AOMedia Video 1
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 leading firms from the semiconductor industry, video on demand providers, and web browser developers, founded in 2015. It is the primary contender for standardisation by the video standard working group NetVC of the Internet Engineering Task Force (IETF). The group has put together a list of criteria to be met by the new video standard. It is meant to succeed its predecessor VP9 and compete with HEVC/H.265 from the Moving Picture Experts Group.
The purpose of AV1 is to be as good as possible under royalty-free patent licensing. Crucial to this objective is therefore to ensure, during development, that it does not infringe on patents of competing companies. This contrasts to its main competitor HEVC, for which IPR review was not part of the standardization process. The latter practice is stipulated in ITU-T's definition of an open standard. The case of HEVC's independent patent pools has been characterized by critical observers as a failure of price management.
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 doesn't engage in patent litigation. As a defensive condition, anyone engaging in patent litigation loses the right to the patents of all patent holders.
It aims for state of the art performance with a noticeable compression efficiency advantage at only slightly increased coding complexity. The efficiency goal is 25% improvement over HEVC. At the beginning of June 2016 its performance was already comparable to HEVC as measured using the objective metric PSNR-HVS-M.
It 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 10 and 12 bits of precision per color component.
AV1 is a traditional block-based frequency transform format featuring new techniques taken from several experimental formats that are testing technology for a next-generation format after HEVC and VP9. Based on Google's experimental VP9 evolution project VP10, it will incorporate additional techniques developed in Xiph's/Mozilla's Daala and Cisco's Thor.
Doing internal processing in higher precision (10 or 12 bits per sample) leads to compression improvement due to smaller rounding errors in reference imagery. For intra prediction, there are more (than 8) angles for directional prediction and weighted filters for per-pixel extrapolation. Temporal prediction can use more references. Prediction can happen for bigger units (≤128×128) and they can be subpartitioned in more ways. Predictions can be combined in more advanced ways (than a uniform average) in a block, including smooth and sharp gradients in different directions. This allows either inter-inter or inter-intra predictions to be combined in the same block. Conventional scalar quantisation with binary arithmetic coding is currently used, inherited from VP9, but experiments are ongoing to investigate other systems including mutisymbol coding, and Perceptual Vector Quantization from Daala. Asymmetric Numeral Systems coding is being considered for the entropy coding phase. For the in-loop filtering step it has a deblocking filter and experimental deringing filters from both Thor and Daala.
The first official announcement of the project came with the press release on the formation of the Alliance. The growing usage of its predecessor VP9 is attributed to confidence in the Alliance and (the development of) AV1 as well as the pricey and complicated licensing situation of MPEG's competitor HEVC.
The roots of the project precede the Alliance, however. Individual contributors started experimental technology platforms years before: Daala already published code in 2010, VP10 was announced on September 12, 2014, and Thor was published on August 11, 2015. The first version 0.1.0 of the AV1 reference codec was published on April 7, 2016.
In April 2017, using the 8 currently enabled experimental features (of 77 total), Bitmovin was able to demonstrate favorable objective metrics, as well as visual results, compared to HEVC on the Sintel animated film.
It is expected that Alliance members have interest in adopting the format, in respective ways, once the bitstream is frozen. The member companies represent several industries, including browser vendors (Google, Mozilla, Microsoft), content providers (Google, Netflix, Amazon) and hardware manufacturers (Intel, AMD, ARM, Nvidia).
Video streaming service YouTube declared intent to transition to the new format as fast as possible, starting with highest resolutions within six months after the finalization of the bitstream format.
Like its predecessor VP9, AV1 will be used together with the WebM and Opus formats. These are well supported among web browsers, with the exception of Safari (desktop and mobile editions) and the discontinued Internet Explorer (prior to Edge) (see VP9 in HTML5 video § browser support).
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The beginning of the end of HEVC/H.265 video codec
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... Once available, YouTube expects to transition to AV1 as quickly as possible, particularly for video configurations such as UHD, HDR, and high frame rate videos ... Based upon its experience with implementing VP9, YouTube estimates that they could start shipping AV1 streams within six months after the bitstream is finalized. ...
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- Converse, Alex (16 November 2015). "New video coding techniques under consideration for VP10 – the successor to VP9". YouTube. Retrieved 3 December 2016.
- Jean-Marc Valin (Xiph.org/Mozilla), June 6, 2016: Revisiting Daala Technology Demos
- "Bitmovin Supports AV1 Encoding for VoD and Live and Joins the Alliance for Open Media". 18 April 2017. Retrieved 20 May 2017.
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