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Network Working Group                                          L. GharaiRequest for Comments: 4175                                       USC/ISICategory: Standards Track                                     C. Perkins                                                   University of Glasgow                                                          September 2005RTP Payload Format for Uncompressed VideoStatus of This Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2005).Abstract   This memo specifies a packetization scheme for encapsulating   uncompressed video into a payload format for the Real-time Transport   Protocol, RTP.  It supports a range of standard- and high-definition   video formats, including common television formats such as ITU   BT.601, and standards from the Society of Motion Picture and   Television Engineers (SMPTE), such as SMPTE 274M and SMPTE 296M.  The   format is designed to be applicable and extensible to new video   formats as they are developed.1.  Introduction   This memo defines a scheme to packetize uncompressed, studio-quality   video streams for transport using RTP [RTP].  It supports a range of   standard and high-definition video formats, including ITU-R BT.601   [601], SMPTE 274M [274] and SMPTE 296M [296].   Formats for uncompressed standard definition television are defined   by ITU Recommendation BT.601 [601] along with bit-serial and parallel   interfaces in Recommendation BT.656 [656].  These formats allow both   625-line and 525-line operation, with 720 samples per digital active   line, 4:2:2 color sub-sampling, and 8- or 10-bit digital   representation.Gharai & Perkins            Standards Track                     [Page 1]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005   The representation of uncompressed high-definition television is   specified in SMPTE standards 274M [274] and 296M [296].  SMPTE 274M   defines a family of scanning systems with an image format of   1920x1080 pixels with progressive and interlaced scanning, while   SMPTE 296M defines systems with an image size of 1280x720 pixels and   progressive scanning.  In progressive scanning, scan lines are   displayed in sequence from top to bottom of a full frame.  In   interlaced scanning, a frame is divided into its odd and even scan   lines (called fields) and the two fields are displayed in succession.   SMPTE 274M and 296M define images with aspect ratios of 16:9, and   define the digital representation for RGB and YCbCr components.  In   the case of YCbCr components, the Cb and Cr components are   horizontally sub-sampled by a factor of two (4:2:2 color encoding).   Although these formats differ in their details, they are structurally   very similar.  This memo specifies a payload format to encapsulate   these and other similar video formats for transport within RTP.2.  Conventions Used in This Document   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described inRFC 2119 [2119].3.  Payload Design   Each scan line of digital video is packetized into one or more RTP   packets.  If the data for a complete scan line exceeds the network   MTU, the scan line SHOULD be fragmented into multiple RTP packets,   each smaller than the MTU.  A single RTP packet MAY contain data for   more than one scan line.  Only the active samples are included in the   RTP payload: inactive samples and the contents of horizontal and   vertical blanking SHOULD NOT be transported.  In instances where   ancillary data is being transmitted, the sender and receiver can   disambiguate between ancillary and video data via scan line numbers.   That is, the ancillary data will use scan line numbers that are not   within the scope of the video frame.   Scan line numbers are included in the RTP payload header, along with   a field identifier for interlaced video.      For SMPTE 296M format video, valid scan line numbers are from 26      through 745, inclusive.  For progressive scan SMPTE 274M format      video, valid scan lines are from scan line 42 through 1121,      inclusive.  For interlaced scan SMPTE 274M format video, valid      scan line numbers for field one (F=0) are from 21 to 560 and valid      scan line numbers for the second field (F=1) are from 584 to 1123.      For ITU-R BT.601 format video, the blanking intervals defined inGharai & Perkins            Standards Track                     [Page 2]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005      BT.656 are used: for 625 line video, lines 24 to 310 of field one      (F=0) and 337 to 623 of the second field (F=1) are valid; for 525      line video, lines 21 to 263 of the first field, and 284 to 525 of      the second field are valid.  Other formats (e.g., [372]) may      define different ranges of active lines.   The payload header contains a 16-bit extension to the standard 16-bit   RTP sequence number, thereby extending the sequence number to 32 bits   and enabling the payload format to accommodate high data rates   without ambiguity.  This is necessary as the 16-bit RTP sequence   number will roll over very quickly for high data rates.  For example,   for a 1-Gbps video stream with packet sizes of at least 1000 octets,   the standard RTP packet will roll over in 0.5 seconds, which can be a   problem for detecting loss and out-of-order packets particularly in   instances where the round-trip time is greater than half a second.   The extended 32-bit number allows for a longer wrap-around time of   approximately nine hours.   Each scan line comprises an integer number of pixels.  Each pixel is   represented by a number of samples.  Samples may be coded as 8-, 10-,   12-, or 16-bit values.  A sample may represent a color component or a   luminance component of the video.  Color samples may be shared   between adjacent pixels.  The sharing of color samples between   adjacent pixels is known as color sub-sampling.  This is typically   done in the YCbCr color space for the purpose of reducing the size of   the image data.   Pixels that share sample values MUST be transported together as a   "pixel group".  If 10-bit or 12-bit samples are used, each pixel may   also comprise a non-integer number of octets.  In this case, several   pixels MUST be combined into an octet-aligned pixel group for   transmission.  These restrictions simplify the operation of receivers   by ensuring that the complete payload is octet aligned, and that   samples relating to a single pixel are not fragmented across multiple   packets [ALF].   For example, in YCbCr video with 4:1:1 color sub-sampling, each group   of 4 adjacent pixels comprises 6 samples, Y1 Y2 Y3 Y4 Cr Cb, with the   Cr and Cb values being shared between all 4 pixels.  If samples are   8-bit values, the result is a group of 4 pixels comprising 6 octets.   If, however, samples are 10-bit values, the resulting 60-bit group is   not octet aligned.  To be both octet aligned and appropriately   framed, two groups of 4 adjacent pixels must be collected, thereby   becoming octet aligned on a 15-octet boundary.  This length is   referred to as the pixel group size ("pgroup").Gharai & Perkins            Standards Track                     [Page 3]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005   Formally, the "pgroup" parameter is the size in octets of the   smallest grouping of pixels such that 1) the grouping comprises an   integer number of octets; and 2) if color sub-sampling is used,   samples are only shared within the grouping.  When packetizing   digital active line content, video data MUST NOT be fragmented within   a pgroup.   Video content is almost always associated with additional information   such as audio tracks, time code, etc.  In professional digital video   applications, this data is commonly embedded in non-active portions   of the video stream (horizontal and vertical blanking periods) so   that precise and robust synchronization is maintained.  This payload   format requires that applications using such synchronized ancillary   data SHOULD deliver it in separate RTP sessions that operate   concurrently with the video session.  The normal RTP mechanisms   SHOULD be used to synchronize the media.4.  RTP Packetization   The standard RTP header is followed by a 2-octet payload header that   extends the RTP Sequence Number, and by a 6-octet payload header for   each line (or partial line) of video included.  One or more lines, or   partial lines, of video data follow.  This format makes the payload   header 32-bit aligned in the common case, where one scan line (or   fragment) of video is included in each RTP packet.   For example, if two lines of video are encapsulated, the payload   format will be as shown in Figure 1.Gharai & Perkins            Standards Track                     [Page 4]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005       0                   1                   2                   3       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      | V |P|X|   CC  |M|    PT       |       Sequence Number         |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                           Time Stamp                          |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |                             SSRC                              |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |   Extended Sequence Number    |            Length             |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |F|          Line No            |C|           Offset            |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |            Length             |F|          Line No            |      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+      |C|           Offset            |                               .      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               .      .                                                               .      .                 Two (partial) lines of video data             .      .                                                               .      +---------------------------------------------------------------+     Figure 1: RTP Payload Format showing two (partial) lines of video4.1.  The RTP Header   The fields of the fixed RTP header have their usual meaning, with the   following additional notes:   Payload Type (PT): 7 bits     A dynamically allocated payload type field that designates the     payload as uncompressed video.   Timestamp: 32 bits     For progressive scan video, the timestamp denotes the sampling     instant of the frame to which the RTP packet belongs.  Packets MUST     NOT include data from multiple frames, and all packets belonging to     the same frame MUST have the same timestamp.     For interlaced video, the timestamp denotes the sampling instant of     the field to which the RTP packet belongs.  Packets MUST NOT     include data from multiple fields, and all packets belonging to the     same field MUST have the same timestamp.  Use of field timestamps,     rather than a frame timestamp and field indicator bit, is needed to     support reverse 3-2 pulldown.Gharai & Perkins            Standards Track                     [Page 5]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005     A 90-kHz timestamp SHOULD be used in both cases.  If the sampling     instant does not correspond to an integer value of the clock (as     may be the case when interleaving), the value SHALL be truncated to     the next lowest integer, with no ambiguity.   Marker bit (M): 1 bit     If progressive scan video is being transmitted, the marker bit     denotes the end of a video frame.  If interlaced video is being     transmitted, it denotes the end of the field.  The marker bit MUST     be set to 1 for the last packet of the video frame/field.  It MUST     be set to 0 for other packets.   Sequence Number: 16 bits     The low-order bits for RTP sequence number.  The standard 16-bit     sequence number is augmented with another 16 bits in the payload     header in order avoid problems due to wrap-around when operating at     high rate rates.4.2.  Payload Header   Extended Sequence Number: 16 bits     The high order bits of the extended 32-bit sequence number, in     network byte order.   Length: 16 bits     Number of octets of data included from this scan line, in network     byte order.  This MUST be a multiple of the pgroup value.   Line No.: 15 bits     Scan line number of encapsulated data, in network byte order.     Successive RTP packets MAY contains parts of the same scan line     (with an incremented RTP sequence number, but the same timestamp),     if it is necessary to fragment a line.   Offset: 15 bits     Offset of the first pixel of the payload data within the scan line.     If YCbCr format data is being transported, this is the pixel offset     of the luminance sample; if RGB format data is being transported,     it is the pixel offset of the red sample; if BGR format data is     being transported, it is the pixel offset of the blue sample.  TheGharai & Perkins            Standards Track                     [Page 6]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005     value is in network byte order.  The offset has a value of zero if     the first sample in the payload corresponds to the start of the     line, and increments by one for each pixel.   Field Identification (F): 1 bit     Identifies which field the scan line belongs to, for interlaced     data.  F=0 identifies the first field and F=1 the second field.     For progressive scan data (e.g., SMPTE 296M format video), F MUST     always be set to zero.   Continuation (C): 1 bit     Determines if an additional scan line header follows the current     scan line header in the RTP packet.  Set to 1 if an additional     header follows, implying that the RTP packet is carrying data for     more than one scan line.  Set to 0 otherwise.  Several scan lines     MAY be included in a single packet, up to the path MTU limit.  The     only way to determine the number of scan lines included per packet     is to parse the payload headers.4.3.  Payload Data   Depending on the video format, each RTP packet can include either a   single complete scan line, a single fragment of a scan line, or one   (or more) complete scan lines and scan line fragments.  The length of   each scan line or scan line fragment MUST be an integer multiple of   the pgroup size in octets.  Scan lines SHOULD be fragmented so that   the resulting RTP packet is smaller than the path MTU.   It is possible that the scan line length is not evenly divisible by   the number of pixels in a pgroup, so the final pixel data of a scan   line does not align to either an octet or a pgroup boundary.   Nonetheless, the payload MUST contain a whole number of pgroups; the   sender MUST fill the remaining bits of the final pgroup with zero and   the receiver MUST ignore the fill data. (In effect, the trailing edge   of the image is black-filled to a pgroup boundary.)   For RGB format video, samples are packed in order Red-Green-Blue.   For BGR format video, samples are packed in order Blue-Green-Red.   For both formats, if 8-bit samples are used, the pgroup is 3 octets.   If 10-bit samples are used, samples from 4 adjacent pixels form 15-   octet pgroups.  If 12-bit samples are used, samples from 2 adjacent   pixels form 9-octet pgroups.  If 16-bit samples are used, each pixel   forms a separate 6-octet pgroup.Gharai & Perkins            Standards Track                     [Page 7]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005   For RGBA format video, samples are packed in order Red-Green-Blue-   Alpha.  For BGRA format video, samples are packed in order Blue-   Green-Red-Alpha.  For 8-, 10-, 12-, or 16-bit samples, each pixel   forms its own pgroup, with octet sizes of 4, 5, 6, and 8,   respectively.   If the video is in YCbCr format, the packing of samples into the   payload depends on the color sub-sampling used.   For YCbCr 4:4:4 format video, samples are packed in order Cb-Y-Cr for   both interlaced and progressive frames.  If 8-bit samples are used,   the pgroup is 3 octets.  If 10-bit samples are used, samples from 4   adjacent pixels form 15-octet pgroups.  If 12-bit samples are used,   samples from 2 adjacent pixels form 9-octet pgroups.  If 16-bit   samples are used, each pixel forms a separate 6-octet pgroup.   For YCbCr 4:2:2 format video, the Cb and Cr components are   horizontally sub-sampled by a factor of two (each Cb and Cr sample   corresponds to two Y components).  Samples are packed in order Cb0-   Y0-Cr0-Y1 for both interlaced and progressive scan lines.  For 8-,   10-, 12-, or 16-bit samples, the pgroup is formed from two adjacent   pixels (4, 5, 6, or 8 octets, respectively).   For YCbCr 4:1:1 format video, the Cb and Cr components are   horizontally sub-sampled by a factor of four (each Cb and Cr sample   corresponds to four Y components).  Samples are packed in order Cb0-   Y0-Y1-Cr0-Y2-Y3 for both interlaced and progressive scan lines.  For   8-, 10-, 12-, or 16-bit samples, the pgroup is formed from four   adjacent pixels (6, 15, 9, or 12 octets, respectively).   For YCbCr 4:2:0 video, the Cb and Cr components are sub-sampled by a   factor of two both horizontally and vertically.  Therefore,   chrominance samples are shared between certain adjacent lines.   Figure 2 shows the composition of luminance and chrominance samples   for a 6x6 pixel grid of 4:2:0 YCbCr video.  The pixel group is a   group of four pixels arranged in a 2x2 matrix.  The octet size of the   pgroup for progressive scan 4:2:0 video with samples sizes of 8, 10,   12, and 16 bits is 6, 15, 9, and 12 octets, respectively.  For   interlaced 4:2:0 video, the corresponding pgroups are 4, 5, 6, and 8   octets.Gharai & Perkins            Standards Track                     [Page 8]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005       line 0:  Y00   Y01   Y02   Y03   Y04   Y05                Cb00 Cr00   Cb01 Cr01   Cb02 Cr02       line 1:  Y10   Y11   Y12   Y13   Y14   Y15       line 2:  Y20   Y21   Y22   Y23   Y24   Y25                Cb10 Cr10   Cb11 Cr11   Cb12 Cr12       line 3:  Y30   Y31   Y32   Y33   Y34   Y35       line 4:  Y40   Y41   Y42   Y43   Y44   Y45                Cb20 Cr20   Cb21 Cr21   Cb22 Cr22       line 5:  Y50   Y51   Y52   Y53   Y54   Y55     Figure 2: Chrominance/luminance composition in 4:2:0 YCbCr video   When packetizing progressive scan 4:2:0 YCbCr video, samples from two   consecutive scan lines are included in each packet.  The scan line   number in the payload header is set to that of the first scan line of   the pair:     line 0/1:     Y00-Y01-Y10-Y11-Cb00-Cr00 Y02-Y03-Y12-Y13-Cb01-Cr01                                           Y04-Y05-Y14-Y15-Cb02-Cr02     line 2/3:     Y20-Y21-Y30-Y31-Cb10-Cr10 Y22-Y23-Y32-Y33-Cb11-Cr11                                           Y24-Y25-Y34-Y35-Cb12-Cr12     line 4/5:     Y40-Y41-Y50-Y51-Cb20-Cr20 Y42-Y43-Y52-Y53-Cb21-Cr21                                           Y44-Y45-Y54-Y55-Cb22-Cr22     Figure 3: Packetization of progressive 4:2:0 YCbCr video   For interlaced transport, chrominance samples are transported with   every other line.  The first set of chrominance samples may be   transported with either the first line of field 0, or the first line   of field 1.  Figure 4 illustrates the transport of chrominance   samples starting with the first line of field 0 (signaled by the   "top-field-first" MIME parameter).Gharai & Perkins            Standards Track                     [Page 9]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005     field 0:        line 0: Y00-Y01-Cb00-Cr00 Y02-Y03-Cb01-Cr01 Y04-Y05-Cb02-Cr02        line 2: Y20-Y21 Y22-Y23 Y24-Y25        line 4: Y40-Y41-Cb20-Cr20 Y42-Y43-Cb21-Cr21 Y44-Y45-Cb22-Cr22     field 1:        line 1: Y10-Y11 Y12-Y13 Y14-Y15        line 3: Y30-Y31-Cb10-Cr10 Y32-Y33-Cb11 Cr11 Y34-Y35-Cb12-Cr12        line 5: Y50-Y51 Y52-Y53 Y54-Y55     Figure 4: Packetization of interlaced 4:2:0 YCbCr video with               top-field-first.   Chrominance values may be sampled with different offsets relative to   luminance values.  For instance, in Figure 2, chrominance values are   sampled at the same distance from neighboring luminance samples.  It   is also possible for a chrominance sample to be co-sited with a   luminance sample, as in Figure 5:       line 0:  Y00-C   Y01   Y02-C   Y03   Y04-C   Y05       line 1:  Y10     Y11   Y12     Y13   Y14     Y15       line 2:  Y20-C   Y21   Y22-C   Y23   Y24-C   Y25       line 3:  Y30     Y31   Y32     Y33   Y34     Y35       line 4:  Y40-C   Y41   Y42-C   Y43   Y44-C   Y45       line 5:  Y50     Y51   Y52     Y53   Y54     Y55     Figure 5: Co-sited video sampling in 4:2:0 YCbCr video where C               designates a CbCr pair   In general, chrominance values may be placed between luminance   samples or co-sited.  Positions can be designated by an integer   numbering system starting from left to right and top to bottom.  The   position matrices shown in Figures 6, 7, and 8 apply for 4:2:0,   4:2:2, and 4:1:1 video, respectively:       line N:    Y[0] [1] Y[2]   Y[0] [1] Y[2]                   [3] [4] Y[5]    [3] [4]  [5]       line N+1:  Y[6] [7] Y[8]   Y[6] [7] Y[8]     Figure 6: Chrominance position matrix for 4:2:0 YCbCr videoGharai & Perkins            Standards Track                    [Page 10]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005       line N:    Y[0] [1] Y[2] [3]  Y[0] [1] Y[2] [3]       line N+1:  Y[0] [1] Y[2] [3]  Y[0] [1] Y[2] [3]     Figure 7: Chrominance position matrix for 4:2:2 YCbCr video       line N:    Y[0] [1] Y[2] [3] Y[4] [5] Y[6]       line N+1:  Y[0] [1] Y[2] [3] Y[4] [5] Y[6]     Figure 8: Chrominance position matrix for 4:1:1 YCbCr video   Although these positions do not affect the packetization order of   chrominance and luminance samples, the information is needed for   interpolation prior to display and therefore should be signaled to   the receiver.5.  RTCP Considerations   RTCP SHOULD be used as specified inRFC 3550 [RTP].  It is to be   noted that the sender's octet count in SR packets and the cumulative   number of packets lost will wrap around quickly for high data rate   streams.  This means that these two fields may not accurately   represent octet count and number of packets lost since the beginning   of transmission, as defined inRFC 3550.  Therefore, for network   monitoring purposes, other means of keeping track of these variables   SHOULD be used.6.  IANA Considerations   The IANA has registered one new MIME subtype along with an associated   RTP Payload Format, and has created two sub-parameter registries, as   described in the following.6.1.  MIME type registration   MIME media type name: video   MIME subtype name: raw   Required parameters:     rate: The RTP timestamp clock rate.  Applications using this     payload format SHOULD use a value of 90000.     sampling: Determines the color (sub-)sampling mode of the video     stream.  Currently defined values are RGB, RGBA, BGR, BGRA,     YCbCr-4:4:4, YCbCr-4:2:2, YCbCr-4:2:0, and YCbCr-4:1:1.  New values     may be registered as described insection 6.2 of RFC 4175.Gharai & Perkins            Standards Track                    [Page 11]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005     width: Determines the number of pixels per line.  This is an     integer between 1 and 32767.     height: Determines the number of lines per frame.  This is an     integer between 1 and 32767.     depth: Determines the number of bits per sample.  This is an     integer with typical values including 8, 10, 12, and 16.     colorimetry: This parameter defines the set of colorimetric     specifications and other transfer characteristics for the video     source, by reference to an external specification.  Valid values     and their specification are:          BT601-5      ITU Recommendation BT.601-5 [601]          BT709-2      ITU Recommendation BT.709-2 [709]          SMPTE240M    SMPTE standard 240M [240]     New values may be registered as described in section 6.2 ofRFC4175.   Optional parameters:     Interlace: If this OPTIONAL parameter is present, it indicates that     the video stream is interlaced.  If absent, progressive scan is     implied.     Top-field-first: If this OPTIONAL parameter is present, it     indicates that chrominance samples are packetized starting with the     first line of field 0.  Its absence implies that chrominance     samples are packetized starting with the first line of field 1.     chroma-position: This OPTIONAL parameter defines the position of     chrominance samples relative to luminance samples.  It is either a     single integer or a comma separated pair of integers.  Integer     values range from 0 to 8, as specified in Figures 6-8 ofRFC 4175.     A single integer implies that Cb and Cr are co-sited.  A comma     separated pair of integers designates the locations of Cb and Cr     samples, respectively.  In its absence, a single value of zero is     assumed for color-subsampled video (chroma-position=0).     gamma: An OPTIONAL floating point gamma correction value.Gharai & Perkins            Standards Track                    [Page 12]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005   Encoding considerations:     Uncompressed video is only transmitted over RTP as specified inRFC4175.  No file format media type has been defined to go with this     transmission media type at this time.   Security considerations: Seesection 9 of RFC 4175.   Interoperability considerations: NONE.   Published specification:RFC 4175.   Applications which use this media type: Video communication.   Additional information: None   Person & email address to contact for further information:     Ladan Gharai <ladan@isi.edu>     IETF Audio/Video Transport working group.   Intended usage: COMMON   Author: Ladan Gharai <ladan@isi.edu>   Change controller: IETF AVT Working Group         delegated from the IESG6.2.  Parameter Registration   New values of the "sampling" parameter MAY be registered with the   IANA provided they reference an RFC or other permanent and readily   available specification (the Specification Required policy ofRFC2434 [2434]).  A new registration MUST define the packing order of   samples and a valid combinations of color and sub-sampling modes.   New values of the "colorimetry" parameter MAY be registered with the   IANA provided they reference an RFC or other permanent and readily   available specification if colorimetric parameters and other   applicable transfer characteristics (the Specification Required   policy ofRFC 2434 [2434]).7.  Mapping MIME Parameters into SDP   The information carried in the MIME media type specification has a   specific mapping to fields in the Session Description Protocol (SDP)   [SDP], which is commonly used to describe RTP sessions.  When SDP is   used to specify sessions transporting uncompressed video, the mapping   is as follows:Gharai & Perkins            Standards Track                    [Page 13]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005   -  The MIME type ("video") goes in SDP "m=" as the media name.   -  The MIME subtype (payload format name) goes in SDP "a=rtpmap" as      the encoding name.   -  Remaining parameters go in the SDP "a=fmtp" attribute by copying      them directly from the MIME media type string as a semicolon-      separated list of parameter=value pairs.   A sample SDP mapping for uncompressed video is as follows:     m=video 30000 RTP/AVP 112     a=rtpmap:112 raw/90000     a=fmtp:112 sampling=YCbCr-4:2:2; width=1280; height=720; depth=10;                              colorimetry=BT.709-2; chroma-position=1   In this example, a dynamic payload type 112 is used for uncompressed   video.  The RTP sampling clock is 90 kHz.  Note that the "a=fmtp:"   line has been wrapped to fit this page, and will be a single long   line in the SDP file.8.  Security Considerations   RTP packets using the payload format defined in this specification   are subject to the security considerations discussed in the RTP   specification [RTP] and any appropriate RTP profile.  This implies   that confidentiality of the media streams is achieved by encryption.   This payload type does not exhibit any significant non-uniformity in   the receiver side computational complexity for packet processing to   cause a potential denial-of-service threat.   It is important to note that uncompressed video can have immense   bandwidth requirements (up to 270 Mbps for standard-definition video,   and approximately 1 Gbps for high-definition video).  This is   sufficient to cause potential for denial-of-service if transmitted   onto most currently available Internet paths.   Accordingly, if best-effort service is being used, users of this   payload format MUST monitor packet loss to ensure that the packet   loss rate is within acceptable parameters.  Packet loss is considered   acceptable if a TCP flow across the same network path, and   experiencing the same network conditions, would achieve an average   throughput, measured on a reasonable timescale, that is not less than   the RTP flow is achieving.  This condition can be satisfied by   implementing congestion control mechanisms to adapt the transmissionGharai & Perkins            Standards Track                    [Page 14]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005   rate (or the number of layers subscribed for a layered multicast   session), or by arranging for a receiver to leave the session if the   loss rate is unacceptably high.   This payload format may also be used in networks that provide   quality-of-service guarantees.  If enhanced service is being used,   receivers SHOULD monitor packet loss to ensure that the service that   was requested is actually being delivered.  If it is not, then they   SHOULD assume that they are receiving best-effort service and behave   accordingly.9.  Relation toRFC 2431   In comparison withRFC 2431, this memo specifies support for a wider   variety of uncompressed video, in terms of frame size, color sub-   sampling and sample sizes.  Although [BT656] can transport up to 4096   scan lines and 2048 pixels per line, our payload type can support up   to 32768 scan lines and pixels per line.  Also,RFC 2431 only address   4:2:2 YCbCr data, while this memo covers YCbCr, RGB, RGBA, BGR, BGRA,   and most common color sub-sampling schemes.  Given the variety of   video types that we cover, this memo also assumes out-of-band   signaling for sample size and data types (RFC 2431 uses in band   signaling).10.  Relation toRFC 3497RFC 3497 [292RTP] specifies a RTP payload format for encapsulating   SMPTE 292M video.  The SMPTE 292M standard defines a bit-serial   digital interface for local area High-Definition Television (HDTV)   transport.  As a transport medium, SMPTE 292M utilizes 10-bit words   and a fixed 1.485 Gbps (and 1.485/1.001 Gbps) data rate.  SMPTE 292M   is typically used in the broadcast industry for the transport of   other video formats such as SMPTE 260M, SMPTE 295M, SMPTE 274M, and   SMPTE 296M.RFC 3497 defines a circuit emulation for the transport of SMPTE 292M   over RTP.  It is very specific to SMPTE 292 and has been designed to   be interoperable with existing broadcast equipment with a constant   rate of 1.485 Gbps.   This memo defines a flexible native packetization scheme that can   packetize any uncompressed video, at varying data rates.  In   addition, unlikeRFC 3497, this memo only transports active video   pixels (i.e., horizontal and vertical blanking are not transported).Gharai & Perkins            Standards Track                    [Page 15]

RFC 4175       RTP Payload Format for Uncompressed Video  September 200511.  Acknowledgements   The authors are grateful to Philippe Gentric, Chuck Harrison, Stephan   Wenger, and Dave Singer for their feedback.   This memo is based upon work supported by the U.S. National Science   Foundation (NSF) under Grant No. 0230738.  Any opinions, findings,   and conclusions or recommendations expressed in this material are   those of the authors and do not necessarily reflect the views of NSF.Normative References   [RTP]    Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,            "RTP: A Transport Protocol for Real-Time Applications", STD            64,RFC 3550, July 2003.   [2119]   Bradner, S., "Key words for use in RFCs to Indicate            Requirement Levels",BCP 14,RFC 2119, March 1997.   [2434]   Narten, T. and H. Alvestrand, "Guidelines for Writing an            IANA Considerations Section in RFCs",BCP 26,RFC 2434,            October 1998.   [601]    International Telecommunication Union, "Studio encoding            parameters of digital television for standard 4:3 and wide            screen 16:9 aspect ratios", Recommendation BT.601, October            1995.   [709]    International Telecommunication Union, "Parameter Values for            HDTV Standards for Production and International Programme            Exchange", Recommendation BT.709-2   [240]    Society of Motion Picture and Television Engineers,            "Television - Signal Parameters - 1125-Line High-Definition            Production", SMPTE 240M-1999.Informative References   [274]    Society of Motion Picture and Television Engineers,            "1920x1080 Scanning and Analog and Parallel Digital            Interfaces for Multiple Picture Rates", SMPTE 274M-1998.   [296]    Society of Motion Picture and Television Engineers,            "1280x720 Scanning, Analog and Digital Representation and            Analog Interfaces", SMPTE 296M-1998.Gharai & Perkins            Standards Track                    [Page 16]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005   [372]    Society of Motion Picture and Television Engineers, "Dual            Link 292M Interface for 1920 x 1080 Picture Raster", SMPTE            372M-2002.   [ALF]    Clark, D. D., and Tennenhouse, D. L., "Architectural            Considerations for a New Generation of Protocols", In            Proceedings of SIGCOMM '90 (Philadelphia, PA, Sept. 1990),            ACM.   [SDP]    Handley, M. and V. Jacobson, "SDP: Session Description            Protocol",RFC 2327, April 1998.   [BT656]  Tynan, D., "RTP Payload Format for BT.656 Video Encoding",RFC 2431, October 1998.   [292RTP] Gharai, L., Perkins, C., Goncher, G., and A. Mankin, "RTP            Payload Format for Society of Motion Picture and Television            Engineers (SMPTE) 292M Video",RFC 3497, March 2003.   [656]    International Telecommunication Union, "Interfaces for            Digital Component Video Signals in 525-line and 625-line            Television Systems Operating at the 4:2:2 Level of            Recommendation ITU-R BT.601 (Part A)", Recommendation            BT.656, April 1998.Authors' Addresses   Ladan Gharai   USC Information Sciences Institute   3811 N. Fairfax Drive, #200   Arlington, VA 22203   USA   EMail: ladan@isi.edu   Colin Perkins   University of Glasgow   Department of Computing Science   17 Lilybank Gardens   Glasgow G12 8QQ   United Kingdom   EMail: csp@csperkins.orgGharai & Perkins            Standards Track                    [Page 17]

RFC 4175       RTP Payload Format for Uncompressed Video  September 2005Full Copyright Statement   Copyright (C) The Internet Society (2005).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at ietf-   ipr@ietf.org.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Gharai & Perkins            Standards Track                    [Page 18]