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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

#131

Post by ponker »

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+.

Most routers can log enough information to calculate the bit rate. You’ll need enterprise equipment to show a real time feed per MAC but getting a “total bytes transferred” now and an hour from now is very easy.

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

#132

Post by xzel »

snailmailman wrote: post #56
ProfessorLayton wrote: post #39

Earlier quoted context omitted.

I've noticed that ATV+ looks the best, which is much appreciated. However, what has been driving me insane with all these services is how the bitrate is completely inconsistent throughout, depending on network congestion. Every service I subscribe to will "automagically" lower the bitrate if the network can't handle it. Which is fine, I get it. The thing is, it's the only way to watch anything, and depending on the c…

On my phone it lets me download Apple TV+ content. The files are shockingly large compared to what Amazon Video downloads are. A 1 hr clip was maybe 800mb in prime, but a few gigabytes from apple. (I don’t have any on my phone atm, but a quick search is telling me episodes of “For all mankind” are ~4GB and an hour long) It looks noticeably better, a massive step up that is completely worth the extra bytes. On my desk…

There is a setting in Prime Video to download the highest bitrate which is often around 4GB for a 2 hour movie, iirc. Totally agree with you on the download in advance rentals. With good enough internet it makes the experience of rentals so much more enjoyable.

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

#133

Post by hinkley »

HenryKissinger wrote: post #3

ELI5? Edit: Why the downvotes?

You expect a video to play at exactly 1 second per second. But compression or network bandwidth can screw that up. What do you do?

Ages ago they solved this by making some frames more important than others. Key frames being the top priority. If you are falling behind you can drop everything you are working on and skip to the next key frame. Then they added other priority levels so you can dump part of the work instead of all of it when things are only a little choppy.

With a zip file if you don’t have the middle of the file you can’t figure out the end. So clearly video is doing something different if they can remove chunks and still work.

Many of our compression techniques for video “hang” off the key frames. All the pictures around them are described as a set of changes to the key frame. Much smaller, but also why your screen occasionally looks like a horror show. Something went wrong and the changes were shown using the wrong starting point.

If the key frame is right before the scene changes completely, then you will struggle to compress the transition. There’s not enough space to describe all the changes. But if you have a program look for the transitions, you can delay or advance the key frame a bit so it lands exactly on the camera change. Bang. New picture. Then everything looks right.

Today it’s gone a lot farther. There are hints and patterns that span a whole movie or a chunk of it that for instance clues in that the whole movie is shot in sepia tone or a dark cave so you can guess the next scene will be sepia too. They’re talking about lining those attributes up with big shifts in the camera work, like someone coming out of a cave into bright light.

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

#135

Post by motoboi »

throwawaythekey wrote: post #125
bscphil wrote: post #121

Earlier quoted context omitted.

> 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'

Safari on Mac OS Catalina is always h264

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

#136

Post by hinkley »

myself248 wrote: post #41
Groxx wrote: post #16

Earlier quoted context omitted.

Coarsely detecting cuts is relatively simple - look for large frame-to-frame differences (e.g. encode however -> find large frames surrounded by smaller ones -> done, it's as accurate as your perceptual compression is). There are a number of ffmpeg-using tools out there doing this and other "cut to / from black" detection and it's pretty good. Not good enough for a human to say "yeah, these are all scenes", but proba…

Seems to me that if the frame-to-frame difference isn't big enough to detect that way, it's not likely to benefit from a new I-frame, yeah?

Imagine if the compression for the movie “Hero” couldn’t exploit the color themes in each act of the movie. That would be a might bigger.

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

#137

Post by sxp »

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…

Netflix has a debug screen that will show you the codec info. It varies depending on platform but you can Google it to find the one for your platform. For the Windows app, it's Ctrl-Alt-Shift-D. That shows H264 on my device since I don't have hardware that can decode H265. On Android, I've seen VP9 streams.

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

#138

Post by moron4hire »

ponker wrote: post #127

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.”

Take a wild guess.

(it's digital rights management and "Woo, PCs are scary!")

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

#140

Post by saxonww »

rblatz wrote: post #82
arendtio wrote: post #12

Looks amazing and while I would like to enjoy such quality and am willing to pay for the premium plan (in fact I do already), I still can't watch the 4K content even in a world where I accept DRM modules in my browser, because some DRM plugins seem to be more equal than others.

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.

I don't have a TV, so if I watch Netflix it's in a browser.

Most people don't realize this but you can only watch Netflix in 4K in a browser if you're using Microsoft Edge on Windows or Safari in macOS 11. In fact, you can only get 1080p if you're running Chrome in Chrome OS, or IE, or Safari. All other browsers, including Chrome and FF on macOS, Linux, and Windows, are stuck at 720p.

Their blog post[0] from 2017 sounded hopeful for higher resolution video on Linux - they wrote "We... look forward to high-resolution video being available on more platforms soon" almost immediately after announcing FF on Linux was supported - but in hindsight it's clear that what they really meant was what you point out - support for things like Apple TV, Xbox, and TV Smart Apps.

[0]: https://netflixtechblog.com/update-on-html5-video-for-netfli...

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