DNxHD codec
Encyclopedia
Avid DNxHD, which stands for "Digital Nonlinear Extensible High Definition", is a lossy high-definition video
post-production
codec
engineered for multi-generation compositing
with reduced storage and bandwidth requirements. It is an implementation of SMPTE VC-3 standard. DNxHD codec was developed by Avid Technology
, Inc.
of 8 bits.
DNxHD data is typically stored in an MXF
container, although it can also be stored in a Quicktime
container.
On February 13, 2008 Avid reported that DNxHD was approved as compliant with the SMPTE VC3 standard.
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 and EVS Broadcast Equipment
.
(Sept 2004), then Avid Media Composer Adrenaline with the DNxcel option (Dec 2004) and finally by Avid 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's Editcam
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.
A standalone Quicktime codec for both Windows XP
and Mac OS X
is available to create and play Quicktime files containing DNxHD material.
Since September 2007 the open source
FFmpeg
project is providing 8-bit (but not 10-bit) VC-3/DNxHD encoding and decoding features thanks to BBC Research who sponsored the project and Baptiste Coudurier who implemented it. It is included in stable version 0.5 of FFmpeg, released on March 10, 2009. (ffmpeg -i -vcodec dnxhd -b -an output.mov). This allows Linux
non-linear video editors Cinelerra
and Kdenlive
to use DNxHD.
. Every frame is independent and consists of VLC-coded DCT
coefficients.
Header consists of many parts and may include quantization tables and 2048 bits of user data. Also each frame has two GUIDs and timestamp. The frame header is packed into big-endian dwords. Actual frame data consists of packed macroblocks using a technique almost identical to JPEG
: 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.
High-definition video
High-definition video or HD video refers to any video system of higher resolution than standard-definition video, and most commonly involves display resolutions of 1,280×720 pixels or 1,920×1,080 pixels...
post-production
Post-production
Post-production is part of filmmaking and the video production process. It occurs in the making of motion pictures, television programs, radio programs, advertising, audio recordings, photography, and digital art...
codec
Codec
A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...
engineered for multi-generation compositing
Compositing
Compositing is the combining of visual elements from separate sources into single images, often to create the illusion that all those elements are parts of the same scene. Live-action shooting for compositing is variously called "chroma key", "blue screen", "green screen" and other names. Today,...
with reduced storage and bandwidth requirements. It is an implementation of SMPTE VC-3 standard. DNxHD codec was developed by Avid Technology
Avid Technology
Avid Technology, Inc. is an American company specializing in video and audio production technology; specifically, digital non-linear editing systems, management and distribution services. It was created in 1987 and became a publicly traded company in 1993...
, Inc.
Overview
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 offers a choice of three user-selectable bit rates: 220 Mbit/s with a bit depth of 10 or 8 bits, and 145 or 36 Mbit/s with a bit depthBit depth
Bit depth may refer to:* For bit depth in graphics, see color depth* For bit depth in audio, see audio bit depth* For bit depth in drilling for petroleum, see drilling rig...
of 8 bits.
DNxHD data is typically stored in an MXF
MXF
Material eXchange Format is a container format for professional digital video and audio media defined by a set of SMPTE standards.- A brief summary of MXF :...
container, although it can also be stored in a Quicktime
QuickTime
QuickTime is an extensible proprietary multimedia framework developed by Apple Inc., capable of handling various formats of digital video, picture, sound, panoramic images, and interactivity. The classic version of QuickTime is available for Windows XP and later, as well as Mac OS X Leopard and...
container.
On February 13, 2008 Avid reported that DNxHD was approved as compliant with the SMPTE VC3 standard.
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
Filmlight
FilmLight Limited is a digital cinema technology company started in 2002 by the Scientific and Technical Academy Award-winning former Computer Film Company R&D team.Their main products are:...
, Harris Corporation
Harris Corporation
Harris Corporation is a Florida-based international communications equipment company that produces wireless equipment, electronic systems, and both terrestrial and spaceborne antennas for use in the government, defense, and commercial sectors. It is also the largest private-sector employer in...
, JVC
JVC
, usually referred to as JVC, is a Japanese international consumer and professional electronics corporation based in Yokohama, Japan which was founded in 1927...
, Seachange and EVS Broadcast Equipment
EVS Broadcast Equipment
EVS Broadcast Equipment SA manufactures live outside broadcast digital video production systems.Its recorders have become the dominant standard for broadcasters worldwide...
.
Implementations
DNxHD was first supported in Avid DS NitrisAvid DS Nitris
Avid DS is a high-end offline and finishing system comprising a non-linear editing system and visual effects software. It was developed by Softimage in Montreal...
(Sept 2004), then Avid Media Composer Adrenaline with the DNxcel option (Dec 2004) and finally by Avid Symphony Nitris (Dec 2005). Xpress Pro
Xpress Pro
Avid Xpress Pro was a non-linear video editing software aimed at professionals in the TV and movie industry. It was available for Microsoft Windows PCs and Apple Macintosh computers....
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's Editcam
Editcam
Editcam is a professional digital camera system manufactured by Ikegami and first introduced in 1995, available both as professional camcorders and modular dock recorders...
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.
A standalone Quicktime codec for both Windows XP
Windows XP
Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...
and Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
is available to create and play Quicktime files containing DNxHD material.
Since September 2007 the open source
Open source
The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...
FFmpeg
FFmpeg
FFmpeg is a free software project that produces libraries and programs for handling multimedia data. The most notable parts of FFmpeg are libavcodec, an audio/video codec library used by several other projects, libavformat, an audio/video container mux and demux library, and the ffmpeg command line...
project is providing 8-bit (but not 10-bit) VC-3/DNxHD encoding and decoding features thanks to BBC Research who sponsored the project and Baptiste Coudurier who implemented it. It is included in stable version 0.5 of FFmpeg, released on March 10, 2009. (ffmpeg -i
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
non-linear video editors Cinelerra
Cinelerra
Cinelerra is prosumer video editing software. It is designed for the GNU/Linux operating system. It is produced by Heroine Virtual, and is free software distributed under the GNU General Public License...
and Kdenlive
Kdenlive
Kdenlive is an open source video editing software package based on the MLT Framework that focuses on flexibility and ease of use...
to use DNxHD.
Technical details
DNxHD is very similar to JPEGJPEG
In computing, JPEG . The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality....
. Every frame is independent and consists of VLC-coded DCT
Discrete cosine transform
A discrete cosine transform expresses a sequence of finitely many data points in terms of a sum of cosine functions oscillating at different frequencies. DCTs are important to numerous applications in science and engineering, from lossy compression of audio and images A discrete cosine transform...
coefficients.
Header consists of many parts and may include quantization tables and 2048 bits of user data. Also each frame has two GUIDs and timestamp. The frame header is packed into big-endian dwords. Actual frame data consists of packed macroblocks using a technique almost identical to JPEG
JPEG
In computing, JPEG . The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality....
: 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.
VC-3
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:- SMPTE 2019-1-2008 VC-3 Picture Compression and Data Stream Format
- SMPTE 2019-3-2008 VC-3 Type Data Stream Mapping Over SDTI
- SMPTE 2019-4-2009 Mapping VC-3 Coding Units into the MXF Generic Container
- RP (Recommended Practices) 2019-2-2009 VC-3 Decoder and Bitstream Conformance