Netflix has started streaming content encoded with AV1. This specifically concerns streaming to televisions. Earlier, the company already started streaming via this codec to, among other things, the Android mobile app.
In an explanation to a blog, Netflix does not provide further details about bit rates that subscribers with suitable televisions can expect. The company only emphasizes that AV1 is more efficient than other codecs, such as the also used HEVC and MPEG4 AVC, and that it makes it possible to deliver videos with improved visual quality at the same bitrate. That suggests that the streaming service does not seem to plan to use higher bitrates. The company will probably mainly use the new codec to improve the experience of image quality, without this being accompanied by a higher bit rate.
In that context, Netflix says it expects higher VMAF scores to be achieved. That stands for Video Multimethod Assessment Fusion and is a Netflix quality measure for evaluating the video quality of the decoded image relative to the reference image. The Quality Score perceived by the users is estimated based on a number of factors such as anti-noise, loss of detail and the visual fidelity of the image. The higher this score, the more beautiful the image is experienced.
Netflix usually tries to get the highest possible VMAF at the lowest possible bitrate. The fact that the company will probably not use AV1 in combination with higher bit rates is also confirmed in this respect by the comment that the improvement through the use of AV1 is especially significant in sessions with significant network congestion and with the lowest visual quality. In those situations, the AV1 streams would improve the quality up to 10 VMAF without affecting the rebuffer rate.
Netflix also reports that on some televisions the noticeable decreases in quality were reduced by 38 percent. On average, a 2 percent reduction in playback delays was observed when the AV1 codec was deployed. These kinds of improvements come from the efficiency of AV1, which requires less bandwidth and thus a certain level of image quality can be maintained for longer.
With the use of AV1 for the streams to televisions, Netflix expects to reach tens of millions of subscribers. Customers must have a television with a decoder that supports AV1. There are already quite a few televisions on the market, but it usually concerns televisions from 2020 and in particular 2021. Sony, Philips and Panasonic, for example, do have models with AV1 decoding, but they all only came out this year.
In addition, Netflix is not able to compress all content via AV1 in one fell swoop. The current catalog has become too large for that, which means that it takes a lot of computing power and time. As a result, the company makes a selection, with the popularity of the title, among a few other factors, determining how quickly it will be made available through AV1. Popular content will therefore become available faster than content with fewer viewers.
AV1 was developed by the Alliance for Open Media. This organization was founded in 2015 by Microsoft, Google, Intel, Mozilla, Amazon, Netflix and Nvidia with the goal of developing a better video compression method more suitable for delivering content over networks. Later, Apple also joined the alliance, as did Samsung. The specification for the AV1 codec was released in March 2018. The technology is released under an open source license and can be used without having to pay royalties.