Avid DNxHD ("Digital Nonlinear Extensible High Definition") is a lossy high-definition video post-production codec developed by Avid for multi-generation compositing with reduced storage and bandwidth requirements. It is an implementation of the SMPTE VC-3 standard.
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 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 VC-3 standard.
DNxHD is intended to be an open standard, but as of March 2008, it 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.
On September 14, 2014, at the Avid Connect event in Amsterdam, Netherlands, Avid announced the DNxHR codec to support resolutions greater than 1080p, such as 2K and 4K.
On December 22, 2014, Avid Technology released an update for Media Composer that added support for 4K resolution, the Rec. 2020 color space, and a bit rate of up to 3,730 Mbit/s with the DNxHR codec.
DNxHD is very similar to JPEG. Every frame is independent and consists of VLC-coded DCT coefficients.
The header consists of many parts and may include quantization tables and 2048 bits of user data. Each frame also has two GUIDs and timestamps. 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.