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SME '19: Twitch's Tarek Amara Talks Multi-Codec Streaming

Learn more about multiple-codec content delivery at Streaming Media's next event.

Read the complete transcript of this interview:

Tim Siglin: Welcome back to Streaming Media East 2019. I'm Tim Siglin, Contributing Editor with Streaming Media magazine and the founding executive director of not for profit Help Me! Stream. And today I'm honored to have with me Tarek Amara of Twitch. What's your title now at Twitch?

Tarek Amara: I'm now a Principal Video Specialist at Twitch. And my focus is mainly our video transcoding platform. So I'm part of the transcoding team, and our main focus is to deliver best video quality, best cost, best quality as well and new services. So anything wrong the encoding falls to our team.

Tim Siglin: When we talked during Streaming Media West, you were in the process of doing the implementation of VP9. And then, as I understand, you actually did a presentation today where you talked about the learnings that came out of that. Tell me a little bit about what, first of all why multiple codecs, and then secondly what have you learned?

Tarek Amara: I just finished the presentation with my colleagues about multiple codecs at Twitch, And the multiple codec is really to answer three questions. Lower bit rates, lower cost, better video quality eventually, alternative. Deploying new technology such as 4K HDR, 8K coming, and watching demos at NAB. And the third reason is probably reaching more people. If you have lower bit rate you can always go to different regions of the world and people with low bandwidth will have better services. AVC, at the moment, doesn't answer all these points. And we need new technology. However, as well, the other challenge is there is no codec that is replacing AVC. So what we need to do is we need to add to AVC new codecs, and that's why we start investigating what to deploy, and we came up with the decision that VP9 is the way to go.

Tim Siglin: So it's not necessarily you're coming in to replace AVC or H.264; you want to have two codecs in parallel doing what each one does best.

Tarek Amara: Exactly. First of all, I'd like to mention that with the changes we're making, we're making Twitch a multi-codec platform. I really want the message to go, Twitch is not adding VP9. Even within our teams, the message or the way we are approaching this think about a new codec coming in in the future. AV1 could be our next codec.

Tim Siglin: And I think one of the things you said to me at West was it was really sort of a rethinking of the whole model, because when you'd been single codec-focused, it doesn't matter what the second codec is, and then it could be "n" codecs, but ultimately you have to rethink everything and how you do your infrastructure.

Tarek Amara: That's exactly the point. So imagine we have one channel, all we need to change at some point and hopefully we can deliver this is: this channel, based on lots of business logic we cannot say it will get VP9, AVC, and HEVC or whatever. And bank on the system will take care of that and will deliver the signal in three different formats. And the players will decide who gets which format based on the business analysis.

Tim Siglin: Got it. And if I remember correctly, when you were on my panel yesterday where we talked about preparing for a multiple-codec world, you said that VP9, at the moment, the approach for 1080p60 is still AVC, and VP9 is everything except 1080p60?

Tarek Amara: Today, if you look at our AVC stack, it goes 1080p60, and the multiples of resolution underneath from 720p60 all the way down to 160p. For VP9, we're doing exactly the parallel. So we would like our customers who are going to be watching VP9 to have the same experience. So we're delivering completely two parallel patterns with priority to VP9-whoever can watch VP9-- because that will be either better quality or lower bandwidth. Whoever cannot watch VP9 is going to revert back to AVC. And the player is kind of helping our system making the decision. So, I'll tell you this, actually. The player is the one checking, is the platform VP9-capable? And if it is capable, it will go and request a VP9 from our back end.

Tim Siglin: Got it. So it's almost like the HTML5 video tags where, whatever your browser defaulted to, that's what you would have, and then it would fall down to the next one or the next one.

Tarek Amara: It's a similar logic build within our player, because we have our own player as well. And we're going to deploy VP9 for people watching Twitch on our old player.

Tim Siglin: Okay, interesting. And what about AV1, because I know there's a lot of discussion around AV1? Does doing VP9 now as your second codec help you sort of move toward easier implementation of AV1?

Tarek Amara: I think that's exactly a very strong point of us moving to VP9. First of all, adding AV1 would be very straightforward. Even if you look at the interface between libaom versus libvpx. There are lots of commonalities. So then integration would be easy, but also, since now we are robustly and confident we are multi-codec, AV1 is definitely a very big star in our roadmap. So we're trying to see how it is deployed from a platform support point of view, and then also we're trying to see who's doing realtime encode. Our challenge--contrary to the challenge of VOD providers--is realtime encoding with the gains of the encoder itself.

Tim Siglin: And for those engineers who had been focused on AVC, what was the biggest mental shift in moving to a multi-codec workflow?

Tarek Amara: It's in different levels. So imagine one system that was built around AVC, so lots of things are AVC-aware. Let me give you a small example. For example, one way for us to signal to our viewers when the channel goes live is, we send a notification to our viewers that this channel is there. And that is coming from the AV1 encoder started running. Now we have two encoders running, so is it the AVC that still sends a notification, or should it come from a high-level system to notify our viewers that we have channel, whether it is VP9 or AVC doesn't matter.

Tim Siglin: And if there's something that's going out in VP9, do you let people who can only watch AVC or vice versa?

Tarek Amara: The current decision which was discussed in the previous presentation is to make AVC because everyone can watch AVC. So if once we send the notification, if someone who's VP9-capable is watching on a platform capable--

Tim Siglin: It launches the player and transfers it, then it will make the response for VP9.

Tarek Amara: And we will end up delivering for VP9.

Tim Siglin: So that is interesting about the higher-level notification because ultimately at that point, the system has to be aware of the AVC encoders, the VP9 encoders et cetera.

Tarek Amara: It's definitely outside the AVC path or the AVC codec implementation, so it's no different layer completely.

Tim Siglin: It's the meta-workflow as opposed to the workflow itself. Interesting. All right, VP9 is fully launched at this point or it's in its final stages of beta?

Tarek Amara: It's actually going to have stuff beta which is for Twitch stuff this month, and we're hoping before end of this quarter we're going to have few channels and to present VP9 to all public.

Tim Siglin: Okay. So we will definitely pay attention to that here at Streaming Media and probably when that goes live, whether it's soft launch or a full launch, we'll do some coverage on that.

Tarek Amara: That would be cool. We've been working on this for a year-plus, very exciting. But again, we looked at this from changing lots of our infrastructure not just plugging in a VP9 encoder. So we are excited to see this coming to a fruitful delivery.

Tim Siglin: Awesome, Tarek, thank you very much.

Tarek Amara: Thank you very much.

Tim Siglin: And we'll be right back.

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