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 replace Google's VP9 and compete with HEVC/H.265 from the Moving Picture Experts Group.
Contents
AV1 can be used together with the audio format Opus in a future version of the WebM format for HTML5 web video and WebRTC.
Features
The main distinguishing feature is its royalty-free (patent) licensing terms that set it apart, notably from its main competitor HEVC with its complicated and costly software patent licensing situation. Whether it can be convincingly argued that it does not infringe on patents of competing companies is seen as crucial for the chances for widespread adoption. 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 on his part doesn't engage in patent litigations.
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.
Technology
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 Alliance publishes a reference implementation written in C and assembly language (aomenc, aomdec) as free software under the terms of the BSD 2-Clause License.
History
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.
The bitstream format is projected to be frozen in Q4 of 2017. First compatible hardware components are expected to become available within 12 months after that.
Adoption
Most browsers, with two major exceptions (Internet Explorer and Safari, see HTML5 video § browser support), already support AV1's predecessor VP9 and associated WebM and Opus formats that will continue to be used with AV1.
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.
Companies from within the Alliance (AMD, ARM, Intel, Nvidia) are working on hardware support for decoding and encoding AV1.