMES-ONLY   In a Playlist with the EXT-X-I-FRAMES-ONLY tag, the Media Segment   duration (EXTINF tag value) is the time between the presentation time   of the I-frame in the Media Segment and the presentation time of the   next I-frame in the Playlist, or the end of the presentation if it is   the last I-frame in the Playlist.   Media resources containing I-frame segments MUST begin with either a   Media Initialization Section (Section 3) or be accompanied by an EXT-   X-MAP tag indicating the Media Initialization Section so that clients   can load and decode I-frame segments in any order.  The byte range of   an I-frame segment with an EXT-X-BYTERANGE tag applied to it   (Section 4.3.2.2) MUST NOT include its Media Initialization Section;Pantos & May                  Informational                    [Page 24]

RFC 8216                   HTTP Live Streaming               August 2017   clients can assume that the Media Initialization Section is defined   by the EXT-X-MAP tag or is located from the start of the resource to   the offset of the first I-frame segment in that resource.   Use of the EXT-X-I-FRAMES-ONLY REQUIRES a compatibility version   number of 4 or greater.4.3.4.  Master Playlist Tags   Master Playlist tags define the Variant Streams, Renditions, and   other global parameters of the presentation.   Master Playlist tags MUST NOT appear in a Media Playlist; clients   MUST fail to parse any Playlist that contains both a Master Playlist   tag and either a Media Playlist tag or a Media Segment tag.4.3.4.1.  EXT-X-MEDIA   The EXT-X-MEDIA tag is used to relate Media Playlists that contain   alternative Renditions (Section 4.3.4.2.1) of the same content.  For   example, three EXT-X-MEDIA tags can be used to identify audio-only   Media Playlists that contain English, French, and Spanish Renditions   of the same presentation.  Or, two EXT-X-MEDIA tags can be used to   identify video-only Media Playlists that show two different camera   angles.   Its format is:   #EXT-X-MEDIA:<attribute-list>   The following attributes are defined:      TYPE      The value is an enumerated-string; valid strings are AUDIO, VIDEO,      SUBTITLES, and CLOSED-CAPTIONS.  This attribute is REQUIRED.      Typically, closed-caption [CEA608] media is carried in the video      stream.  Therefore, an EXT-X-MEDIA tag with TYPE of CLOSED-      CAPTIONS does not specify a Rendition; the closed-caption media is      present in the Media Segments of every video Rendition.      URI      The value is a quoted-string containing a URI that identifies the      Media Playlist file.  This attribute is OPTIONAL; seeSection 4.3.4.2.1.  If the TYPE is CLOSED-CAPTIONS, the URI      attribute MUST NOT be present.Pantos & May                  Informational                    [Page 25]

RFC 8216                   HTTP Live Streaming               August 2017      GROUP-ID      The value is a quoted-string that specifies the group to which the      Rendition belongs.  SeeSection 4.3.4.1.1.  This attribute is      REQUIRED.      LANGUAGE      The value is a quoted-string containing one of the standard Tags      for Identifying Languages [RFC5646], which identifies the primary      language used in the Rendition.  This attribute is OPTIONAL.      ASSOC-LANGUAGE      The value is a quoted-string containing a language tag [RFC5646]      that identifies a language that is associated with the Rendition.      An associated language is often used in a different role than the      language specified by the LANGUAGE attribute (e.g., written versus      spoken or a fallback dialect).  This attribute is OPTIONAL.      The LANGUAGE and ASSOC-LANGUAGE attributes can be used, for      example, to link Norwegian Renditions that use different spoken      and written languages.      NAME      The value is a quoted-string containing a human-readable      description of the Rendition.  If the LANGUAGE attribute is      present, then this description SHOULD be in that language.  This      attribute is REQUIRED.      DEFAULT      The value is an enumerated-string; valid strings are YES and NO.      If the value is YES, then the client SHOULD play this Rendition of      the content in the absence of information from the user indicating      a different choice.  This attribute is OPTIONAL.  Its absence      indicates an implicit value of NO.      AUTOSELECT      The value is an enumerated-string; valid strings are YES and NO.      This attribute is OPTIONAL.  Its absence indicates an implicit      value of NO.  If the value is YES, then the client MAY choose to      play this Rendition in the absence of explicit user preference      because it matches the current playback environment, such as      chosen system language.Pantos & May                  Informational                    [Page 26]

RFC 8216                   HTTP Live Streaming               August 2017      If the AUTOSELECT attribute is present, its value MUST be YES if      the value of the DEFAULT attribute is YES.      FORCED      The value is an enumerated-string; valid strings are YES and NO.      This attribute is OPTIONAL.  Its absence indicates an implicit      value of NO.  The FORCED attribute MUST NOT be present unless the      TYPE is SUBTITLES.      A value of YES indicates that the Rendition contains content that      is considered essential to play.  When selecting a FORCED      Rendition, a client SHOULD choose the one that best matches the      current playback environment (e.g., language).      A value of NO indicates that the Rendition contains content that      is intended to be played in response to explicit user request.      INSTREAM-ID      The value is a quoted-string that specifies a Rendition within the      segments in the Media Playlist.  This attribute is REQUIRED if the      TYPE attribute is CLOSED-CAPTIONS, in which case it MUST have one      of the values: "CC1", "CC2", "CC3", "CC4", or "SERVICEn" where n      MUST be an integer between 1 and 63 (e.g., "SERVICE3" or      "SERVICE42").      The values "CC1", "CC2", "CC3", and "CC4" identify a Line 21 Data      Services channel [CEA608].  The "SERVICE" values identify a      Digital Television Closed Captioning [CEA708] service block      number.      For all other TYPE values, the INSTREAM-ID MUST NOT be specified.      CHARACTERISTICS      The value is a quoted-string containing one or more Uniform Type      Identifiers [UTI] separated by comma (,) characters.  This      attribute is OPTIONAL.  Each UTI indicates an individual      characteristic of the Rendition.      A SUBTITLES Rendition MAY include the following characteristics:      "public.accessibility.transcribes-spoken-dialog",      "public.accessibility.describes-music-and-sound", and      "public.easy-to-read" (which indicates that the subtitles have      been edited for ease of reading).Pantos & May                  Informational                    [Page 27]

RFC 8216                   HTTP Live Streaming               August 2017      An AUDIO Rendition MAY include the following characteristic:      "public.accessibility.describes-video".      The CHARACTERISTICS attribute MAY include private UTIs.      CHANNELS      The value is a quoted-string that specifies an ordered, backslash-      separated ("/") list of parameters.  If the TYPE attribute is      AUDIO, then the first parameter is a count of audio channels      expressed as a decimal-integer, indicating the maximum number of      independent, simultaneous audio channels present in any Media      Segment in the Rendition.  For example, an AC-3 5.1 Rendition      would have a CHANNELS="6" attribute.  No other CHANNELS parameters      are currently defined.      All audio EXT-X-MEDIA tags SHOULD have a CHANNELS attribute.  If a      Master Playlist contains two Renditions encoded with the same      codec but a different number of channels, then the CHANNELS      attribute is REQUIRED; otherwise, it is OPTIONAL.4.3.4.1.1.  Rendition Groups   A set of one or more EXT-X-MEDIA tags with the same GROUP-ID value   and the same TYPE value defines a Group of Renditions.  Each member   of the Group MUST be an alternative Rendition of the same content;   otherwise, playback errors can occur.   All EXT-X-MEDIA tags in a Playlist MUST meet the following   constraints:   o  All EXT-X-MEDIA tags in the same Group MUST have different NAME      attributes.   o  A Group MUST NOT have more than one member with a DEFAULT      attribute of YES.   o  Each EXT-X-MEDIA tag with an AUTOSELECT=YES attribute SHOULD have      a combination of LANGUAGE [RFC5646], ASSOC-LANGUAGE, FORCED, and      CHARACTERISTICS attributes that is distinct from those of other      AUTOSELECT=YES members of its Group.   A Playlist MAY contain multiple Groups of the same TYPE in order to   provide multiple encodings of that media type.  If it does so, each   Group of the same TYPE MUST have the same set of members, and each   corresponding member MUST have identical attributes with the   exception of the URI and CHANNELS attributes.Pantos & May                  Informational                    [Page 28]

RFC 8216                   HTTP Live Streaming               August 2017   Each member in a Group of Renditions MAY have a different sample   format.  For example, an English Rendition can be encoded with AC-3   5.1 while a Spanish Rendition is encoded with AAC stereo.  However,   any EXT-X-STREAM-INF tag (Section 4.3.4.2) or EXT-X-I-FRAME-STREAM-   INF tag (Section 4.3.4.3) that references such a Group MUST have a   CODECS attribute that lists every sample format present in any   Rendition in the Group, or client playback failures can occur.  In   the example above, the CODECS attribute would include   "ac-3,mp4a.40.2".4.3.4.2.  EXT-X-STREAM-INF   The EXT-X-STREAM-INF tag specifies a Variant Stream, which is a set   of Renditions that can be combined to play the presentation.  The   attributes of the tag provide information about the Variant Stream.   The URI line that follows the EXT-X-STREAM-INF tag specifies a Media   Playlist that carries a Rendition of the Variant Stream.  The URI   line is REQUIRED.  Clients that do not support multiple video   Renditions SHOULD play this Rendition.   Its format is:   #EXT-X-STREAM-INF:<attribute-list>   <URI>   The following attributes are defined:      BANDWIDTH      The value is a decimal-integer of bits per second.  It represents      the peak segment bit rate of the Variant Stream.      If all the Media Segments in a Variant Stream have already been      created, the BANDWIDTH value MUST be the largest sum of peak      segment bit rates that is produced by any playable combination of      Renditions.  (For a Variant Stream with a single Media Playlist,      this is just the peak segment bit rate of that Media Playlist.)      An inaccurate value can cause playback stalls or prevent clients      from playing the variant.      If the Master Playlist is to be made available before all Media      Segments in the presentation have been encoded, the BANDWIDTH      value SHOULD be the BANDWIDTH value of a representative period of      similar content, encoded using the same settings.Pantos & May                  Informational                    [Page 29]

RFC 8216                   HTTP Live Streaming               August 2017      Every EXT-X-STREAM-INF tag MUST include the BANDWIDTH attribute.      AVERAGE-BANDWIDTH      The value is a decimal-integer of bits per second.  It represents      the average segment bit rate of the Variant Stream.      If all the Media Segments in a Variant Stream have already been      created, the AVERAGE-BANDWIDTH value MUST be the largest sum of      average segment bit rates that is produced by any playable      combination of Renditions.  (For a Variant Stream with a single      Media Playlist, this is just the average segment bit rate of that      Media Playlist.)  An inaccurate value can cause playback stalls or      prevent clients from playing the variant.      If the Master Playlist is to be made available before all Media      Segments in the presentation have been encoded, the AVERAGE-      BANDWIDTH value SHOULD be the AVERAGE-BANDWIDTH value of a      representative period of similar content, encoded using the same      settings.      The AVERAGE-BANDWIDTH attribute is OPTIONAL.      CODECS      The value is a quoted-string containing a comma-separated list of      formats, where each format specifies a media sample type that is      present in one or more Renditions specified by the Variant Stream.      Valid format identifiers are those in the ISO Base Media File      Format Name Space defined by "The 'Codecs' and 'Profiles'      Parameters for "Bucket" Media Types" [RFC6381].      For example, a stream containing AAC low complexity (AAC-LC) audio      and H.264 Main Profile Level 3.0 video would have a CODECS value      of "mp4a.40.2,avc1.4d401e".      Every EXT-X-STREAM-INF tag SHOULD include a CODECS attribute.      RESOLUTION      The value is a decimal-resolution describing the optimal pixel      resolution at which to display all the video in the Variant      Stream.      The RESOLUTION attribute is OPTIONAL but is recommended if the      Variant Stream includes video.Pantos & May                  Informational                    [Page 30]

RFC 8216                   HTTP Live Streaming               August 2017      FRAME-RATE      The value is a decimal-floating-point describing the maximum frame      rate for all the video in the Variant Stream, rounded to three      decimal places.      The FRAME-RATE attribute is OPTIONAL but is recommended if the      Variant Stream includes video.  The FRAME-RATE attribute SHOULD be      included if any video in a Variant Stream exceeds 30 frames per      second.      HDCP-LEVEL      The value is an enumerated-string; valid strings are TYPE-0 and      NONE.  This attribute is advisory; a value of TYPE-0 indicates      that the Variant Stream could fail to play unless the output is      protected by High-bandwidth Digital Content Protection (HDCP) Type      0 [HDCP] or equivalent.  A value of NONE indicates that the      content does not require output copy protection.      Encrypted Variant Streams with different HDCP levels SHOULD use      different media encryption keys.      The HDCP-LEVEL attribute is OPTIONAL.  It SHOULD be present if any      content in the Variant Stream will fail to play without HDCP.      Clients without output copy protection SHOULD NOT load a Variant      Stream with an HDCP-LEVEL attribute unless its value is NONE.      AUDIO      The value is a quoted-string.  It MUST match the value of the      GROUP-ID attribute of an EXT-X-MEDIA tag elsewhere in the Master      Playlist whose TYPE attribute is AUDIO.  It indicates the set of      audio Renditions that SHOULD be used when playing the      presentation.  SeeSection 4.3.4.2.1.      The AUDIO attribute is OPTIONAL.      VIDEO      The value is a quoted-string.  It MUST match the value of the      GROUP-ID attribute of an EXT-X-MEDIA tag elsewhere in the Master      Playlist whose TYPE attribute is VIDEO.  It indicates the set of      video Renditions that SHOULD be used when playing the      presentation.  SeeSection 4.3.4.2.1.      The VIDEO attribute is OPTIONAL.Pantos & May                  Informational                    [Page 31]

RFC 8216                   HTTP Live Streaming               August 2017      SUBTITLES      The value is a quoted-string.  It MUST match the value of the      GROUP-ID attribute of an EXT-X-MEDIA tag elsewhere in the Master      Playlist whose TYPE attribute is SUBTITLES.  It indicates the set      of subtitle Renditions that can be used when playing the      presentation.  SeeSection 4.3.4.2.1.      The SUBTITLES attribute is OPTIONAL.      CLOSED-CAPTIONS      The value can be either a quoted-string or an enumerated-string      with the value NONE.  If the value is a quoted-string, it MUST      match the value of the GROUP-ID attribute of an EXT-X-MEDIA tag      elsewhere in the Playlist whose TYPE attribute is CLOSED-CAPTIONS,      and it indicates the set of closed-caption Renditions that can be      used when playing the presentation.  SeeSection 4.3.4.2.1.      If the value is the enumerated-string value NONE, all EXT-X-      STREAM-INF tags MUST have this attribute with a value of NONE,      indicating that there are no closed captions in any Variant Stream      in the Master Playlist.  Having closed captions in one Variant      Stream but not another can trigger playback inconsistencies.      The CLOSED-CAPTIONS attribute is OPTIONAL.4.3.4.2.1.  Alternative Renditions   When an EXT-X-STREAM-INF tag contains an AUDIO, VIDEO, SUBTITLES, or   CLOSED-CAPTIONS attribute, it indicates that alternative Renditions   of the content are available for playback of that Variant Stream.   When defining alternative Renditions, the following constraints MUST   be met to prevent client playback errors:   o  All playable combinations of Renditions associated with an EXT-X-      STREAM-INF tag MUST have an aggregate bandwidth less than or equal      to the BANDWIDTH attribute of the EXT-X-STREAM-INF tag.   o  If an EXT-X-STREAM-INF tag contains a RESOLUTION attribute and a      VIDEO attribute, then every alternative video Rendition MUST have      an optimal display resolution matching the value of the RESOLUTION      attribute.   o  Every alternative Rendition associated with an EXT-X-STREAM-INF      tag MUST meet the constraints for a Variant Stream described inSection 6.2.4.Pantos & May                  Informational                    [Page 32]

RFC 8216                   HTTP Live Streaming               August 2017   The URI attribute of the EXT-X-MEDIA tag is REQUIRED if the media   type is SUBTITLES, but OPTIONAL if the media type is VIDEO or AUDIO.   If the media type is VIDEO or AUDIO, a missing URI attribute   indicates that the media data for this Rendition is included in the   Media Playlist of any EXT-X-STREAM-INF tag referencing this EXT-   X-MEDIA tag.  If the media TYPE is AUDIO and the URI attribute is   missing, clients MUST assume that the audio data for this Rendition   is present in every video Rendition specified by the EXT-X-STREAM-INF   tag.   The URI attribute of the EXT-X-MEDIA tag MUST NOT be included if the   media type is CLOSED-CAPTIONS.4.3.4.3.  EXT-X-I-FRAME-STREAM-INF   The EXT-X-I-FRAME-STREAM-INF tag identifies a Media Playlist file   containing the I-frames of a multimedia presentation.  It stands   alone, in that it does not apply to a particular URI in the Master   Playlist.  Its format is:   #EXT-X-I-FRAME-STREAM-INF:<attribute-list>   All attributes defined for the EXT-X-STREAM-INF tag (Section 4.3.4.2)   are also defined for the EXT-X-I-FRAME-STREAM-INF tag, except for the   FRAME-RATE, AUDIO, SUBTITLES, and CLOSED-CAPTIONS attributes.  In   addition, the following attribute is defined:      URI      The value is a quoted-string containing a URI that identifies the      I-frame Media Playlist file.  That Playlist file MUST contain an      EXT-X-I-FRAMES-ONLY tag.   Every EXT-X-I-FRAME-STREAM-INF tag MUST include a BANDWIDTH attribute   and a URI attribute.   The provisions inSection 4.3.4.2.1 also apply to EXT-X-I-FRAME-   STREAM-INF tags with a VIDEO attribute.   A Master Playlist that specifies alternative VIDEO Renditions and   I-frame Playlists SHOULD include an alternative I-frame VIDEO   Rendition for each regular VIDEO Rendition, with the same NAME and   LANGUAGE attributes.Pantos & May                  Informational                    [Page 33]

RFC 8216                   HTTP Live Streaming               August 20174.3.4.4.  EXT-X-SESSION-DATA   The EXT-X-SESSION-DATA tag allows arbitrary session data to be   carried in a Master Playlist.   Its format is:   #EXT-X-SESSION-DATA:<attribute-list>   The following attributes are defined:      DATA-ID      The value of DATA-ID is a quoted-string that identifies a      particular data value.  The DATA-ID SHOULD conform to a reverse      DNS naming convention, such as "com.example.movie.title"; however,      there is no central registration authority, so Playlist authors      SHOULD take care to choose a value that is unlikely to collide      with others.  This attribute is REQUIRED.      VALUE      VALUE is a quoted-string.  It contains the data identified by      DATA-ID.  If the LANGUAGE is specified, VALUE SHOULD contain a      human-readable string written in the specified language.      URI      The value is a quoted-string containing a URI.  The resource      identified by the URI MUST be formatted as JSON [RFC7159];      otherwise, clients may fail to interpret the resource.      LANGUAGE      The value is a quoted-string containing a language tag [RFC5646]      that identifies the language of the VALUE.  This attribute is      OPTIONAL.   Each EXT-X-SESSION-DATA tag MUST contain either a VALUE or URI   attribute, but not both.   A Playlist MAY contain multiple EXT-X-SESSION-DATA tags with the same   DATA-ID attribute.  A Playlist MUST NOT contain more than one EXT-X-   SESSION-DATA tag with the same DATA-ID attribute and the same   LANGUAGE attribute.Pantos & May                  Informational                    [Page 34]

RFC 8216                   HTTP Live Streaming               August 20174.3.4.5.  EXT-X-SESSION-KEY   The EXT-X-SESSION-KEY tag allows encryption keys from Media Playlists   to be specified in a Master Playlist.  This allows the client to   preload these keys without having to read the Media Playlist(s)   first.   Its format is:   #EXT-X-SESSION-KEY:<attribute-list>   All attributes defined for the EXT-X-KEY tag (Section 4.3.2.4) are   also defined for the EXT-X-SESSION-KEY, except that the value of the   METHOD attribute MUST NOT be NONE.  If an EXT-X-SESSION-KEY is used,   the values of the METHOD, KEYFORMAT, and KEYFORMATVERSIONS attributes   MUST match any EXT-X-KEY with the same URI value.   EXT-X-SESSION-KEY tags SHOULD be added if multiple Variant Streams or   Renditions use the same encryption keys and formats.  An EXT-X-   SESSION-KEY tag is not associated with any particular Media Playlist.   A Master Playlist MUST NOT contain more than one EXT-X-SESSION-KEY   tag with the same METHOD, URI, IV, KEYFORMAT, and KEYFORMATVERSIONS   attribute values.   The EXT-X-SESSION-KEY tag is optional.4.3.5.  Media or Master Playlist Tags   The tags in this section can appear in either Master Playlists or   Media Playlists.  If one of these tags appears in a Master Playlist,   it SHOULD NOT appear in any Media Playlist referenced by that Master   Playlist.  A tag that appears in both MUST have the same value;   otherwise, clients SHOULD ignore the value in the Media Playlist(s).   These tags MUST NOT appear more than once in a Playlist.  If a tag   appears more than once, clients MUST fail to parse the Playlist.4.3.5.1.  EXT-X-INDEPENDENT-SEGMENTS   The EXT-X-INDEPENDENT-SEGMENTS tag indicates that all media samples   in a Media Segment can be decoded without information from other   segments.  It applies to every Media Segment in the Playlist.   Its format is:   #EXT-X-INDEPENDENT-SEGMENTSPantos & May                  Informational                    [Page 35]

RFC 8216                   HTTP Live Streaming               August 2017   If the EXT-X-INDEPENDENT-SEGMENTS tag appears in a Master Playlist,   it applies to every Media Segment in every Media Playlist in the   Master Playlist.4.3.5.2.  EXT-X-START   The EXT-X-START tag indicates a preferred point at which to start   playing a Playlist.  By default, clients SHOULD start playback at   this point when beginning a playback session.  This tag is OPTIONAL.   Its format is:   #EXT-X-START:<attribute-list>   The following attributes are defined:      TIME-OFFSET      The value of TIME-OFFSET is a signed-decimal-floating-point number      of seconds.  A positive number indicates a time offset from the      beginning of the Playlist.  A negative number indicates a negative      time offset from the end of the last Media Segment in the      Playlist.  This attribute is REQUIRED.      The absolute value of TIME-OFFSET SHOULD NOT be larger than the      Playlist duration.  If the absolute value of TIME-OFFSET exceeds      the duration of the Playlist, it indicates either the end of the      Playlist (if positive) or the beginning of the Playlist (if      negative).      If the Playlist does not contain the EXT-X-ENDLIST tag, the TIME-      OFFSET SHOULD NOT be within three target durations of the end of      the Playlist file.      PRECISE      The value is an enumerated-string; valid strings are YES and NO.      If the value is YES, clients SHOULD start playback at the Media      Segment containing the TIME-OFFSET, but SHOULD NOT render media      samples in that segment whose presentation times are prior to the      TIME-OFFSET.  If the value is NO, clients SHOULD attempt to render      every media sample in that segment.  This attribute is OPTIONAL.      If it is missing, its value should be treated as NO.Pantos & May                  Informational                    [Page 36]

RFC 8216                   HTTP Live Streaming               August 20175.  Key Files5.1.  Structure of Key Files   An EXT-X-KEY tag with a URI attribute identifies a Key file.  A Key   file contains a cipher key that can decrypt Media Segments in the   Playlist.   [AES_128] encryption uses 16-octet keys.  If the KEYFORMAT of an EXT-   X-KEY tag is "identity", the Key file is a single packed array of 16   octets in binary format.5.2.  IV for AES-128   [AES_128] REQUIRES the same 16-octet IV to be supplied when   encrypting and decrypting.  Varying this IV increases the strength of   the cipher.   An IV attribute on an EXT-X-KEY tag with a KEYFORMAT of "identity"   specifies an IV that can be used when decrypting Media Segments   encrypted with that Key file.  IV values for AES-128 are 128-bit   numbers.   An EXT-X-KEY tag with a KEYFORMAT of "identity" that does not have an   IV attribute indicates that the Media Sequence Number is to be used   as the IV when decrypting a Media Segment, by putting its big-endian   binary representation into a 16-octet (128-bit) buffer and padding   (on the left) with zeros.6.  Client/Server Responsibilities6.1.  Introduction   This section describes how the server generates the Playlist and   Media Segments and how the client should download them for playback.6.2.  Server Responsibilities6.2.1.  General Server Responsibilities   The production of the source media is outside the scope of this   document, which simply presumes a source of continuous encoded media   containing the presentation.   The server MUST divide the source media into individual Media   Segments whose duration is less than or equal to a constant target   duration.  Segments that are longer than the planned target duration   can trigger playback stalls and other errors.Pantos & May                  Informational                    [Page 37]

RFC 8216                   HTTP Live Streaming               August 2017   The server SHOULD attempt to divide the source media at points that   support effective decode of individual Media Segments, e.g., on   packet and key frame boundaries.   The server MUST create a URI for every Media Segment that enables its   clients to obtain the segment data.  If a server supports partial   loading of resources (e.g., via HTTP Range requests), it MAY specify   segments as sub-ranges of larger resources using the EXT-X-BYTERANGE   tag.   Any Media Segment that is specified in a Playlist loaded by a client   MUST be available for immediate download, or playback errors can   occur.  Once download starts, its transfer rate SHOULD NOT be   constrained by the segment production process.   HTTP servers SHOULD transfer text files -- such as Playlists and   WebVTT segments -- using the "gzip" Content-Encoding if the client   indicates that it is prepared to accept it.   The server must create a Media Playlist file (Section 4) that   contains a URI for each Media Segment that the server wishes to make   available, in the order in which they are to be played.   The value of the EXT-X-VERSION tag (Section 4.3.1.2) SHOULD NOT be   greater than what is required for the tags and attributes in the   Playlist (seeSection 7).   Changes to the Playlist file MUST be made atomically from the point   of view of the clients, or playback errors MAY occur.   The server MUST NOT change the Media Playlist file, except to:   o  Append lines to it (Section 6.2.1).   o  Remove Media Segment URIs from the Playlist in the order that they      appear, along with any tags that apply only to those segments      (Section 6.2.2).   o  Increment the value of the EXT-X-MEDIA-SEQUENCE or EXT-X-      DISCONTINUITY-SEQUENCE tags (Section 6.2.2).   o  Add an EXT-X-ENDLIST tag to the Playlist (Section 6.2.1).Pantos & May                  Informational                    [Page 38]

RFC 8216                   HTTP Live Streaming               August 2017   A Media Playlist has further constraints on its updates if it   contains an EXT-X-PLAYLIST-TYPE tag.  An EXT-X-PLAYLIST-TYPE tag with   a value of VOD indicates that the Playlist file MUST NOT change.  An   EXT-X-PLAYLIST-TYPE tag with a value of EVENT indicates that the   server MUST NOT change or delete any part of the Playlist file; it   MAY append lines to it.   The value of the EXT-X-TARGETDURATION tag in the Media Playlist MUST   NOT change.  A typical target duration is 10 seconds.   Playlist changes other than those allowed here can trigger playback   errors and inconsistent client behavior.   Each Media Segment in a Media Playlist has an integer Discontinuity   Sequence Number.  The Discontinuity Sequence Number can be used in   addition to the timestamps within the media to synchronize Media   Segments across different Renditions.   A segment's Discontinuity Sequence Number is the value of the EXT-X-   DISCONTINUITY-SEQUENCE tag (or zero if none) plus the number of EXT-   X-DISCONTINUITY tags in the Playlist preceding the URI line of the   segment.   The server MAY associate an absolute date and time with a Media   Segment by applying an EXT-X-PROGRAM-DATE-TIME tag to it.  This   defines an informative mapping of the (wall-clock) date and time   specified by the tag to the first media timestamp in the segment,   which may be used as a basis for seeking, for display, or for other   purposes.  If a server provides this mapping, it SHOULD apply an EXT-   X-PROGRAM-DATE-TIME tag to every segment that has an EXT-   X-DISCONTINUITY tag applied to it.   The Server MUST NOT add any EXT-X-PROGRAM-DATE-TIME tag to a Playlist   that would cause the mapping between program date and Media Segment   to become ambiguous.   The server MUST NOT remove an EXT-X-DATERANGE tag from a Playlist if   any date in the range maps to a Media Segment in the Playlist.   The server MUST NOT reuse the ID attribute value of an EXT-   X-DATERANGE tag for any new Date Range in the same Playlist.   Once the Following Range of a Date Range with an END-ON-NEXT=YES   attribute is added to a Playlist, the Server MUST NOT subsequently   add a Date Range with the same CLASS attribute whose START-DATE is   between that of the END-ON-NEXT=YES range and its Following Range.Pantos & May                  Informational                    [Page 39]

RFC 8216                   HTTP Live Streaming               August 2017   For Date Ranges with a PLANNED-DURATION attribute, the Server SHOULD   signal the actual end of the range once it has been established.  It   can do so by adding another EXT-X-DATERANGE tag with the same ID   attribute value and either a DURATION or an END-DATE attribute or, if   the Date Range has an END-ON-NEXT=YES attribute, by adding a   Following Range.   If the Media Playlist contains the final Media Segment of the   presentation, then the Playlist file MUST contain the EXT-X-ENDLIST   tag; this allows clients to minimize unproductive Playlist reloads.   If a Media Playlist does not contain the EXT-X-ENDLIST tag, the   server MUST make a new version of the Playlist file available that   contains at least one new Media Segment.  It MUST be made available   relative to the time that the previous version of the Playlist file   was made available: no earlier than one-half the target duration   after that time, and no later than 1.5 times the target duration   after that time.  This allows clients to utilize the network   efficiently.   If the server wishes to remove an entire presentation, it SHOULD   provide a clear indication to clients that the Playlist file is no   longer available (e.g., with an HTTP 404 or 410 response).  It MUST   ensure that all Media Segments in the Playlist file remain available   to clients for at least the duration of the Playlist file at the time   of removal to prevent interruption of in-progress playback.6.2.2.  Live Playlists   The server MAY limit the availability of Media Segments by removing   Media Segments from the Playlist file (Section 6.2.1).  If Media   Segments are to be removed, the Playlist file MUST contain an EXT-X-   MEDIA-SEQUENCE tag.  Its value MUST be incremented by 1 for every   Media Segment that is removed from the Playlist file; it MUST NOT   decrease or wrap.  Clients can malfunction if each Media Segment does   not have a consistent, unique Media Sequence Number.   Media Segments MUST be removed from the Playlist file in the order   that they appear in the Playlist; otherwise, client playback can   malfunction.   The server MUST NOT remove a Media Segment from a Playlist file   without an EXT-X-ENDLIST tag if that would produce a Playlist whose   duration is less than three times the target duration.  Doing so can   trigger playback stalls.Pantos & May                  Informational                    [Page 40]

RFC 8216                   HTTP Live Streaming               August 2017   When the server removes a Media Segment URI from the Playlist, the   corresponding Media Segment MUST remain available to clients for a   period of time equal to the duration of the segment plus the duration   of the longest Playlist file distributed by the server containing   that segment.  Removing a Media Segment earlier than that can   interrupt in-progress playback.   If the server wishes to remove segments from a Media Playlist   containing an EXT-X-DISCONTINUITY tag, the Media Playlist MUST   contain an EXT-X-DISCONTINUITY-SEQUENCE tag.  Without the EXT-X-   DISCONTINUITY-SEQUENCE tag, it can be impossible for a client to   locate corresponding segments between Renditions.   If the server removes an EXT-X-DISCONTINUITY tag from the Media   Playlist, it MUST increment the value of the EXT-X-DISCONTINUITY-   SEQUENCE tag so that the Discontinuity Sequence Numbers of the   segments still in the Media Playlist remain unchanged.  The value of   the EXT-X-DISCONTINUITY-SEQUENCE tag MUST NOT decrease or wrap.   Clients can malfunction if each Media Segment does not have a   consistent Discontinuity Sequence Number.   If a server plans to remove a Media Segment after it is delivered to   clients over HTTP, it SHOULD ensure that the HTTP response contains   an Expires header that reflects the planned time-to-live.   A Live Playlist MUST NOT contain the EXT-X-PLAYLIST-TYPE tag, as no   value of that tag allows Media Segments to be removed.6.2.3.  Encrypting Media Segments   Media Segments MAY be encrypted.  Every encrypted Media Segment MUST   have an EXT-X-KEY tag (Section 4.3.2.4) applied to it with a URI that   the client can use to obtain a Key file (Section 5) containing the   decryption key.   A Media Segment can only be encrypted with one encryption METHOD,   using one encryption key and IV.  However, a server MAY offer   multiple ways to retrieve that key by providing multiple EXT-X-KEY   tags, each with a different KEYFORMAT attribute value.   The server MAY set the HTTP Expires header in the key response to   indicate the duration for which the key can be cached.   Any unencrypted Media Segment in a Playlist that is preceded by an   encrypted Media Segment MUST have an EXT-X-KEY tag applied to it with   a METHOD attribute of NONE.  Otherwise, the client will misinterpret   those segments as encrypted.Pantos & May                  Informational                    [Page 41]

RFC 8216                   HTTP Live Streaming               August 2017   If the encryption METHOD is AES-128 and the Playlist does not contain   the EXT-X-I-FRAMES-ONLY tag, AES encryption as described inSection 4.3.2.4 SHALL be applied to individual Media Segments.   If the encryption METHOD is AES-128 and the Playlist contains an EXT-   X-I-FRAMES-ONLY tag, the entire resource MUST be encrypted using   AES-128 CBC with PKCS7 padding [RFC5652].  Encryption MAY be   restarted on 16-byte block boundaries, unless the first block   contains an I-frame.  The IV used for encryption MUST be either the   Media Sequence Number of the Media Segment or the value of the IV   attribute of the EXT-X-KEY tag, as described inSection 5.2.  These   constraints allow a client to load and decrypt individual I-frames   specified as sub-ranges of regular encrypted Media Segments, and   their Media Initialization Sections.   If the encryption METHOD is SAMPLE-AES, media samples MAY be   encrypted prior to encapsulation in a Media Segment.   The server MUST NOT remove an EXT-X-KEY tag from the Playlist file if   it applies to any Media Segment in the Playlist file, or clients who   subsequently load that Playlist will be unable to decrypt those Media   Segments.6.2.4.  Providing Variant Streams   A server MAY offer multiple Media Playlist files to provide different   encodings of the same presentation.  If it does so, it SHOULD provide   a Master Playlist file that lists each Variant Stream to allow   clients to switch between encodings dynamically.   Master Playlists describe regular Variant Streams with EXT-X-STREAM-   INF tags and I-frame Variant Streams with EXT-X-I-FRAME-STREAM-INF   tags.   If an EXT-X-STREAM-INF tag or EXT-X-I-FRAME-STREAM-INF tag contains   the CODECS attribute, the attribute value MUST include every media   format [RFC6381] present in any Media Segment in any of the   Renditions specified by the Variant Stream.Pantos & May                  Informational                    [Page 42]

RFC 8216                   HTTP Live Streaming               August 2017   The server MUST meet the following constraints when producing Variant   Streams in order to allow clients to switch between them seamlessly:   o  Each Variant Stream MUST present the same content.   o  Matching content in Variant Streams MUST have matching timestamps.      This allows clients to synchronize the media.   o  Matching content in Variant Streams MUST have matching      Discontinuity Sequence Numbers (seeSection 4.3.3.3).   o  Each Media Playlist in each Variant Stream MUST have the same      target duration.  The only exceptions are SUBTITLES Renditions and      Media Playlists containing an EXT-X-I-FRAMES-ONLY tag, which MAY      have different target durations if they have an EXT-X-PLAYLIST-      TYPE of VOD.   o  Content that appears in a Media Playlist of one Variant Stream but      not in another MUST appear either at the beginning or at the end      of the Media Playlist file and MUST NOT be longer than the target      duration.   o  If any Media Playlists have an EXT-X-PLAYLIST-TYPE tag, all Media      Playlists MUST have an EXT-X-PLAYLIST-TYPE tag with the same      value.   o  If the Playlist contains an EXT-X-PLAYLIST-TYPE tag with the value      of VOD, the first segment of every Media Playlist in every Variant      Stream MUST start at the same media timestamp.   o  If any Media Playlist in a Master Playlist contains an EXT-X-      PROGRAM-DATE-TIME tag, then all Media Playlists in that Master      Playlist MUST contain EXT-X-PROGRAM-DATE-TIME tags with consistent      mappings of date and time to media timestamps.   o  Each Variant Stream MUST contain the same set of Date Ranges, each      one identified by an EXT-X-DATERANGE tag(s) with the same ID      attribute value and containing the same set of attribute/value      pairs.   In addition, for broadest compatibility, Variant Streams SHOULD   contain the same encoded audio bitstream.  This allows clients to   switch between Variant Streams without audible glitching.   The rules for Variant Streams also apply to alternative Renditions   (seeSection 4.3.4.2.1).Pantos & May                  Informational                    [Page 43]

RFC 8216                   HTTP Live Streaming               August 20176.3.  Client Responsibilities6.3.1.  General Client Responsibilities   How the client obtains the URI to the Playlist file is outside the   scope of this document; it is presumed to have done so.   The client obtains the Playlist file from the URI.  If the Playlist   file so obtained is a Master Playlist, the client can select a   Variant Stream to load from the Master Playlist.   Clients MUST ensure that loaded Playlists comply withSection 4 and   that the EXT-X-VERSION tag, if present, specifies a protocol version   supported by the client; if either check fails, the client MUST NOT   attempt to use the Playlist, or unintended behavior could occur.   If any URI element in a Playlist contains an URI scheme that the   client cannot handle, the client MUST stop playback.  All clients   MUST support HTTP schemes.   To support forward compatibility, when parsing Playlists, clients   MUST:   o  ignore any unrecognized tags.   o  ignore any attribute/value pair with an unrecognized      AttributeName.   o  ignore any tag containing an attribute/value pair of type      enumerated-string whose AttributeName is recognized but whose      AttributeValue is not recognized, unless the definition of the      attribute says otherwise.   Algorithms used by the client to switch between Variant Streams are   beyond the scope of this document.6.3.2.  Loading the Media Playlist File   Every time a Media Playlist is loaded or reloaded from a Playlist   URI, the client MUST determine the next Media Segment to load, as   described inSection 6.3.5, if it intends to play the presentation   normally (i.e., in Playlist order at the nominal playback rate).   If the Media Playlist contains the EXT-X-MEDIA-SEQUENCE tag, the   client SHOULD assume that each Media Segment in it will become   unavailable at the time that the Playlist file was loaded plus the   duration of the Playlist file.Pantos & May                  Informational                    [Page 44]

RFC 8216                   HTTP Live Streaming               August 2017   A client MAY use the segment Media Sequence Number to track the   location of a Media Segment within a Playlist when the Playlist is   reloaded.   A client MUST NOT assume that segments with the same Media Sequence   Number in different Variant Streams or Renditions have the same   position in the presentation; Playlists MAY have independent Media   Sequence Numbers.  Instead, a client MUST use the relative position   of each segment on the Playlist timeline and its Discontinuity   Sequence Number to locate corresponding segments.   A client MUST load the Media Playlist file of every Rendition   selected for playback in order to locate the media specific to that   Rendition.  But, to prevent unnecessary load on the server, it SHOULD   NOT load the Playlist file of any other Rendition.   For some Variant Streams, it is possible to select Renditions that do   not include the Rendition specified by the EXT-X-STREAM-INF tag.  As   noted above, the client SHOULD NOT load that Rendition in those   cases.6.3.3.  Playing the Media Playlist File   The client SHALL choose which Media Segment to play first from the   Media Playlist when playback starts.  If the EXT-X-ENDLIST tag is not   present and the client intends to play the media normally, the client   SHOULD NOT choose a segment that starts less than three target   durations from the end of the Playlist file.  Doing so can trigger   playback stalls.   Normal playback can be achieved by playing the Media Segments in the   order that they appear in the Playlist.  The client MAY present the   available media in any way it wishes, including normal playback,   random access, and trick modes.   The encoding parameters for samples in a Media Segment and across   multiple Media Segments in a Media Playlist SHOULD remain consistent.   However, clients SHOULD deal with encoding changes as they are   encountered, for example, by scaling video content to accommodate a   resolution change.  If the Variant Stream includes a RESOLUTION   attribute, clients SHOULD display all video within a rectangle with   the same proportions as that resolution.   Clients SHOULD be prepared to handle multiple tracks of a particular   type (e.g., audio or video).  A client with no other preference   SHOULD choose the track with the lowest numerical track identifier   that it can play.Pantos & May                  Informational                    [Page 45]

RFC 8216                   HTTP Live Streaming               August 2017   Clients SHOULD ignore private streams inside Transport Streams that   they do not recognize.  Private streams can be used to support   different devices with the same stream, although stream authors   SHOULD be sensitive to the additional network load that this imposes.   The client MUST be prepared to reset its parser(s) and decoder(s)   before playing a Media Segment that has an EXT-X-DISCONTINUITY tag   applied to it; otherwise, playback errors can occur.   The client SHOULD attempt to load Media Segments in advance of when   they will be required for uninterrupted playback to compensate for   temporary variations in latency and throughput.   The client MAY use the value of the EXT-X-PROGRAM-DATE-TIME tag to   display the program origination time to the user.  If the value   includes time zone information, the client SHALL take it into   account; if it does not, the client MAY assume the time to be local.   Note that dates in Playlists can refer to when the content was   produced (or to other times), which have no relation to the time of   playback.   If the first EXT-X-PROGRAM-DATE-TIME tag in a Playlist appears after   one or more Media Segment URIs, the client SHOULD extrapolate   backward from that tag (using EXTINF durations and/or media   timestamps) to associate dates with those segments.  To associate a   date with any other Media Segment that does not have an EXT-X-   PROGRAM-DATE-TIME tag applied to it directly, the client SHOULD   extrapolate forward from the last EXT-X-PROGRAM-DATE-TIME tag   appearing before that segment in the Playlist.6.3.4.  Reloading the Media Playlist File   The client MUST periodically reload a Media Playlist file to learn   what media is currently available, unless it contains an EXT-X-   PLAYLIST-TYPE tag with a value of VOD, or a value of EVENT and the   EXT-X-ENDLIST tag is also present.   However, the client MUST NOT attempt to reload the Playlist file more   frequently than specified by this section, in order to limit the   collective load on the server.   When a client loads a Playlist file for the first time or reloads a   Playlist file and finds that it has changed since the last time it   was loaded, the client MUST wait for at least the target duration   before attempting to reload the Playlist file again, measured from   the last time the client began loading the Playlist file.Pantos & May                  Informational                    [Page 46]

RFC 8216                   HTTP Live Streaming               August 2017   If the client reloads a Playlist file and finds that it has not   changed, then it MUST wait for a period of one-half the target   duration before retrying.   After reloading a Media Playlist, the client SHOULD verify that each   Media Segment in it has the same URI (and byte range, if specified)   as the Media Segment with the same Media Sequence Number in the   previous Media Playlist.  It SHOULD halt playback if it does not, as   this normally indicates a server error.   In order to reduce server load, the client SHOULD NOT reload the   Playlist files of Variant Streams or alternate Renditions that are   not currently being played.  If it decides to switch playback to a   different Variant Stream, it SHOULD stop reloading the Playlist of   the old Variant Stream and begin loading the Playlist of the new   Variant Stream.  It can use the EXTINF durations and the constraints   inSection 6.2.4 to determine the approximate location of   corresponding media.  Once media from the new Variant Stream has been   loaded, the timestamps in the Media Segments can be used to   synchronize the old and new timelines precisely.   A client MUST NOT attempt to use the Media Sequence Number to   synchronize between streams (seeSection 6.3.2).6.3.5.  Determining the Next Segment to Load   The client MUST examine the Media Playlist file every time it is   loaded or reloaded to determine the next Media Segment to load, as   the set of available media MAY have changed.   The first segment to load is generally the segment that the client   has chosen to play first (seeSection 6.3.3).   In order to play the presentation normally, the next Media Segment to   load is the one with the lowest Media Sequence Number that is greater   than the Media Sequence Number of the last Media Segment loaded.6.3.6.  Decrypting Encrypted Media Segments   If a Media Playlist file contains an EXT-X-KEY tag that specifies a   Key file URI, the client can obtain that Key file and use the key   inside it to decrypt all Media Segments to which that EXT-X-KEY tag   applies.Pantos & May                  Informational                    [Page 47]

RFC 8216                   HTTP Live Streaming               August 2017   A client MUST ignore any EXT-X-KEY tag with an unsupported or   unrecognized KEYFORMAT attribute, to allow for cross-device   addressability.  If the Playlist contains a Media Segment to which   only EXT-X-KEY tags with unrecognized or unsupported KEYFORMAT   attributes are applied, playback SHOULD fail.   A client MUST NOT attempt to decrypt any segments whose EXT-X-KEY tag   has a METHOD attribute that it does not recognize.   If the encryption METHOD is AES-128, AES-128 CBC decryption SHALL be   applied to individual Media Segments, whose encryption format is   described inSection 4.3.2.4.   If the encryption METHOD is AES-128 and the Media Segment is part of   an I-frame Playlist (Section 4.3.3.6) and it has an EXT-X-BYTERANGE   tag applied to it, special care needs to be taken in loading and   decrypting the segment, because the resource identified by the URI is   encrypted in 16-byte blocks from the start of the resource.   The decrypted I-frame can be recovered by first widening its byte   range, as specified by the EXT-X-BYTERANGE tag, so that it starts and   ends on 16-byte boundaries from the start of the resource.   Next, the byte range is widened further to include a 16-byte block at   the beginning of the range.  This 16-byte block allows the correct IV   for the following block to be calculated.   The widened byte range can then be loaded and decrypted with AES-128   CBC using an arbitrary IV.  The number of bytes added to the   beginning and the end of the original byte range are discarded from   the decrypted bytes; what remains is the decrypted I-frame.   If the encryption METHOD is SAMPLE-AES, AES-128 decryption SHALL be   applied to encrypted media samples within the Media Segment.   An EXT-X-KEY tag with a METHOD of NONE indicates that the Media   Segments it applies to are not encrypted.7.  Protocol Version Compatibility   Protocol compatibility is specified by the EXT-X-VERSION tag.  A   Playlist that contains tags or attributes that are not compatible   with protocol version 1 MUST include an EXT-X-VERSION tag.   A client MUST NOT attempt playback if it does not support the   protocol version specified by the EXT-X-VERSION tag, or unintended   behavior could occur.Pantos & May                  Informational                    [Page 48]

RFC 8216                   HTTP Live Streaming               August 2017   A Media Playlist MUST indicate an EXT-X-VERSION of 2 or higher if it   contains:   o  The IV attribute of the EXT-X-KEY tag.   A Media Playlist MUST indicate an EXT-X-VERSION of 3 or higher if it   contains:   o  Floating-point EXTINF duration values.   A Media Playlist MUST indicate an EXT-X-VERSION of 4 or higher if it   contains:   o  The EXT-X-BYTERANGE tag.   o  The EXT-X-I-FRAMES-ONLY tag.   A Media Playlist MUST indicate an EXT-X-VERSION of 5 or higher if it   contains:   o  The KEYFORMAT and KEYFORMATVERSIONS attributes of the EXT-X-KEY      tag.   o  The EXT-X-MAP tag.   A Media Playlist MUST indicate an EXT-X-VERSION of 6 or higher if it   contains:   o  The EXT-X-MAP tag in a Media Playlist that does not contain EXT-      X-I-FRAMES-ONLY.   A Master Playlist MUST indicate an EXT-X-VERSION of 7 or higher if it   contains:   o  "SERVICE" values for the INSTREAM-ID attribute of the EXT-X-MEDIA      tag.   The EXT-X-MEDIA tag and the AUDIO, VIDEO, and SUBTITLES attributes of   the EXT-X-STREAM-INF tag are backward compatible to protocol version   1, but playback on older clients may not be desirable.  A server MAY   consider indicating an EXT-X-VERSION of 4 or higher in the Master   Playlist but is not required to do so.   The PROGRAM-ID attribute of the EXT-X-STREAM-INF and the EXT-X-I-   FRAME-STREAM-INF tags was removed in protocol version 6.   The EXT-X-ALLOW-CACHE tag was removed in protocol version 7.Pantos & May                  Informational                    [Page 49]

RFC 8216                   HTTP Live Streaming               August 20178.  Playlist Examples8.1.  Simple Media Playlist   #EXTM3U   #EXT-X-TARGETDURATION:10   #EXT-X-VERSION:3   #EXTINF:9.009,   http://media.example.com/first.ts   #EXTINF:9.009,   http://media.example.com/second.ts   #EXTINF:3.003,   http://media.example.com/third.ts   #EXT-X-ENDLIST8.2.  Live Media Playlist Using HTTPS   #EXTM3U   #EXT-X-VERSION:3   #EXT-X-TARGETDURATION:8   #EXT-X-MEDIA-SEQUENCE:2680   #EXTINF:7.975,   https://priv.example.com/fileSequence2680.ts   #EXTINF:7.941,   https://priv.example.com/fileSequence2681.ts   #EXTINF:7.975,   https://priv.example.com/fileSequence2682.tsPantos & May                  Informational                    [Page 50]

RFC 8216                   HTTP Live Streaming               August 20178.3.  Playlist with Encrypted Media Segments   #EXTM3U   #EXT-X-VERSION:3   #EXT-X-MEDIA-SEQUENCE:7794   #EXT-X-TARGETDURATION:15   #EXT-X-KEY:METHOD=AES-128,URI="https://priv.example.com/key.php?r=52"   #EXTINF:2.833,   http://media.example.com/fileSequence52-A.ts   #EXTINF:15.0,   http://media.example.com/fileSequence52-B.ts   #EXTINF:13.333,   http://media.example.com/fileSequence52-C.ts   #EXT-X-KEY:METHOD=AES-128,URI="https://priv.example.com/key.php?r=53"   #EXTINF:15.0,   http://media.example.com/fileSequence53-A.ts8.4.  Master Playlist   #EXTM3U   #EXT-X-STREAM-INF:BANDWIDTH=1280000,AVERAGE-BANDWIDTH=1000000   http://example.com/low.m3u8   #EXT-X-STREAM-INF:BANDWIDTH=2560000,AVERAGE-BANDWIDTH=2000000   http://example.com/mid.m3u8   #EXT-X-STREAM-INF:BANDWIDTH=7680000,AVERAGE-BANDWIDTH=6000000   http://example.com/hi.m3u8   #EXT-X-STREAM-INF:BANDWIDTH=65000,CODECS="mp4a.40.5"   http://example.com/audio-only.m3u88.5.  Master Playlist with I-Frames   #EXTM3U   #EXT-X-STREAM-INF:BANDWIDTH=1280000   low/audio-video.m3u8   #EXT-X-I-FRAME-STREAM-INF:BANDWIDTH=86000,URI="low/iframe.m3u8"   #EXT-X-STREAM-INF:BANDWIDTH=2560000   mid/audio-video.m3u8   #EXT-X-I-FRAME-STREAM-INF:BANDWIDTH=150000,URI="mid/iframe.m3u8"   #EXT-X-STREAM-INF:BANDWIDTH=7680000   hi/audio-video.m3u8   #EXT-X-I-FRAME-STREAM-INF:BANDWIDTH=550000,URI="hi/iframe.m3u8"   #EXT-X-STREAM-INF:BANDWIDTH=65000,CODECS="mp4a.40.5"   audio-only.m3u8Pantos & May                  Informational                    [Page 51]

RFC 8216                   HTTP Live Streaming               August 20178.6.  Master Playlist with Alternative Audio   In this example, the CODECS attributes have been condensed for space.   A '\' is used to indicate that the tag continues on the following   line with whitespace removed:   #EXTM3U   #EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="aac",NAME="English", \      DEFAULT=YES,AUTOSELECT=YES,LANGUAGE="en", \      URI="main/english-audio.m3u8"   #EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="aac",NAME="Deutsch", \      DEFAULT=NO,AUTOSELECT=YES,LANGUAGE="de", \      URI="main/german-audio.m3u8"   #EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="aac",NAME="Commentary", \      DEFAULT=NO,AUTOSELECT=NO,LANGUAGE="en", \      URI="commentary/audio-only.m3u8"   #EXT-X-STREAM-INF:BANDWIDTH=1280000,CODECS="...",AUDIO="aac"   low/video-only.m3u8   #EXT-X-STREAM-INF:BANDWIDTH=2560000,CODECS="...",AUDIO="aac"   mid/video-only.m3u8   #EXT-X-STREAM-INF:BANDWIDTH=7680000,CODECS="...",AUDIO="aac"   hi/video-only.m3u8   #EXT-X-STREAM-INF:BANDWIDTH=65000,CODECS="mp4a.40.5",AUDIO="aac"   main/english-audio.m3u88.7.  Master Playlist with Alternative Video   This example shows three different video Renditions (Main,   Centerfield, and Dugout) and three different Variant Streams (low,   mid, and high).  In this example, clients that did not support the   EXT-X-MEDIA tag and the VIDEO attribute of the EXT-X-STREAM-INF tag   would only be able to play the video Rendition "Main".   Since the EXT-X-STREAM-INF tag has no AUDIO attribute, all video   Renditions would be required to contain the audio.Pantos & May                  Informational                    [Page 52]

RFC 8216                   HTTP Live Streaming               August 2017   In this example, the CODECS attributes have been condensed for space.   A '\' is used to indicate that the tag continues on the following   line with whitespace removed:   #EXTM3U   #EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="low",NAME="Main", \      DEFAULT=YES,URI="low/main/audio-video.m3u8"   #EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="low",NAME="Centerfield", \      DEFAULT=NO,URI="low/centerfield/audio-video.m3u8"   #EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="low",NAME="Dugout", \      DEFAULT=NO,URI="low/dugout/audio-video.m3u8"   #EXT-X-STREAM-INF:BANDWIDTH=1280000,CODECS="...",VIDEO="low"   low/main/audio-video.m3u8   #EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="mid",NAME="Main", \      DEFAULT=YES,URI="mid/main/audio-video.m3u8"   #EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="mid",NAME="Centerfield", \      DEFAULT=NO,URI="mid/centerfield/audio-video.m3u8"   #EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="mid",NAME="Dugout", \      DEFAULT=NO,URI="mid/dugout/audio-video.m3u8"   #EXT-X-STREAM-INF:BANDWIDTH=2560000,CODECS="...",VIDEO="mid"   mid/main/audio-video.m3u8   #EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="hi",NAME="Main", \      DEFAULT=YES,URI="hi/main/audio-video.m3u8"   #EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="hi",NAME="Centerfield", \      DEFAULT=NO,URI="hi/centerfield/audio-video.m3u8"   #EXT-X-MEDIA:TYPE=VIDEO,GROUP-ID="hi",NAME="Dugout", \      DEFAULT=NO,URI="hi/dugout/audio-video.m3u8"   #EXT-X-STREAM-INF:BANDWIDTH=7680000,CODECS="...",VIDEO="hi"   hi/main/audio-video.m3u88.8.  Session Data in a Master Playlist   In this example, only the EXT-X-SESSION-DATA is shown:   #EXT-X-SESSION-DATA:DATA-ID="com.example.lyrics",URI="lyrics.json"   #EXT-X-SESSION-DATA:DATA-ID="com.example.title",LANGUAGE="en", \           VALUE="This is an example"   #EXT-X-SESSION-DATA:DATA-ID="com.example.title",LANGUAGE="es", \           VALUE="Este es un ejemplo"Pantos & May                  Informational                    [Page 53]

RFC 8216                   HTTP Live Streaming               August 20178.9.  CHARACTERISTICS Attribute Containing Multiple Characteristics   Certain characteristics are valid in combination, as in:   CHARACTERISTICS=   "public.accessibility.transcribes-spoken-dialog,public.easy-to-read"8.10.  EXT-X-DATERANGE Carrying SCTE-35 Tags   This example shows two EXT-X-DATERANGE tags that describe a single   Date Range, with an SCTE-35 "out" splice_insert() command that is   subsequently updated with an SCTE-35 "in" splice_insert() command.   #EXTM3U   ...   #EXT-X-DATERANGE:ID="splice-6FFFFFF0",START-DATE="2014-03-05T11:   15:00Z",PLANNED-DURATION=59.993,SCTE35-OUT=0xFC002F0000000000FF0   00014056FFFFFF000E011622DCAFF000052636200000000000A0008029896F50   000008700000000   ... Media Segment declarations for 60s worth of media   #EXT-X-DATERANGE:ID="splice-6FFFFFF0",DURATION=59.993,SCTE35-IN=   0xFC002A0000000000FF00000F056FFFFFF000401162802E6100000000000A00   08029896F50000008700000000   ...9.  IANA Considerations   IANA has registered the following media type [RFC2046]:   Type name: application   Subtype name: vnd.apple.mpegurl   Required parameters: none   Optional parameters: none   Encoding considerations: encoded as UTF-8, which is 8-bit text.  This   media type may require encoding on transports not capable of handling   8-bit text.  SeeSection 4 for more information.   Security considerations: SeeSection 10.   Compression: this media type does not employ compression.Pantos & May                  Informational                    [Page 54]

RFC 8216                   HTTP Live Streaming               August 2017   Interoperability considerations: There are no byte-ordering issues,   since files are 8-bit text.  Applications could encounter   unrecognized tags, which SHOULD be ignored.   Published specification: seeSection 4.   Applications that use this media type: Multimedia applications such   as the iPhone media player in iOS 3.0 and later and QuickTime Player   in Mac OS X version 10.6 and later.   Fragment identifier considerations: no Fragment Identifiers are   defined for this media type.   Additional information:      Deprecated alias names for this type: none      Magic number(s): #EXTM3U      File extension(s): .m3u8, .m3u (seeSection 4)      Macintosh file type code(s): none   Person & email address to contact for further information: David   Singer, singer@apple.com.   Intended usage: LIMITED USE   Restrictions on usage: none   Author: Roger Pantos   Change Controller: David Singer10.  Security Considerations   Since the protocol generally uses HTTP to transfer data, most of the   same security considerations apply.  SeeSection 15 of HTTP   [RFC7230].   Media file parsers are typically subject to "fuzzing" attacks.   Implementors SHOULD pay particular attention to code that will parse   data received from a server and ensure that all possible inputs are   handled correctly.   Playlist files contain URIs, which clients will use to make network   requests of arbitrary entities.  Clients SHOULD range-check responses   to prevent buffer overflows.  See also the Security Considerations   section of "Uniform Resource Identifier (URI): Generic Syntax"   [RFC3986].Pantos & May                  Informational                    [Page 55]

RFC 8216                   HTTP Live Streaming               August 2017   Apart from URL resolution, this format does not employ any form of   active content.   Clients SHOULD limit each playback session to a reasonable number of   concurrent downloads (e.g., four) to avoid contributing to denial-of-   service attacks.   HTTP requests often include session state ("cookies"), which may   contain private user data.  Implementations MUST follow cookie   restriction and expiry rules specified by "HTTP State Management   Mechanism" [RFC6265] to protect themselves from attack.  See also the   Security Considerations section of that document, and "Use of HTTP   State Management" [RFC2964].   Encryption keys are specified by URI.  The delivery of these keys   SHOULD be secured by a mechanism such as HTTP Over TLS [RFC2818]   (formerly SSL) in conjunction with a secure realm or a session token.11.  References11.1.  Normative References   [AC_3]     Advanced Television Systems Committee, "Digital Audio              Compression (AC-3) (E-AC-3) Standard", ATSC              Standard A/52:2010, November 2010, <http://atsc.org/wp-content/uploads/2015/03/A52-201212-17.pdf>.   [AES_128]  National Institute of Standards and Technology, "Advanced              Encryption Standard (AES)", FIPS PUB 197,              DOI 10.6028/NIST.FIPS.197, November 2001,              <http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.197.pdf>.   [CEA608]   Consumer Electronics Association, "ANSI/CEA 608-E: Line 21              Data Services", April 2008.   [CEA708]   Consumer Technology Association, "Digital Television (DTV)              Closed Captioning", ANSI/CTA Standard CEA-708-E, August              2013, <https://standards.cta.tech/kwspub/published_docs/ANSI-CTA-708-E-Preview.pdf>.   [COMMON_ENC]              International Organization for Standardization,              "Information technology -- MPEG systems technologies --              Part 7: Common encryption in ISO base media file format              files", ISO/IEC 23001-7:2016, February 2016,              <http://www.iso.org/iso/catalogue_detail.htm?csnumber=68042>.Pantos & May                  Informational                    [Page 56]

RFC 8216                   HTTP Live Streaming               August 2017   [H_264]    International Telecommunications Union, "Advanced video              coding for generic audiovisual services", January 2012,              <http://www.itu.int/rec/T-REC-H.264>.   [HDCP]     Digital Content Protection LLC, "High-bandwidth Digital              Content Protection System - Mapping HDCP to HDMI",              February 2013, <http://www.digital-cp.com/sites/default/files/specifications/HDCP%20on%20HDMI%20Specification%20Rev2_2_Final1.pdf>.   [ISO_13818]              International Organization for Standardization, "Generic              coding of moving pictures and associated audio              information", ISO/IEC International Standard 13818,              October 2007,              <http://www.iso.org/iso/catalogue_detail?csnumber=44169>.   [ISO_13818_3]              International Organization for Standardization, "ISO/IEC              International Standard 13818-3:1998; Generic coding of              moving pictures and associated audio information - Part 3:              Audio", April 1998,              <http://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.htm?csnumber=26797>.   [ISO_13818_7]              International Organization for Standardization, "Generic              coding of moving pictures and associated audio information              - Part 7: Advanced Audio Coding (AAC)", ISO/IEC              International Standard 13818-3:2006, January 2006,              <http://www.iso.org/iso/home/store/catalogue_tc/catalogue_detail.htm?csnumber=43345>.   [ISO_14496]              International Organization for Standardization,              "Information technology -- Coding of audio-visual objects              -- Part 3: Audio", ISO/IEC 14496-3:2009, 2009,              <http://www.iso.org/iso/catalogue_detail?csnumber=53943>.   [ISO_8601] International Organization for Standardization, "Data              elements and interchange formats -- Information              interchange -- Representation of dates and times", ISO/IEC              International Standard 8601:2004, December 2004,              <http://www.iso.org/iso/catalogue_detail?csnumber=40874>.Pantos & May                  Informational                    [Page 57]

RFC 8216                   HTTP Live Streaming               August 2017   [ISOBMFF]  International Organization for Standardization,              "Information technology -- Coding of audio-visual objects              -- Part 12: ISO base media file format",              ISO/IEC 14496-12:2015, December 2015,              <http://www.iso.org/iso/catalogue_detail.htm?csnumber=68960>.   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail              Extensions (MIME) Part Two: Media Types",RFC 2046,              DOI 10.17487/RFC2046, November 1996,              <https://www.rfc-editor.org/info/rfc2046>.   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119,              DOI 10.17487/RFC2119, March 1997,              <https://www.rfc-editor.org/info/rfc2119>.   [RFC2818]  Rescorla, E., "HTTP Over TLS",RFC 2818,              DOI 10.17487/RFC2818, May 2000,              <https://www.rfc-editor.org/info/rfc2818>.   [RFC2964]  Moore, K. and N. Freed, "Use of HTTP State Management",BCP 44,RFC 2964, DOI 10.17487/RFC2964, October 2000,              <https://www.rfc-editor.org/info/rfc2964>.   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO              10646", STD 63,RFC 3629, DOI 10.17487/RFC3629, November              2003, <https://www.rfc-editor.org/info/rfc3629>.   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform              Resource Identifier (URI): Generic Syntax", STD 66,RFC 3986, DOI 10.17487/RFC3986, January 2005,              <https://www.rfc-editor.org/info/rfc3986>.   [RFC5646]  Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying              Languages",BCP 47,RFC 5646, DOI 10.17487/RFC5646,              September 2009, <https://www.rfc-editor.org/info/rfc5646>.   [RFC5652]  Housley, R., "Cryptographic Message Syntax (CMS)", STD 70,RFC 5652, DOI 10.17487/RFC5652, September 2009,              <https://www.rfc-editor.org/info/rfc5652>.   [RFC6265]  Barth, A., "HTTP State Management Mechanism",RFC 6265,              DOI 10.17487/RFC6265, April 2011,              <https://www.rfc-editor.org/info/rfc6265>.Pantos & May                  Informational                    [Page 58]

RFC 8216                   HTTP Live Streaming               August 2017   [RFC6381]  Gellens, R., Singer, D., and P. Frojdh, "The 'Codecs' and              'Profiles' Parameters for "Bucket" Media Types",RFC 6381,              DOI 10.17487/RFC6381, August 2011,              <https://www.rfc-editor.org/info/rfc6381>.   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data              Interchange Format",RFC 7159, DOI 10.17487/RFC7159, March              2014, <https://www.rfc-editor.org/info/rfc7159>.   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer              Protocol (HTTP/1.1): Message Syntax and Routing",RFC 7230, DOI 10.17487/RFC7230, June 2014,              <https://www.rfc-editor.org/info/rfc7230>.   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase inRFC2119 Key Words",BCP 14,RFC 8174, DOI 10.17487/RFC8174,              May 2017, <https://www.rfc-editor.org/info/rfc8174>.   [SCTE35]   Society of Cable Telecommunications Engineers, "Digital              Program Insertion Cueing Message for Cable", ANSI/SCTE 35,              August 2014, <http://www.scte.org/documents/pdf/Standards/ANSI_SCTE%2035%202014.pdf>.   [US_ASCII] American National Standard for Information Systems, "Coded              Character Sets - 7-Bit American National Standard Code for              Information Interchange (7-Bit ASCII)", ANSI X3.4,              December 1986.   [WebVTT]   World Wide Web Consortium (W3C), "WebVTT: The Web Video              Text Tracks Format", Draft Community Group Report, June              2017, <http://dev.w3.org/html5/webvtt/>.11.2.  Informative References   [CMAF]     International Organization for Standardization,              "Information technology -- Multimedia application format              (MPEG-A) -- Part 19: Common media application format              (CMAF) for segmented media", ISO/IEC FDIS 23000-19,              <https://www.iso.org/standard/71975.html>.   [ID3]      ID3.org, "The ID3 audio file data tagging format",              <http://www.id3.org/Developer_Information>.   [M3U]      Nullsoft, Inc., "The M3U Playlist format, originally              invented for the Winamp media player",              <https://en.wikipedia.org/w/index.php?title=M3U7amp;oldid=786631666>.Pantos & May                  Informational                    [Page 59]

RFC 8216                   HTTP Live Streaming               August 2017   [SampleEnc]              Apple Inc., "MPEG-2 Stream Encryption Format for HTTP Live              Streaming",              <https://developer.apple.com/library/ios/documentation/AudioVideo/Conceptual/HLS_Sample_Encryption/>.   [UNICODE]  The Unicode Consortium, "The Unicode Standard",              <http://www.unicode.org/versions/latest/>.   [UTI]      Apple Inc., "Uniform Type Identifier",              <http://developer.apple.com/library/ios/#documentation/general/conceptual/DevPedia-CocoaCore/UniformTypeIdentifier.html>.Contributors   Significant contributions to the design of this protocol were made by   Jim Batson, David Biderman, Bill May, Roger Pantos, Alan Tseng, and   Eryk Vershen.  Stuart Cheshire helped edit the specification.Authors' Addresses   Roger Pantos (editor)   Apple, Inc.   Cupertino, California   United States of America   Email: http-live-streaming-review@group.apple.com   William May, Jr.   Major League Baseball Advanced Media   New York, New York   United States of America   Email: bill.may@mlb.comPantos & May                  Informational                    [Page 60]