Thor (video codec)

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Thor is a royalty free video codec under development by Cisco Systems. The specifications of Thor were available in various Internet-Drafts. [1]

A video codec is an electronic circuit or software that compresses or decompresses digital video. It converts uncompressed video to a compressed format or vice versa. In the context of video compression, "codec" is a concatenation of "encoder" and "decoder"—a device that only compresses is typically called an encoder, and one that only decompresses is a decoder.

Cisco Systems American multinational technology company

Cisco Systems, Inc. is an American multinational technology conglomerate headquartered in San Jose, California, in the center of Silicon Valley, that develops, manufactures and sells networking hardware, telecommunications equipment and other high-technology services and products. Through its numerous acquired subsidiaries, such as OpenDNS, WebEx, Jabber and Jasper, Cisco specializes into specific tech markets, such as Internet of Things (IoT), domain security and energy management.


On July 22, 2015, Thor was presented to the IETF as a candidate for their NETVC video standard. [2] Thor uses some Cisco elements that are also used by HEVC. [3] As part of the NETVC work, the Constrained Low-Pass Filter (CLPF) and motion compensation techniques used in Thor were tested in conjunction with the lapped transform coding techniques from the Daala codec. [4]

The Internet Video Codec (NETVC) is a standardization project for a royalty-free video codec hosted by the IETF. It is intended to provide a royalty-free alternative to industry standards such as MPEG-4 and HEVC that require licensing payments for many uses. The group has put together a list of criteria to be met by the new video standard. The VP9-based format AOMedia Video 1 (AV1) from the Alliance for Open Media is the primary contender for standardisation by the NetVC working group.

Motion compensation

Motion compensation 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 data for video compression, for example in the generation of MPEG-2 files. Motion compensation describes a picture in terms of the transformation of a reference picture to the current picture. The reference picture may be previous in time or even from the future. When images can be accurately synthesized from previously transmitted/stored images, the compression efficiency can be improved.

In signal processing, a lapped transform is a type of linear discrete block transformation where the basis functions of the transformation overlap the block boundaries, yet the number of coefficients overall resulting from a series of overlapping block transforms remains the same as if a non-overlapping block transform had been used.

On September 1, 2015, Cisco announced that the Alliance for Open Media would use elements of Thor to develop a royalty free video format, AOMedia Video 1. [5] [6] [7]

The Alliance for Open Media (AOMedia) is a non-profit industry consortium for the development of open, royalty-free technology for multimedia delivery headquartered in Wakefield, Massachusetts, USA. It adopts the principles of the development of open web standards for the creation of video standards that can serve as royalty-free alternatives to the hitherto dominant standards of the Moving Picture Experts Group (MPEG) and the related business model that exploits intellectual property through patent royalties and became associated with financial uncertainties, especially for internet companies and innovators.

According to Steinar Midtskogen (a principal Thor developer and AV1 contributor), Thor is in good shape for real-time CPU encoding (as of NETVC meeting 101, March 19th 2018), in strong contrast to AV1 at the same time. [8] Thor development had stalled for the finalization of AV1, but Midtskogen envisaged further Thor development by merging the Daala entropy coder and adding more tools for screen content. [9]

AV1 open, royalty-free video coding format

AOMedia Video 1 (AV1) is an open, royalty-free video coding format designed for video transmissions over the Internet. It is being developed by the Alliance for Open Media (AOMedia), a consortium of firms from the semiconductor industry, video on demand providers, and web browser developers, founded in 2015. The AV1 bitstream specification includes a reference video codec. It succeeds VP9. It can have 20% higher data compression than VP9 or HEVC/H.265 from the Moving Picture Experts Group and about 50% higher than the widely used AVC.

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FFmpeg multimedia framework

FFmpeg is a free software project consisting of a vast software suite of libraries and programs for handling video, audio, and other multimedia files and streams. At its core is the FFmpeg program itself, designed for command-line-based processing of video and audio files, and widely used for format transcoding, basic editing, video scaling, video post-production effects, and standards compliance. FFmpeg includes libavcodec, an audio/video codec library used by many commercial and free software products, libavformat (Lavf), an audio/video container mux and demux library, and the core ffmpeg command line program for transcoding multimedia files. FFmpeg is published under the GNU Lesser General Public License 2.1+ or GNU General Public License 2+.

Xiph.Org Foundation is a non-profit organization that produces free multimedia formats and software tools. It focuses on the Ogg family of formats, and the most successful one has been Vorbis, an open and freely licensed audio format and codec designed to compete with the patented WMA, MP3 and AAC. As of 2013, the current development work is focusing on Daala, an open and patent-free video format and codec designed to compete with VP9 and the patented High Efficiency Video Coding.

VP8 an open, royalty-free lossy video coding format released by Google in 2010

VP8 is an open and royalty free video compression format owned by Google and created by On2 Technologies as a successor to VP7.

SILK is an audio compression format and audio codec developed by Skype Limited. It was developed for use in Skype, as a replacement for the SVOPC codec. Since licensing out, it has also been used by others. It has been extended to the Internet standard Opus codec.

High Efficiency Video Coding (HEVC), also known as H.265 and MPEG-H Part 2, is a video compression standard, designed as a successor to the widely used AVC. In comparison to AVC, HEVC offers from 25% to 50% better data compression at the same level of video quality, or substantially improved video quality at the same bit rate. It supports resolutions up to 8192×4320, including 8K UHD, and unlike the primarily 8-bit AVC, HEVC's higher fidelity Main10 profile has been incorporated into nearly all supporting hardware. HEVC is competing with the AV1 coding format for standardization by the video standard working group NetVC of the Internet Engineering Task Force (IETF).

The HTML5 specification introduced the video element for the purpose of playing videos, partially replacing the object element. HTML5 video is intended by its creators to become the new standard way to show video on the web, instead of the previous de facto standard of using the proprietary Adobe Flash plugin, though early adoption was hampered by lack of agreement as to which video coding formats and audio coding formats should be supported in web browsers.

libvpx codec library implementing VP8, VP9, AV1

libvpx is a free software video codec library from Google and the Alliance for Open Media (AOMedia). It serves as the reference software implementation for the video coding formats VP8 and VP9, and for AV1 a special fork named libaom that was stripped of backwards compatibility.

WebP image file format

WebP is an image format employing both lossy and lossless compression. It is currently developed by Google, based on technology acquired with the purchase of On2 Technologies.

x265 HEVC/H.265 encoder

x265 is a library for encoding video into the High Efficiency Video Coding (HEVC/H.265) video compression format that was developed and standardized by the ISO/IEC MPEG and ITU-T VCEG. x265 is offered under either version 2 of the GNU General Public License (GPL) or a commercial license, similar to the x264 project.

A video coding format is a content representation format for storage or transmission of digital video content. Examples of video coding formats include MPEG-2 Part 2, MPEG-4 Part 2, H.264, HEVC, Theora, RealVideo RV40, VP9, and AV1. A specific software or hardware implementation capable of video compression and/or decompression to/from a specific video coding format is called a video codec; an example of a video codec is Xvid, which is one of several different codecs which implements encoding and decoding videos in the MPEG-4 Part 2 video coding format in software.

VP9 an open, royalty-free video coding format released by Google in 2012

VP9 is an open and royalty-free video coding format developed by Google.

Daala is a video coding format under development by the Xiph.Org Foundation under the lead of Timothy B. Terriberry mainly sponsored by the Mozilla Corporation. Like Theora and Opus, Daala is available free of any royalties and its reference implementation is being developed as free and open-source software.

OpenH264 is a free software library for real-time encoding and decoding video streams in the H.264/MPEG-4 AVC format. It is released under the terms of the Simplified BSD License.

High Efficiency Image File Format (HEIF) is a file format for individual images and image sequences. It was developed by the Moving Picture Experts Group (MPEG) and is defined by MPEG-H Part 12. The MPEG group claims that twice as much information can be stored in a HEIF image as in a JPEG image of the same size, resulting in a better quality image.

Internet Video Coding is a video coding standard. IVC was created by MPEG, and was intended to be a royalty-free video coding standard for use on the Internet, as an alternative to non-free formats such as AVC and HEVC. As such, IVC was designed to only use coding techniques which were not covered by royalty-requiring patents.

Versatile Video Coding (VVC) is a future video compression standard being developed for finalisation around 2020 by the Joint Video Exploration Team (JVET), a united video expert team of the MPEG consortium and the ITU. At times, it was also referred to as Future Video Coding (FVC) or as ITU H.266. It will be the successor to High Efficiency Video Coding / HEVC. The standardization process for the HEVC successor officially began in October 2017. At IBC 2018, a version of one codec was shown that compresses 40% more efficiently than HEVC.


  1. A. Fuldseth, G. Bjontegaard, M. Zanaty, e.a. (2016-03-18). "Thor Video Codec". IETF . Retrieved 2016-06-14.
  2. "NETVC IETF 93". Internet Engineering Task Force. Retrieved 2015-08-11.
  3. "Thor: High Efficiency, Moderate Complexity Video Codec using only RF IPR" (PDF). Internet Engineering Task Force. Retrieved 2015-08-11.
  4. NETVC Hackathon Results IETF 93 (Prague) (PDF)
  5. "New open standard for Ultra High Definition video will enable enhanced video playback". Alliance for Open Media. 2015-09-01. Retrieved 2015-09-01.
  6. Stephen Shankland (2015-09-01). "Tech giants join forces to hasten high-quality online video". CNET . Retrieved 2015-09-01.
  7. Zimmerman, Steven (15 May 2017). "Google's Royalty-Free Answer to HEVC: A Look at AV1 and the Future of Video Codecs". XDA Developers. Archived from the original on 14 June 2017. Retrieved 10 June 2017.
  8. "IETF101-NETVC-20180319-1550". 19 March 2018. Retrieved 23 May 2018. It's certainly possible to get real-time encoding with Thor, that we know, but for AV1, it's not proven yet.
  9. "Thor update and AV1 comparisons" . Retrieved 23 May 2018.

See also