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AOMedia Video 1

An open, royalty-free video coding format designed for video transmissions over the Internet.
Av1 Logo 2018

AOMedia Video 1 (AV1) is an open, royalty-free video coding format 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 that includes semiconductor firms, video on demand providers, video content producers, software development companies and web browser vendors. The AV1 bitstream specification includes a reference video codec. In 2018 Facebook testing that approximates real-world conditions, AV1 achieved 34%, 46.2%, and 50.3% higher data compression than libvpx-vp9, x264 high profile, and x264 main profile respectively.

Industry observers found one of the most compelling features of AV1 to be its royalty-free licensing model, unlike existing technologies such as HEVC that require royalty payments and prevent widespread adoption in open-source projects.

Cisco's Thor development was started in response to HEVC being perceived as unviable for use in open source and freely distributed products, but the work of Google and Mozilla (previously under Xiph) on royalty-free video predates this event and is not attributed to HEVC's licensing woes, although also seen as a problem by Mozilla.

History

The Alliance's motivations for creating AV1 included the high cost and uncertainty involved with the patent licensing of HEVC, the MPEG-designed codec expected to succeed AVC. Additionally, the Alliance's seven founding members – Amazon, Cisco, Google, Intel, Microsoft, Mozilla, and Netflix – announced that the initial focus of the video format would be the delivery of high-quality web video. The official announcement of AV1 came with the press release on the formation of the Alliance for Open Media on 1 September 2015. Only 42 days before, on 21 July 2015, HEVC Advance's initial licensing offer was announced to be an increase over the royalty fees of its predecessor, AVC. In addition to the increased cost, the complexity of the licensing process increased with HEVC. Unlike previous MPEG standards where the technology in the standard could be licensed from a single entity, MPEG-LA, when the HEVC standard was finished, two patent pools had been formed with a third pool was on the horizon. In addition, various patent holders were refusing to license patents via either pool, increasing uncertainty about HEVC's licensing. According to Microsoft's Ian LeGrow, an open-source, royalty-free technology was seen as the easiest way to eliminate this uncertainty around licensing.

The negative effect of patent licensing on free and open-source software has also been cited as a reason for the creation of AV1. For example, building a H.264 implementation into Firefox would prevent it from being distributed free of charge since licensing fees would have to be paid to MPEG-LA. Free Software Foundation Europe has argued that FRAND patent licensing practices make the free software implementation of standards impossible due to various incompatibilities with free software licenses.

Many of the components of the AV1 project were sourced from previous research efforts by Alliance members. Individual contributors started experimental technology platforms years before: Xiph's/Mozilla's Daala already published code in 2010, Google's experimental VP9 evolution project VP10 was announced on 12 September 2014, and Cisco's Thor were published on 11 August 2015. Building on the codebase of VP9, AV1 incorporates additional techniques, several of which were developed in these experimental formats. The first version 0.1.0 of the AV1 reference codec was published on 7 April 2016.

Although a soft feature freeze came into effect at the end of October 2017, several significant features were decided to continue developing beyond this. One of these in-progress features, the bitstream format, was projected to be frozen in January 2018 but was delayed due to unresolved critical bugs as well as further changes to transformations, syntax, the prediction of motion vectors, and the completion of legal analysis. The Alliance announced the release of the AV1 bitstream specification on 28 March 2018, along with a reference, software-based encoder, and decoder. On 25 June 2018, a validated version 1.0.0 of the specification was released. On 8 January 2019 a validated version 1.0.0 with Errata 1 of the specification was released.

Martin Smole from AOM member Bitmovin said that the computational efficiency of the reference encoder was the greatest remaining challenge after the bitstream format freeze had been completed. While still working on the format, the encoder was not targeted for production use and speed optimizations were not prioritized. Consequently, the early version of AV1 was orders of magnitude slower than existing HEVC encoders. Much of the development effort was consequently shifted towards maturing the reference encoder. In March 2019, it was reported that the speed of the reference encoder had improved greatly and within the same order of magnitude as encoders for other common formats.

Purpose

AV1 aims to be a video format for the web that is both states of the art and royalty-free. The mission of the Alliance for Open Media is the same as that of the WebM project.

To fulfill the goal of being royalty free, the development process requires that no feature can be adopted before it has been confirmed independently by two separate parties to not infringe on patents of competing companies. In cases where an alternative to a patent-protected technique is not available, owners of relevant patents have been invited to join the Alliance (even if they were already members of another patent pool). For example, Alliance members Apple, Cisco, Google, and Microsoft are also licensors in MPEG-LA's patent pool for H.264. As an additional protection for the royalty-free status of AV1, the Alliance has a legal defense fund to aid smaller Alliance members or AV1 licensees in the event they are sued for alleged patent infringement.

This development process contrasts with that of its main competitor, HEVC, where a review of the intellectual property rights (IPR review) was not part of the standardization process. The reviewing practice used by AV1 is stipulated in ITU-T's definition of an open standard.

A recurring concern in the field of royalty-free multimedia formats is the possibility that such formats may infringe upon patents unknown to their creators and users. The concern has been raised regarding AV1, and previously VP8, VP9, Theora and IVC. The problem of unforeseen patents is not unique to royalty-free formats, but it uniquely threatens their status as royalty-free. In contrast, IPR avoidance has not traditionally been a priority in MPEG's business model for royalty-bearing formats (although the MPEG chairman argues it has to change).

Under patent rules adopted from the World Wide Web Consortium (W3C), technology contributors license their AV1-connected patents to anyone, anywhere, anytime based on reciprocity (i.e. as long as the user does not engage in patent litigation). As a defensive condition, anyone engaging in patent litigation loses the right to the patents of all patent holders.

The creation of royalty-free web standards has been a long-stated pursuit for the industry. In 2007, the proposal for HTML5 video specified Theora as mandatory to implement. The reason was that public content should be encoded in freely implementable formats, if only as a "baseline format", and that changing such a baseline format later would be hard because of network effects. The Alliance for Open Media is a continuation of Google's efforts with the WebM project, which renewed the royalty-free competition after Theora had been surpassed by AVC. For companies such as Mozilla that distribute free software, AVC can be difficult to support as a per-copy royalty easily is unsustainable given the lack of revenue stream to support these payments in free software (see FRAND § Excluding costless distribution). Similarly, HEVC has not successfully convinced all licensors to allow an exception for freely distributed software (see HEVC § Provision for costless software).

The performance goals include "a step up from VP9 and HEVC" inefficiency for a low increase in complexity. NETVC's efficiency goal is 25% improvement over HEVC. The primary complexity concern is for software decoding since hardware support will take time to reach users. However, for WebRTC, live encoding performance is also relevant, which is Cisco's agenda: Cisco is a manufacturer of videoconferencing equipment, and their Thor contributions aim at "reasonable compression at only moderate complexity".

Feature-wise, AV1 is specifically designed for real-time applications (especially WebRTC) and higher resolutions (wider color gamuts, higher frame rates, UHD) than typical usage scenarios of the current generation (H.264) of video formats where it is expected to achieve its biggest efficiency gains. It is therefore planned to support the color space from ITU-R Recommendation BT.2020 and up to 12 bits of precision per color component. AV1 is primarily intended for lossy encoding, although lossless compression is supported as well.

AV1-based containers have also been proposed as a replacement for JPEG, similar to Better Portable Graphics and High-Efficiency Image File Format which wrap HEVC.

Key Terms

alliance
alliance open media
av1
avc
cisco
google
hevc
mozilla
patents
vp9

Additional Resources

No ressources found.

Acronymn

AV1

Synonymns

AOMedia Video 1
(none found)
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