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Old 20th October 2017, 19:46   #15  |  Link
benwaggoner
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Join Date: Jan 2006
Location: Portland, OR
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Quote:
Originally Posted by pandy View Post
But when we compare x264 and x265 then increasing complexity of the JET looks quite unpleasant... I know that overall trend is to use more threads but still - increasing computational complexity (exponentially) quickly become serious issue.
Those 64x and 16x are just worse case scenario a bit exaggerated figures.
The real comparison should be quality at equal perf. If a codec offers a 100% improvement at 64x encoding time, but a 50% improvement at the same encoding time, it's still a big win. I doubt anyone is doing HEVC with the same coverage of theoretical options as they do with H.264, but HEVC still delivers some big real-world efficiency improvements at practical speeds.

These theoretical encoding times are really JM versus HM; encoders which are far too slow for any practical use, and really not very good psychovisually. And for decoder complexity, that's what Profiles and Levels are for. If there is a 16x worst case, probably 85% of the practical efficiency gains can be found in the first 2x of decoder complexity. Hitting the right balance between efficiency gains and decoder complexity is a huge part of designing a major bitstream format, and one of the reasons that the MPEG/ITU codecs are so good. There are just so many eyeballs from so many different industry sectors pounding on it to squeeze every last bit and MIPS out.

Quote:
In 80 when MPEG-1 (and later 2) was born every 2 - 3 years CPU computational power was almost doubled, now we observe severe stagnation on this - rarely new CPU's are providing more than 20% processing gain...
Per core and for general compute, perhaps. But whenever a chip is "5-40%" faster, video encoding is the 40%. Because we can go widely parallel, and use SIMD instructions like AVX2 harder than about anything. And the good implementations get so much hand-tuned assembly optimizations.

The new 8th gen Core processors look to offer ~2x encoding throughput per dollar and per watt. More cores, less thermal throttling using AVX/AVX2, microarchitectural improvements, and hopefully some value in AVX512.

This is a bigger leap than most generations, but a slowdown in Moore's law will hit video the least and latest of almost technology.
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