SME 2018: IBM Cloud Video's Scott Grizzle Talks Protocols, Codecs, and Latency
Learn more about latency and streaming delivery at Streaming Media's next event.
Read the complete transcript of this interview:
Tim Siglin: Welcome back to Streaming Media East 2018. This is the last interview of the first day. I'm Tim Siglin, Contributing Editor with Streaming Media Magazine, and the Founding Executive Director of the not-for-profit Help Me! Stream. I've got Scott Grizzle, Senior Solutions Engineer for IBM Cloud Video, here with me today. You did two sessions today, one on unified communication, and what was the other one?
Scott Grizzle: Low-latency streaming.
Tim Siglin: Okay. What does low latency mean to you? Because there are so many definitions.
Scott Grizzle: That's what came up, and I talked about the difference between what is latency and what is delay. Also, what is perceived latency and versus actual latency? If someone's in the room watching us stream, they'll perceive latency. If they're at home, watching this, like right now, you're not perceiving the latency.
Tim Siglin: Right, because there's nothing to compare it to.
Scott Grizzle: That's a big thing is, and it can do a lot for us. Industry average for latency, with HLS, is anywhere from 15-30 seconds. Now, you tell somebody that, and he goes, "That's a long time." Not really. Can you reduce it? Yes, but you're also giving up scalability and reliability. So, that's why that delay is built in--it’s so the actual stream will be delivered well, and you can handle massive scale.
Tim Siglin: So, that three-legged stool of get it there fast, get it there accurately, get it there at scale--where do you sort of fall in that model?
Scott Grizzle: Our biggest thing is the highest quality stream, and a guaranteed stream. We actually use multiple CDNs for delivery. So, we have our own, plus we use Akamai, and you know the big ones out there. That may make you think we'd be worse than the industry average. We're actually not. We're on the lower side. Industry average is about 15-30 seconds, depending on what type of device you're watching on, because it depends on how you connect with your local ISP. Your connectivity always depends on your local ISP, because that's going to determine your end mile, how you're going to watch, versus getting pulled from a CDN.
That's where some of the confusion gets out. When I say the delay is 30 seconds, sounds like a lot. When I actually say my latency is 45 milliseconds, that's complete repackaging and sending it out there, then it starts making sense. "Oh, that's what the delivery time is by delay." It always is.
Tim Siglin: Ultimately, we have multiple stages of delay or latency. The first is a group of pictures. If the group of pictures is two seconds long, you've essentially got that right there. Then, as you say, you've got the repackaging, whether it's for HLS or DASH, or what have you. Then you've got the actual moving it onto the network, the network transporting it itself. It coming back down to the last mile, dropping to the person, and then decoding.
Scott Grizzle: Exactly. We were kind of joking about RTMP, you know the long agonizing death of Flash. But RTMP actually can be low latency.
Tim Siglin: Very low latency.
Scott Grizzle: People forget that. And like the same with RTSP, and that's been “dead” for years. Not really. Major broadcasters use it, and they can get a couple-second latency with forward error correction.
Tim Siglin: I think that whole concept of dead is really difficult because Flash, while, it's been deprecated, it's definitely not dead. RTSP just fell out of favor, because RTMP provided a better solution at scale. RTMP, as you say, is still alive and well. In fact, it'll probably be another six to eight years before it's gone.
Scott Grizzle: That's exactly what I say. It's like RTSP, not dead, still around. MPEG-2, still around. I mean, will Flash ever go away? Don't know. There'll probably be encoders that will do it. You're not going to give away your Elemental tomorrow, because you've got to go with some other ingest. You're going to wait till that thing dies. So, how long are those codecs going to be around? You have to think of all the small guys, the licensing fees in RTMPs relatively cheap. So, most encoders will do that, so that means most ingest will be RTMP, or HLS, or some other format in.
Tim Siglin: On the contribution side, there may be some move to other things, but ultimately RTMP makes sense from the delivery side, because you can potentially scale it as well. I guess the last question on that is, DASH versus HLS. What do you all see in terms of requests for using DASH for delivery versus HLS?
Scott Grizzle: That came up in that session also. Right now, people forget about VC1. I know you're familiar with it. VC1 was very encoder-heavy, light decode, versus H.264. Now you're seeing the same thing with HLS and DASH. Right now DASH is a little more encoder-heavy, lighter on the decode. Not as extreme as the other ones. But you're seeing a faster delivery time on DASH right now. Also, they don't have the same chunking, or the same chunks as HLS has. HLS has, by default, three seconds of three chunks, so nine seconds right there.
Tim Siglin: And they were an ATM-based packet, so there was a lot of header information that's not needed as well.
Scott Grizzle: Exactly. Also, if you look at DASH, you have a lot more companies involved in DASH. Again, it's kind of like back to H.264 versus VC1. You have more people contributing. It takes longer to move than an HLS like Microsoft and Apple did, but they can do stuff fast. Also, if you're looking at DASH, how are you going to deliver your HEVC? How are you going to deliver your AV1? It's not going to be in HLS right now. Because right now everyone's talking about delivering via DASH. So, that's what you've got to look at, is it can handle the new codecs out there, which really when we see what Apple comes up with for HLS.
Tim Siglin: It's interesting that Apple responded by doing fragmented MP4. Now, you probably remember I wrote a white paper, co-written with Adobe and Microsoft. It was their first joint paper, arguing for fragmented MP4. Apple at that point was still looking at transport stream completely, but ultimately now they've come back to byte range and that kind of thing. Do you think Apple will respond to that delivery benefit of DASH by figuring out something on the HLS side, or do you think inherently they'd have to restructure the entire packaging solution? No pun intended.
Scott Grizzle: Don't know on that part, but I would see, if they are going to stick with Flash for a while, as I assume they will, I would not be surprised if they do the chunked up MP4s, and repackage those. It doesn't surprise me. Again, who knows? What does Apple have? There's going to be a new version of it like every iPhone, but again, they'll come out with something groundbreaking, totally different than we ever have seen before. It's like everybody hated those stupid EarPods, but now everybody has them though.
Tim Siglin: Right, very true. All right, Scott, as always, very enjoyable to talk to you. We'll be back tomorrow morning.
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