Video: Is 4K Quality Worth the Higher Data Rate?
UltraHD/4K streaming--whether in the gaming, other entertainment, sports, or enterprise space--is all about the experience, according to Twitch's Tarek Amara, and with 4K more than ever, you can't deliver a good experience without top-notch compression. At what point do delivery data rate limitations start to limit the quality of the experience, and what is the threshold where delivering HD well becomes preferable to delivering 4K badly? Amara explores these issues and more in this clip from his Streaming Media West presentation
Read the complete transcript of this clip:
Tarek Amara: The key to delivering media is compression. If today we had a magic codec that could do anything at 1 Megabit per second, we wouldn't be here; we wouldn't even be talking about compression. The way compression has evolved as we moved from SD to HD and now HD to 4K is about how compression has progressed versus how data has increased. As the data increased by 60 times, compression, from MPEG-2 days to H.264 days, improved by a factor of 50% reduction. Now we have a mature codecs, VP9 and HEVC, which improved compression by another 50%. Then there is AV1, which is futuristic, and probably trying to achieve another 50%. So where compression has become 400% more efficient, media has increased by 60 times.
Here we can ask the question, is it really worth it? I know there are a lot of skeptics--people say, "Okay, 4K TVs, I see nothing." You go to buy a TV at the store and you watch it a little bit and a guy tries to sell it to you and it looks great. You take it home, you watch a couple of live streams and say, "Rubbish, that's not good," and you're not enjoying the experience.
4K is great only as long as it is delivered correctly. So if you try 4K and really smash it to have the biggest resolution, the high frame rate, you don't encode it efficiently, you don't deliver it efficiently, you're ruining the experience.
Video quality is key in lots of markets. There are markets where quality doesn't really matter, but there are markets where people try to enjoy the experience, especially with a new technology.
Let’s say I'm a businessman who wants to launch my own 4K content. First of all, I study my bandwidth. I study my customers. I make sure my content looks great. But I also make sure which bitrates really suit my content. At Twitch, our content is gaming. Gaming is super challenging in terms of we need to provide 10-bit, the 60 frames per second, but also it's not camera-generated content. It's a content that could be rendered, that could have lots of artifacts which will make it an even harder job for the encoder to generate a good bit stream at lower bitrate.
So I’ll dedicate one slack for my UltraHD delivery and another slack for my HD, because you should not forget that this is a transition rather than just a black and white. You have content today that is generated in 4K. You are to deliver the same content for people who have small devices today who have older technology--H.264, which 90-99% of the market still uses.
To start your Ultra HD content you need to start a completely different slack, transcode everything in HEVC because you cannot find a device that can for 4K and probably something above 1440 will decode HEVC. As soon as your bandwidth goes slow and you move to 1080p to move to H.264 decoders. That's not very well-defined or available right now with the market. Switching codecs on a live event does not happen. Although it's something that people are working on, it doesn't exist right now.
And also try to make sure your bitrate goes great. Do not deliver UltraHD if you're going to deliver bad quality. There is no point. Probably go 1440p. You can encode it but encode it at the high bitrate. Don't worry about whether your customer is going to see it today or not. Some might, in the future they will, but do not go your UltraHD content, encode it at 15 Megabits per second for life, make it look rubbish, make it 1080p, make 1080p look even better than it does, and then you lose your customers, because UltraHD and what all high-bitrate video is about the experience.
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