Avid DNxHD ("DigitalNonlinear ExtensibleHighDefinition") is alossyhigh-definition videopost-productioncodec developed byAvid for multi-generationcompositing with reduced storage and bandwidth requirements. It is an implementation ofSMPTE VC-3 standard.[1]
DNxHD is a video codec intended to be usable as both an intermediate format suitable for use while editing and as a presentation format. DNxHD data is typically stored in anMXF container, although it can also be stored in aQuickTime container.
On February 13, 2008, Avid reported that DNxHD was approved as compliant with the SMPTE VC-3 standard.[2]
DNxHD is intended to be an open standard, but as of March 2008, has remained effectively a proprietary Avid format. The source code for the Avid DNxHD codec is freely available from Avid for internal evaluation and review, although commercial use requires Avid licensing approval. It has been commercially licensed to a number of companies including Ikegami, FilmLight,Harris Corporation,JVC, Seachange,EVS Broadcast Equipment.[3]
On September 14, 2014, at the Avid Connect event inAmsterdam,Netherlands, Avid announced theDNxHR codec to support resolutions greater than1080p, such as2K and4K.[4]
On December 22, 2014, Avid Technology released an update forMedia Composer that added support for 4K resolution, theRec. 2020 color space, and a bit rate of up to 3,730 Mbit/s with the DNxHR codec.[5][6]
DNxHD was first supported inAvid DS Nitris (Sept 2004), thenAvid Media Composer Adrenaline with the DNxcel option (Dec 2004) and finally byAvid Symphony Nitris (Dec 2005).Xpress Pro is limited to using DNxHD 8-bit compression, which is either imported from file or captured using a Media Composer with Adrenaline hardware. Media Composer 2.5 also allows editing of fully uncompressed HD material that was either imported or captured on a Symphony Nitris or DS Nitris system. Ikegami'sEditcam camera system is unique in its support for DNxHD, and records directly to DNxHD encoded video. Such material is immediately accessible by editing platforms that directly support the DNxHD codec. TheArri Alexasupports DNxHD since November 2011.Blackmagic Design HyperDeck Shuttle 2 and HyperDeck Studio support DNxHD as of 2012.[7]AJA Video Systems has supported the DNxHD codec in its Ki Pro Mini and Ki Pro Rack recorders and players since 2012.
A standalone QuickTime codec for bothWindows XP andMac OS X is available to create and play QuickTime files containing DNxHD material.
Since September 2007, theopen sourceFFmpeg project is providing 8-bit VC-3/DNxHD encoding and decoding features thanks to BBC Research who sponsored the project and Baptiste Coudurier who implemented it. In July 2011, FFmpeg added 10-bit encoding support.[8] DNxHD support is included in stable version 0.5 of FFmpeg, released on March 10, 2009.[9][10] This allowsLinuxnon-linear video editorsCinelerra andKdenlive to use DNxHD.
At the April 2012NAB show, Brevity introduced a customized algorithm for the accelerated transport and encoding of DNxHD files.[11]
DNxHD is very similar toJPEG. Every frame is independent and consists ofVLC-codedDCT coefficients.
The header consists of many parts and may include quantization tables and 2048 bits of user data. Each frame also has twoGUIDs and timestamp. The frame header is packed into big-endiandwords. Actual frame data consists of packedmacroblocks using a technique almost identical toJPEG: DC prediction and variable-length codes with run length encoding for other 63 coefficients.DC coefficient is not quantized.
The codec supports alpha channel information.
The DNxHD codec was submitted to the SMPTE organization as the framework for the VC-3 family of standards. It was approved as SMPTE VC-3 after a two-year testing and validation process in 2008 and 2009:[1][2][12][13]