Dirac (and Dirac Pro, a subset standardised as

SMPTE The Society of Motion Picture and Television Engineers (SMPTE) (, rarely ), founded by Charles Francis Jenkins in 1916 as the Society of Motion Picture Engineers or SMPE, is a global professional association of engineers, technologists, and e ...

VC-2) is an open and

royalty-free Royalty-free (RF) material subject to copyright or other intellectual property rights may be used without the need to pay royalties or license fees for each use, per each copy or volume sold or some time period of use or sales. Computer standards ...

video compression format A video coding format (or sometimes video compression format) is a content representation format of digital video content, such as in a data file or bitstream. It typically uses a standardized video compression algorithm, most commonly based o ...

, specification and software

video codec A video codec is software or Computer hardware, hardware that data compression, compresses and Uncompressed video, decompresses digital video. In the context of video compression, ''codec'' is a portmanteau of ''encoder'' and ''decoder'', while ...

developed by

BBC Research & Development BBC Research & Development is the technical research department of the BBC. Function It has responsibility for researching and developing advanced and emerging media technologies for the benefit of the corporation, and wider UK and European m ...

. Dirac aimed to provide high-quality video compression for Ultra HDTV and competed with existing formats such as

H.264 Advanced Video Coding (AVC), also referred to as H.264 or MPEG-4 Part 10, is a video compression standard based on block-oriented, motion-compensated coding. It is by far the most commonly used format for the recording, compression, and d ...

. The specification was finalised in January 2008, and further developments were only bug fixes and constraints. In September of that year, version 1.0.0 of an

I-frame In the field of video compression, a video frame is compressed using different algorithms with different advantages and disadvantages, centered mainly around amount of data compression. These different algorithms for video frames are called pict ...

only subset known as Dirac Pro was released and was standardised by the

as VC-2. Version 2.2.3 of the full Dirac specification, including

motion compensation Motion compensation in computing is an algorithmic technique used to predict a frame in a video given the previous and/or future frames by accounting for motion of the camera and/or objects in the video. It is employed in the encoding of video ...

and inter-frame coding, was issued a few days later. Dirac Pro was used internally by the BBC to transmit HDTV pictures at the Beijing Olympics in 2008. Two

open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...

and royalty-free

software implementations, libschrodinger and dirac-research, were developed. The format implementations were named in honour of the theoretical physicists

Paul Dirac Paul Adrien Maurice Dirac ( ; 8 August 1902 – 20 October 1984) was an English mathematician and Theoretical physics, theoretical physicist who is considered to be one of the founders of quantum mechanics. Dirac laid the foundations for bot ...

and

Erwin Schrödinger Erwin Rudolf Josef Alexander Schrödinger ( ; ; 12 August 1887 – 4 January 1961), sometimes written as or , was an Austrian-Irish theoretical physicist who developed fundamental results in quantum field theory, quantum theory. In particul ...

, who shared the 1933

Nobel Prize in Physics The Nobel Prize in Physics () is an annual award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions to mankind in the field of physics. It is one of the five Nobel Prizes established by the ...

Technology

Dirac supports resolutions of

HDTV High-definition television (HDTV) describes a television or video system which provides a substantially higher image resolution than the previous generation of technologies. The term has been used since at least 1933; in more recent times, it ref ...

(1920×1080) and greater, and is claimed to provide significant savings in data rate and improvements in quality over video compression formats such as

MPEG-2 Part 2 H.262 or MPEG-2 Part 2 (formally known as ITU-T Recommendation H.262 and ISO/IEC 13818-2, also known as MPEG-2 Video) is a video coding format standardised and jointly maintained by ITU-T Study Group 16 Video Coding Experts Group (VCEG) and ISO ...

MPEG-4 Part 2 MPEG-4 Part 2, MPEG-4 Visual (formally International Organization for Standardization, ISO/International Electrotechnical Commission, IEC 14496-2) is a video encoding specification designed by the Moving Picture Experts Group (MPEG). It belongs to ...

and its competitors such as

Theora Theora is a free lossy video compression format. It was developed by the Xiph.Org Foundation and distributed without licensing fees alongside their other free and open media projects, including the Vorbis audio format and the Ogg contai ...

and

WMV Windows Media Video (WMV) is a series of video codecs and their corresponding video coding formats developed by Microsoft. It is part of the Windows Media framework. WMV consists of three distinct codecs: the original video compression technolog ...

. Dirac's implementers made a preliminary claim of "a two-fold reduction in bit rate over MPEG-2 for high definition video", which makes it comparable to

VC-1 SMPTE 421, informally known as VC-1, is a video coding format. Most of it was initially developed as Microsoft's proprietary video format Windows Media Video 9 in 2003. With some enhancements including the development of a new Advanced Profile, ...

and simpler profiles of

. Dirac supports both

constant bit rate Constant bitrate (CBR) is a term used in telecommunications, relating to the quality of service. Compare with variable bitrate. When referring to codecs, constant bit rate encoding means that the rate at which a codec's output data should be cons ...

and

variable bit rate Variable bitrate (VBR) is a term used in telecommunications and computing that relates to the bitrate used in sound or video encoding. As opposed to constant bitrate (CBR), VBR files vary the amount of output data per time segment. VBR allows ...

operation. When the low delay syntax is used, the bit rate will be constant for each area (Dirac slice) in a picture to ensure constant latency. Dirac supports

lossy In information technology, lossy compression or irreversible compression is the class of data compression methods that uses inexact approximations and partial data discarding to represent the content. These techniques are used to reduce data size ...

and

lossless Lossless compression is a class of data compression that allows the original data to be perfectly reconstructed from the compressed data with no loss of information. Lossless compression is possible because most real-world data exhibits statisti ...

compression modes. Dirac employs wavelet compression, like the

JPEG 2000 JPEG 2000 (JP2) is an image compression standard and coding system. It was developed from 1997 to 2000 by a Joint Photographic Experts Group committee chaired by Touradj Ebrahimi (later the JPEG president), with the intention of superseding their ...

and PGF image formats and the

Cineform CineForm Intermediate is an open source (from October 2017) video codec developed for CineForm Inc by David Taylor, David Newman and Brian Schunck. On March 30, 2011, the company was acquired by GoPro which in particular wanted to use the 3D film c ...

professional video codec, instead of the

discrete cosine transform A discrete cosine transform (DCT) expresses a finite sequence of data points in terms of a sum of cosine functions oscillating at different frequency, frequencies. The DCT, first proposed by Nasir Ahmed (engineer), Nasir Ahmed in 1972, is a widely ...

s used in

MPEG The Moving Picture Experts Group (MPEG) is an alliance of working groups established jointly by International Organization for Standardization, ISO and International Electrotechnical Commission, IEC that sets standards for media coding, includ ...

compression formats. Two of the specific wavelets Dirac can use are nearly identical to JPEG 2000's (known as the 5/3 and 9/7 wavelets), as well as two more derived from them. Dirac can be used in

Ogg Ogg is a digital multimedia container format designed to provide for efficient streaming and manipulation of digital multimedia. It is maintained by the Xiph.Org Foundation and is free and open, unrestricted by software patents. Its name is ...

and

Matroska Matroska (styled Matroška) is a project to create a container format that can hold an unlimited number of video, audio, picture, or subtitle tracks in one file. The Matroska Multimedia Container is similar in concept to other containers like ...

container formats and is also registered for use in the ISO base media (MP4) file format and

MPEG transport stream MPEG transport stream (MPEG-TS, MTS) or simply transport stream (TS) is a standard digital container format for transmission and storage of audio, video, and Program and System Information Protocol (PSIP) data. It is used in broadcast syst ...

Patents

The BBC does not own any patents on Dirac. They previously had some patent applications with plans to irrevocably grant a royalty-free licence for their Dirac-related patents to everyone, but they let the applications lapse. In addition, the developers have said they will try to ensure that Dirac does not infringe on any third party patents, enabling the public to use Dirac for any purpose.

VC-2

Dirac Pro, an

only subset of the Dirac specification, was proposed to the SMPTE for standardisation. Dirac Pro is designed for professional and studio use of high definition video in high bitrate applications. In 2010, the SMPTE standardised Dirac Pro as VC-2. Although work on the original Dirac codec has largely stopped, the VC-2 codec has continued to be adapted and updated for HD and UHD post-production environments. The SMPTE standards (ST) and recommended practices (RP) are as follows: * SMPTE ST 2042-1:2022 – VC-2 Video Compression * SMPTE ST 2042-2:2017 – VC-2 Level Definitions * SMPTE RP 2042-3:2022 – VC-2 Conformance Specification * SMPTE ST 2042-4:2018 — Mapping a VC-2 Stream into the MXF Generic Container * SMPTE RP 2047-1:2023 – VC-2 Mezzanine Level Compression of 1080P High Definition Video Sources * SMPTE ST 2047-2:2010 — Carriage of VC-2 Compressed Video over HD-SDI * SMPTE RP 2047-3:2023 — VC-2 Level 65 Compression of High Definition Video Sources for Use with a Standard Definition Infrastructure * SMPTE ST 2047-4:2011 — Carriage of Level 65 VC-2 Compressed Video Over the SDTV SDI * SMPTE RP 2047-5:2022 — VC-2 Level 66 Compression of Ultra-High Definition Video Sources for Use with a High Definition Infrastructure * IETF — RTP Payload Format for VC-2 High Quality (HQ) Profile

Software implementations

Two software implementations were initially developed. The BBC's reference implementation, initially called ''Dirac'' but renamed ''dirac-research'' to avoid confusion, was written in C++ and released under the

Mozilla Public License The Mozilla Public License (MPL) is a free and open-source weak copyleft license for most Mozilla Foundation software such as Firefox and Thunderbird. The MPL is developed and maintained by Mozilla, which seeks to balance the concerns of bo ...

GNU GPL The GNU General Public Licenses (GNU GPL or simply GPL) are a series of widely used free software licenses, or ''copyleft'' licenses, that guarantee end users the freedom to run, study, share, or modify the software. The GPL was the first ...

2 and

GNU LGPL The GNU Lesser General Public License (LGPL) is a free-software license published by the Free Software Foundation (FSF). The license allows developers and companies to use and integrate a software component released under the LGPL into their own ...

free software license A free-software license is a notice that grants the recipient of a piece of software extensive rights to modify and redistribute that software. These actions are usually prohibited by copyright law, but the rights-holder (usually the author) ...

s. Version 1.0.0 of this implementation was released on 17 September 2008 and defines the Dirac bitstream format. A second implementation called ''Schrödinger'' was funded by the BBC and aimed to provide a high-performance, portable version of the codec whilst remaining 100% bitstream compatible. Schrödinger was written in ANSI C and released under the same licenses as dirac-research, as well as the highly-permissive

MIT License The MIT License is a permissive software license originating at the Massachusetts Institute of Technology (MIT) in the late 1980s. As a permissive license, it puts very few restrictions on reuse and therefore has high license compatibility. Unl ...

GStreamer GStreamer is a Pipeline (computing), pipeline-based multimedia framework that links together a wide variety of media processing systems to complete complex workflows. For instance, GStreamer can be used to build a system that reads files in one f ...

plugins were included to enable the library to be used with that framework. On 22 February 2008, Schrödinger 1.0.0 was released, and was able to decode HD720/25p in real-time on a

Core Duo Intel Core is a line of multi-core (with the exception of Core Solo and Core 2 Solo) central processing units (CPUs) for midrange, embedded, workstation, high-end and enthusiast computer markets marketed by Intel Corporation. These processors ...

laptop. By the March 2010 release of Schrödinger version 1.0.9, it was outperforming dirac-research "in most encoding situations, both in terms of encoding speed and visual quality". With that release, most of the encoding tools in dirac-research were ported over to Schrödinger, giving Schrödinger the same as or better compression efficiency than dirac-research. Development of Schrödinger ceased after the 1.0.11 release in 2012. After the standardisation of Dirac Pro as SMPTE VC-2, development began on an open source reference VC-2 encoder. The code is provided in a git repository by the BBC and is available on

GitHub GitHub () is a Proprietary software, proprietary developer platform that allows developers to create, store, manage, and share their code. It uses Git to provide distributed version control and GitHub itself provides access control, bug trackin ...

. An encoder quality testing system has been put in place at BBC to check how well new encoding tools work and to make sure bugs that affect quality are quickly fixed.

Desktop playback and encoding

Dirac video playback is supported by

VLC media player VLC media player (previously the VideoLAN Client) is a free and open-source software, free and open-source, software portability, portable, cross-platform media player software and streaming media Server (computing), server developed by the Vide ...

since version 0.9.2 (2008), and by applications using the

framework. Support has also been added to

FFmpeg FFmpeg is a free and open-source software project consisting of a suite of libraries and programs for handling video, audio, and other multimedia files and streams. At its core is the command-line ffmpeg tool itself, designed for processing vide ...

. Applications which can encode to Dirac include

, MediaCoder,

LiVES Lives may refer to: * The plural form of a ''life'' * Lives, Iran, a village in Khuzestan Province, Iran * The number of lives in a video game * ''Parallel Lives'', aka ''Lives of the Noble Greeks and Romans'', a series of biographies of famous m ...

and

OggConvert OggConvert is a free and open-source transcoder for digital audio and video files of various types into the free Ogg Vorbis audio format, and the Theora, VP8 and Dirac video formats. It supports Ogg, Matroska and WebM containers for output. It ...

Performance

The algorithms in the original Dirac specification were intended to provide compression performance comparable to mainstream video compression standards of the time. A 2009 comparison of the Dirac and H.264 codecs, which used implementations from the second quarter of 2008, showed

x264 x264 is a free and open-source software library and a command-line utility developed by VideoLAN for encoding video streams into the H.264/MPEG-4 AVC video coding format. It is released under the terms of the GNU General Public License. Histo ...

scoring slightly higher than Dirac. Another 2009 comparison found similar results for standard definition content, but did not compare high definition (HD) video content. These studies show that Dirac compression performance is close to that of

Advanced Simple Profile (ASP, popularised as

DivX DIVX (Digital Video Express) is a discontinued digital video format. Created in part by Circuit City, it was an unsuccessful attempt to create an alternative to video rental in the United States. The format's poor reception from consumers resu ...

). While also approaching low complexity H.264 encodes, a High Profile H.264 encoded video will have better compression for the same perceived quality. Since 2010, royalty-free, open source video codecs such as

VP8 VP8 is an open format, open and royalty-free Video coding format, video compression format released by On2 Technologies in 2008. Initially released as a Proprietary software, proprietary successor to On2's previous VP7 format, VP8 was released a ...

, VP9, and

AV1 AOMedia Video 1 (AV1) is an open, royalty-free video coding format initially designed for video transmissions over the Internet. It was developed as a successor to VP9 by the Alliance for Open Media (AOMedia), a consortium founded in 2015 tha ...

have been developed with better compression performance and more widespread adoption, including dominant streaming services such as

YouTube YouTube is an American social media and online video sharing platform owned by Google. YouTube was founded on February 14, 2005, by Steve Chen, Chad Hurley, and Jawed Karim who were three former employees of PayPal. Headquartered in ...

and

Netflix Netflix is an American subscription video on-demand over-the-top streaming service. The service primarily distributes original and acquired films and television shows from various genres, and it is available internationally in multiple lang ...

References

External links

*
BBC Research & Development page on VC-2
{{Compression Software Implementations BBC Research & Development Free video codecs Lossless compression algorithms SMPTE standards Wavelets Open formats