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Netflix is now doing per-shot encoding for UHD content

netflixtechblog.com

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Re: Netflix is now doing per-shot encoding for UHD content

#121

Post by bscphil »

zbobet2012 wrote: post #119
bscphil wrote: post #110

Earlier quoted context omitted.

> No they have not made it worse. 1080p encoded at lower bitrate can look better than 720p at a higher bitrate. Or vice versa. Even to the trained eye. It depends on the scene dynamics.* Well, of course that's correct. Take 1080p encoded at 100 Mbps and 720 encoded at 300 Mbps, I guarantee you that 1080p wins every time. :-) > In the ladders they posted (called a RD chart) we can clearly see they have made a better s…

> Reread my original post carefully - my point is that if you're stuck with 1080p as the maximum resolution, than the quality you can get with the revised ladder is strictly worse, because Netflix will want to jump up to UHD resolutions, but your device won't support it. These are for their HEVC encodes. Apple (and most others) require H264 to have a separate ladder which will be 1080p limited and will be generated o…

> These are for their HEVC encodes.

Really? I wasn't aware Netflix even offered anything other than H.264 at > VMAF does correlate pretty tightly with subjective metrics. This is a very detailed subject, I summed up many of my thoughts on the differences in my demuxed talk last year here: https://www.youtube.com/watch?v=nCUsXhSPyyw

Thanks, I'll check that out when I have the time. I'd still emphasize that it's quite possible for objective metrics to be fooled (that's why codecs have psy tunings!), and I do prefer several "old-ladder" images over the newer versions in Netflix comparisons here. I suppose I've become rather cynical about claims made on the basis of metrics ("now 50% less bitrate for the same quality!"), when to my eye, web video has always been very bad and is getting worse as companies keep reducing the bitrate.

Re: Netflix is now doing per-shot encoding for UHD content

#122

Post by bscphil »

zbobet2012 wrote: post #120
bscphil wrote: post #114

Earlier quoted context omitted.

> x264 will not align keyframes across resolutions and encodes. In addition the pershot encodes optimize more than just idr frame placement. They also optimize other encoder parameters such as aq. Sure, that's true. (Though I don't know why it matters that keyframes aren't aligned.) But at the end of the day the point is that Netflix has a better rate control algorithm, and this could be built into x264, even if it m…

> Sure, that's true. (Though I don't know why it matters that keyframes aren't aligned.) But at the end of the day the point is that Netflix has a better rate control algorithm, and this could be built into x264, even if it might require a significant amount of work. (Which I'm sure the x264 developers would be willing to do for a substantial quality improvement.) You can't ABR adapt without aligned GOP boundaries. >…

> You can't ABR adapt without aligned GOP boundaries.

Yes, that's true of course, but not really relevant to whether you could port Netflix's work on scene-adaptive rate control to x264. Maybe you'd lose aligned GOPs... but for a lot of purposes (offline?) that doesn't matter.

> Of course not, that's why the perform an analysis of both options and select the better one. That's what the algorithm does...

The only point I've ever tried to make on this subject is that in some cases this approach fails. "Perform an analysis" is such a high level description that it misses the fact that this is being done according to some objective metric that may disagree with an individual viewer's personal preferences or viewing environment. In fact, just because an objective metric says 4k > 1080p doesn't mean the difference will be noticeable at the viewing distance the viewer is at, whereas the additional artifacts introduced by moving from 1080 -> 4k without a significant bitrate increase may very well be visible!

Re: Netflix is now doing per-shot encoding for UHD content

#123

Post by pedrocr »

And if they would start providing 4K or at least 1080p to Linux users I might consider subscribing again. Streaming services are popping up left and right while at the same time turning into their own specific guettos of supported platforms and features. Makes you almost value the role of the traditional network aggregator. Maybe the market will eventually consolidate or organize itself so you can buy a full service from a single provider that knows what it's doing technically.

Re: Netflix is now doing per-shot encoding for UHD content

#124

Post by rblatz »

gruez wrote: post #106
rblatz wrote: post #82

Earlier quoted context omitted.

I am shocked at how many people watch Netflix in their browser. I have multiple different ways (AppleTV, Xbox, TV Smart App) to watch Netflix on my tv, and at least 2 of them support 4k.

It's not too surprising. Media players (chromecast, appletv, etc.) seem pointless if you already have a laptop and you're not too into movies/tv. Not everyone owns a game console, either because they don't game or they play on PC. Finally, some people (especially hn users) think that smart tvs are a privacy/security nightmare, so use them as dumb tvs.

I agree on the smart tv thing, I don’t use it, but it’s available. But even with numerous laptops and desktops I’m just not very likely to watch on one. It’s harder to watch with my wife or friends on a laptop, or desktop. And even though I have a nice setup I don’t want to sit in my desk chair all night after sitting in it all day. Im more likely to watch on a tablet while laying in bed or on the couch than an actual computer. But still use the Apple TV 90%+ of the time.

Re: Netflix is now doing per-shot encoding for UHD content

#125

Post by throwawaythekey »

bscphil wrote: post #121
zbobet2012 wrote: post #119

Earlier quoted context omitted.

> Reread my original post carefully - my point is that if you're stuck with 1080p as the maximum resolution, than the quality you can get with the revised ladder is strictly worse, because Netflix will want to jump up to UHD resolutions, but your device won't support it. These are for their HEVC encodes. Apple (and most others) require H264 to have a separate ladder which will be 1080p limited and will be generated o…

> These are for their HEVC encodes. Really? I wasn't aware Netflix even offered anything other than H.264 at > VMAF does correlate pretty tightly with subjective metrics. This is a very detailed subject, I summed up many of my thoughts on the differences in my demuxed talk last year here: https://www.youtube.com/watch?v=nCUsXhSPyyw Thanks, I'll check that out when I have the time. I'd still emphasize that it's quite…

Youtube mostly uses vp9 these days (I think it might fallback to h264 depending on the device?)

You can confirm this by loading a video, right clicking somewhere in the player and opening 'stats for nerds'

Re: Netflix is now doing per-shot encoding for UHD content

#126

Post by radley »

bscphil wrote: post #117
radley wrote: post #20

> Sometimes we ingest a title that would need more bits at the highest end of the quality spectrum — even higher than the 16 Mbps limit of the fixed-bitrate ladder. From just a cursory inspection using my Apple TV 4K, 12 Mbps is their target bitrate but their ceiling was ~16 Mbps. That's still only a third of what AppleTV+ offers (36/48) and only 2/3 of Disney+ (18/24). Netflix is still higher than Prime Video (10/14…

> only a third of what AppleTV+ offers (36/48) and only 2/3 of Disney+ (18/24) I'm very suspicious of these numbers, I think they might be the maximum transient bitrate and not the average bitrate. Do you have an example of an AppleTV movie or show that actually has an average bitrate that high?

I didn't do anything fancy. I simply turned on the Developer overlay in my Apple TV 4K and played a few 4K movies (if available) in each service. The bitrates were consistent within each platform.

I was very surprised by Apple's numbers (and HBO), so I did some Googling to confirm.

Re: Netflix is now doing per-shot encoding for UHD content

#127

Post by ponker »

Any idea why none of these services supports queueing some movies you’d like to watch, downloading them in the middle of the night in astounding bitrates, and allowing you to watch on your TV? As far as I can tell only the mobile apps support this, not the “streaming boxes.”

Re: Netflix is now doing per-shot encoding for UHD content

#128

Post by ponker »

bscphil wrote: post #115
dmurray wrote: post #113

Earlier quoted context omitted.

> My point is that if Netflix thinks they can do better, it would be great to see their code contributed to the public, since they're using an open source program to do all their encodes. This really is their core business and somewhere they can have a competitive edge, though. Even if you think it's unethical or that it might make business sense to contribute back to the upstream projects, you can see why they might…

Fair enough, I'm not arguing that they're obligated to or anything, I just think it would be nice. I do suspect that catalogue matters much more at this point than any tiny competitive advantage they get through better encoding. And they've certainly been willing to share advances (like VMAF) in the past - that's why this tech blog exists, after all!

Bandwidth is a huge cost for these services and if they share encoding techniques then their competitors can cut prices at the margins.

Re: Netflix is now doing per-shot encoding for UHD content

#129

Post by ponker »

ehsankia wrote: post #68
radley wrote: post #20

> Sometimes we ingest a title that would need more bits at the highest end of the quality spectrum — even higher than the 16 Mbps limit of the fixed-bitrate ladder. From just a cursory inspection using my Apple TV 4K, 12 Mbps is their target bitrate but their ceiling was ~16 Mbps. That's still only a third of what AppleTV+ offers (36/48) and only 2/3 of Disney+ (18/24). Netflix is still higher than Prime Video (10/14…

I'm assuming that when you're at as large of a scale as Netflix, if you were to provide bitrates like Apple does, it would probably collapse most of the internet backbone. I think Netflix and Youtube already use something like half of the internet's bandwidth. Now imagine if they just tripled that overnight. Though I guess there's a difference between allowing the user to switch to it vs making it default. Youtube lo…

Why not provide it for people who will pay for it? I know I would.

Re: Netflix is now doing per-shot encoding for UHD content

#130

Post by radley »

notJim wrote: post #31
radley wrote: post #20

> Sometimes we ingest a title that would need more bits at the highest end of the quality spectrum — even higher than the 16 Mbps limit of the fixed-bitrate ladder. From just a cursory inspection using my Apple TV 4K, 12 Mbps is their target bitrate but their ceiling was ~16 Mbps. That's still only a third of what AppleTV+ offers (36/48) and only 2/3 of Disney+ (18/24). Netflix is still higher than Prime Video (10/14…

> From just a cursory inspection using my Apple TV 4K I'm confused, how are you getting this information? Does Apple TV have a way to display the bitrate ceiling? Also, do you find the bitrate differences noticeable? On my 4k tv, I find Netflix looks pretty good, but Amazon looks pretty bad and HBO Now is awful of course (no Max yet, since I use a Roku.) This might be enough to get me to check out AppleTV+.

Apple TV has a Developer overlay with video metadata (requires XCode & dev account).

Yeah, there's a clear difference, especially on Disney & Apple. Apple is very close to 4K blu-ray (there's some YouTube vids comparing them).

I'm using a low end 4K projector, so it's more apparent.

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