Streaming Media
The need to deliver greater quality at lower bitrates—more bang for the buck—has never been greater, but leading video streaming platforms find that’s where the simple decision-making stops.
Even while more efficient codecs come to market, Facebook, Google, Tencent Cloud, and Netflix need to ensure they don’t lose a single viewer by side-lining an older standard.
“We can’t just deploy every new codec,” says Anne Aaron, director of encoding technologies at Netflix. “If a TV at home only supports H.264 we have to continue support for it.”
“There is no way a Facebook member can’t watch video just because we choose to end a codec,” says Ioannis Katsavounidis, part of the Video Infrastructure team at Facebook. “Deprecation is a big issue and getting bigger. Every new codec we add to hardware is increasingly complex while the resolution we are asking each codec block to decode is getting higher. As an industry we may have to think about what the end-game for a codec actually is.”
The issue is that MPEG4 AVC is the most-installed codec worldwide by saome margin. As more efficient schemes like HEVC and AV1 wait in the wings, even the world’s largest streamers are cautious about adoption.
“The reality is that there are a lot more gains you can wring out of older versions [of the codec],” says Matt Frost, Google’s director of product management. “We stream a lot of content in VP9 for YouTube, streaming movies and Hangouts. VP9 is the real workhorse for us, but we also use a lot of H.264 while we wait for AV1 ecosystem rollout. We are looking at AV1 and other commercial solutions.”
Facebook’s current codecs boil down to AVC and VP9 for both live and VOD parts of its service. It is currently evaluating plans for AV1.
“Our tests show significant advantage when comes to live video use cases,” explained Katsavounidis. “On the VOD side we are still trying to understand its benefits. For the majority of content there could be a mix between the two.
He added, “By end of this year we ought to have good signal about deployment.”
Tencent’s standard is H.264 partially due to slow adoption of HEVC in China “because of licence problems,” said Yu Yang, technical director of live broadcasting for Tencent Cloud. “We do have HEVC working on larger resolutions and we’re working with some OTT providers with AV1 to provide 4K and 8K live streams over IPTV.”
The session was chaired and sponsored by Intel, which has developed a souped-up version of AV1.
Scalable Video Technology for AV1 (SVT-AV1) is available open source and royalty-free, and offers performance and scalability gains in video processing, particularly when optimised with Intel processors.
Without any live component, Netflix has already encoded part of its catalogue in AV1 but has yet to deploy it. Aaron said the streamer was using the spec from AOM but wants an alternative.
“We are the first to partner with Intel on the SVT-AV1 project,” she said. “We will probably deploy significantly by next year. The main limitation is the amount of devices that can currently play it. It has to play so the device support is very important.”
Facebook shared the same concern. “Decoder support is the driving force. The sooner hardware decoders for mobile devices become a reality the sooner it will accelerate our deployment of AV1. As devices come online with AV1 support we can turn them on.”
For Google “there has to be virtual ubiquity for a codec,” Frost said. “VP9 is our baseline codec on top of which we may introduce AV1, AV2, or whatever comes next. We have to know that that is everywhere because it takes a while for the hardware development cycle.”
Across the board, the motivation for introducing a new codec is to reduce bandwidth while delivering the same quality.
Yang said AV1 was giving Tencent clients with high resolution streaming needs a 30 to 50% bitrate saving. “If I continue to stick with H.264 then my business partner will ask me why,” he said. Tencent said it would deploy AV1 at scale in the second quarter 2020.
Another reason for a codec update is saving on computing power requirements.
“We have significant storage costs and significant encoding costs,” Frost said. “We need a codec that will allow us to encode faster, therefore reduce cost, at scale.”
Google’s cloud gaming service Stadia requires super-fast encoding, “faster even than SVT-AV1 on Intel. In that use case we may have to wait for optimised software to come along.”
Next generation codecs make headlines because they are designed to enable exotic applications like 8K streaming. That’s not where Facebook or Google’s business needs are.
“We’re focussed on the next billion users and it’s not going to be those watching 8K or VR,” Frost said, “It’s those people trying to video conference across the globe from Indonesia to the U.S. which is a target for us. It’s the low-end use cases we are most excited about.”
Facebook also sees low bitrates as important for real-time video conversations between people.
The Netflix executive added, “While some people are lucky enough to have unlimited data there are many others with pre-pay data plans. The great advantage of a next-gen codec is to enable people to watch more hours of Netflix for the same amount of data.”
Aaron also pointed out that H.264 is a “really good proven” codec whereas AV1 is promising. “AV1 is new. There are still kinks in implementation. New tools like film grain synthesis are not fully utilized. There’s a lot of potential, but neither the encoder nor decoder has matured yet.”
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