If you’ve been following any of the leaks surrounding the upcoming Google Chromecast HD, you may have seen a lot of excitement around rumored support for the AV1 codec. While it is indeed a pretty big step forward from codecs like H264 and VP9, there’s a lot more to the story than that. AV1, also known as AOMedia Video 1, was first released in March of 2018, and it’s been a slow road in its adoption across the industry. This is the entire story of AV1, how it improves over VP9 and H.264, and why it’s a big deal.
What is AV1?
AV1 is a codec developed by the Alliance for Open Media, a conglomerate of a ton of different companies in the technology space. Its main benefits are that it’s royalty-free (so, companies can implement it in their software for free), and it has some immense savings over the likes of VP9 and H264. Facebook Engineering conducted tests in 2018, concluding that the AV1 reference encoder achieved 34%, 46.2%, and 50.3% higher data compression than libvpx-vp9, x264 High profile, and x264 Main profile, respectively. This means that for those on slower connections, you may be able to enjoy a quality higher than what you’re used to, and for those on faster connections, you’ll be able to get an even higher bitrate on the same connection speed.
The first smartphone chipset to support AV1 decode was the MediaTek Dimenisty 1000, which supported up to 4K 60 FPS. The Nvidia Geforce 3000 series supported decoding, the new Nvidia Geforce 4000 series supports both encoding and decoding, and Samsung’s Exynos 2100/2200 both support AV1 decode as well. Support is slowly growing in the industry, and the chipset purported to be in the Chromecast HD also supports AV1 decode, too. That doesn’t mean Google will implement support for it, but it’s looking likely. For people on limited connections, that’s an upgrade over VP9 and H264.
Not only that, but YouTube on desktop also supports AV1, and you can enable it in your account settings so long as you’re using a compatible browser. In fact, the company has designed its own silicon for the encoding of AV1 video that will be used in data centers for YouTube. The chip, code-named “Argos”, is a second-gen Video (trans) Coding Unit (VCU) that converts videos uploaded to the platform to various compression formats and optimizes them for different screen sizes. Google claims that its new Argos VCU can handle videos 20-33 times more efficiently than conventional servers.
The history of AV1
The context behind AV1 and why it was created is important as well. VP9 is a royalty-free codec developed by Google that anyone can use, and because it’s royalty-free, it could be implemented on any platform or service that wanted it. YouTube made use of the codec on any device that could support it (as that meant big savings for Google thanks to reduced bandwidth), and it has even been adopted by video-on-demand services such as Netflix, Twitch, and Vimeo.
However, because Google has a vested interest in adopting better compression algorithms to reduce the bandwidth usage of its data centers, it began to work on VP10 — the successor to VP9. A tiny increase in video compression per video can result in huge cost savings and a major improvement in user experience when you’re accounting for billions of video minutes. Google announced that they planned to release VP10 in 2016, and then would release an update every 18 months to ensure a steady progression. It got to the point where Google even started to release code for VP10, but the company announced the cancellation of VP10 and formed the Alliance for Open Media (AOMedia) instead.
The Alliance for Open Media includes everyone from processor designers (AMD, Arm, Broadcom, Chips&Media, Intel, Nvidia) to browser developers (Google, Microsoft, and Mozilla), to streaming and videoconferencing services (Adobe, Amazon, BBC R&D, Cisco, Netflix, Youtube). All of these companies have been offering up some form of support to AV1, be it through hardware decoders introduced in chipsets, the implementation of decoders in browsers, or the use of the codec on streaming services.
AV1 versus HEVC/H265
The biggest difference between AV1 and HEVC (High-Efficiency Video Coding), also known as H.265, is in the licensing. In order to ship a product with HEVC support, you need to acquire licenses from at least four patent pools (MPEG LA, HEVC Advance, Technicolor, and Velos Media) as well as numerous other companies, many of which do not offer standard licensing terms — instead requiring you to negotiate terms.
These steep royalties were already problematic for products like Google Chrome, Opera, Netflix, Amazon Video, Cisco WebEx Connect, Skype, and others, and they completely exclude HEVC as an option for projects like Mozilla Firefox. This is because it goes against multiple core values of the Firefox project: Firefox needs to be royalty-free in order to ship in many FOSS projects, which HEVC usage would prevent it from being; and Mozilla believes in a free and open web, and that isn’t possible if you promote patent-encumbered standards. Even ignoring those two problems, Mozilla simply cannot afford to waste hundreds of millions of dollars on royalties and all that time negotiating the necessary licensing agreements.
A fun fact as well, these same problems are what prevented Firefox (and Chromium) from even including native H.264 playback on many platforms until a couple of years ago… and it still requires a plugin on Linux. It’s unlikely that Firefox will even be able to support HEVC before its patents expire in the 2030s (or possibly even later). Even to this day, Firefox only supports H.264 natively thanks to Cisco offering to pay all of the licensing costs for Mozilla through OpenH264, in order to standardize H.264 for streaming across the market until the next generation codec was ready. On the Mozilla video codec guide, the company says that “Mozilla will not support HEVC while it is encumbered by patents.” To this day, only Edge and Internet Explorer support native HEVC playback, and only on specific hardware that supports decoding.
In efficiency terms, both codecs go toe-to-toe against each other. Their efficiency is generally on-par with each other (though tests have shown AV1 to edge slightly ahead), but there’s a catch — AV1 typically takes significantly longer to encode, thanks to the lack of hardware encoding capabilities. The University of Waterloo found in 2020 that while AV1 offered a bitrate saving of 9.5% when compared to HEVC in encoding a 4K video, AV1 videos also took 590-times longer to encode than AVC. In contrast, HEVC took only 4.2-times longer. These tests were obviously run quite early on in AV1’s lifespan when hardware support wasn’t really available.
The future of AV1
It’s looking likely that AV1 will blaze the trail for high-quality compressed video playback, as more and more devices support hardware decoding. Given that HEVC is only supported by one browser on desktop (now that Internet Explorer is dead, anyway), AV1 is clearly the go-to codec for the future as a VP9 successor. With support only expected to grow, more and more devices are going to end up using it. There are already some experiment flags referring to AV2 on the AOM repository and a “starting anchor for AV2 research” that was committed to the repository last year, which suggests that we’ll see iterations in the future as well.
Why does AV1 matter for the Google Chromecast HD?
If you’re looking to pick up the Google Chromecast HD, there’s one big reason why you might care about AV1 — and that’s your network capabilities. If you’re buying the HD version instead of the 4K version, there are likely a couple of reasons why you would do that, and one of them may be that your internet does not have the bandwidth for 4K streaming. If that is the case, then you’re likely to be bandwidth-conscious anyway, and AV1 means that you can get higher bitrate video out of your Chromecast. This will lead to better video quality overall at the same data rates that your internet already supports.
The Chromecast with Google TV (HD) is a cheaper Chromecast that can only do 1080p playback, but for a lot of people, that's all you need.
Not only that, though, and this is an arguably even bigger reason, it’s the first really mainstream TV dongle that could actively support AV1. Roku is mainstream to a certain degree but harder to get in some regions, and the Fire TV Stick 4K Max is the only other option currently. Google’s ecosystem for its TV dongles is by far the most fleshed out of any of them, and the inclusion of AV1 is a pretty big deal for that reason, too. It legitimizes it as an option, and may push other companies to support AV1 in other ways, too.
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