Netflix Encode Optimisation

muon

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muon

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Was reading this last week and thought others may be interested.

http://techblog.netflix.com/2015/12/per-title-encode-optimization.html

I wouldn't have thought to do this. Would have just done a fixed ladder.

For Maths nerds, the efficient frontier can be depicted as below.

2pzjgie.png
 
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They have some interesting stuff on their blogs, another one was discussing the % of the US internet bandwidth netflix uses (think it was some 40% at peak times) also performing the encoding so that the facial features had the best encode, plus the search for an alternative no royalty(non hevc) codec.

Seems a pity netflix are not yet pursuaded to give an offline/download service though, like the bbc&amazon.

The recent comments about the 5Mb/s bbc hd freesat&freeview 1080i broadcast of Planet Earth 2 (and other material) impacting quality are interesting, in the light of your netflix article, since maybe the 720p 6Mb/s iplayer download looks better. (indeed never bought the PE1 blu-ray but maybe that was required to do justice to the production)

Maybe I will eventualy watch some of pe2 but the netflix blog is more interesting.
 
Video codecs are funny things, that graph doesn't really surprise me much as it backs up what I've read from people who encode DVD's. Different types of content can get away with wildly varying bit rates, some animation can get 3-4 hours on a DVD and look good, whilst Criterion would cut out some audio tracks/extras to get the best PQ on a 2 hour film.
Even just different encoders at the same bit rate and the same settings can make a difference with the same content, or a minor change in the encoding.

Going back about 10-15 years there was a particular DVD authoring company that was used by some US anime publishers and you could often tell it was them rather than an "in house" or other company because they usually managed to get a better encoding/dvd.

The BBC tech blogs have had some interesting articles on it in the past, and from memory they mentioned that one of the changes in encoder made a big difference in the PQ for the same bit rate, it's one of the reasons they from memory use variable bit rates within the total they've got for all their channels, so if they've got an action movie on 1 and a quiz show on 2 then BBC 1 can use a higher bitrate for it's encoding.
 
Something else interesting now is Adaptive Bit Rate Optimisation although I don't think Netflix use it. Basically in an online stream you have several layers of different bit rates typically chunked into 10 second segments and the player picks the highest bit rate based on your bandwidth. What ABRO does is it strips out a higher bit rate chunk if a lower bit rate chunk is of the same perceived quality resulting in you and the service using less bandwidth.
 
Sirrel Squirrel said:
Something else interesting now is Adaptive Bit Rate Optimisation although I don't think Netflix use it. Basically in an online stream you have several layers of different bit rates typically chunked into 10 second segments and the player picks the highest bit rate based on your bandwidth. What ABRO does is it strips out a higher bit rate chunk if a lower bit rate chunk is of the same perceived quality resulting in you and the service using less bandwidth.
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http://techblog.netflix.com/2016/12/more-efficient-mobile-encodes-for.html

Using it for mobiles now. Kind of makes sense there as people care about data usage on mobiles.

Per-chunk encode optimization

In our parallel encoding pipeline, the video source is split up into a number of chunks, each of which is processed and encoded independently. For our AVCMain encodes, we analyze the video source complexity to select bitrates and resolutions optimized for that title. Whereas our AVCMain encodes use the same average bitrate for each chunk in a title, the mobile encodes optimize the bitrate for each individual chunk based on its complexity (in terms of motion, detail, film grain, texture, etc). This reduces quality fluctuations between the chunks and avoids over-allocating bits to chunks with less complex content.
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Another interesting netflix article about their likely adoption of vp9 changing from hevc found via netflix 4k info here

.... And then there's the browser: 4K streaming only works in Microsoft Edge, because it's the only browser that supports PlayReady DRM. Basically, streaming 4K Netflix on a PC requires a CPU that's in barely any devices right now (desktop chips aren't expected until sometime in 2017), the latest version of Windows 10, and using an unpopular browser, making it a largely useless feature.
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