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Old 14th May 2014, 11:42   #19  |  Link
mandarinka
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Quote:
Originally Posted by Nintendo Maniac 64 View Post
EDIT 3: Did some new tests and I found something interesting. My HTPC has a 2GHz Conroe-based Core 2 Duo and in everything else seems to perform extremely similarly to my 2.5GHz Brisbane...except in this. If I watch a VP9 video through Chrome then the CPU usage is pretty much the same as it is on my Brisbane, but if I watch the video through MPC-HC (64bit) then the CPU usage is cut in half! This means that even 1080p 30fps VP9 is "only" using around 50-60% CPU utilization. My theory is that MPC-HC's VP9 decoder is taking advantage of SSSE3 which is something my Brisbane lacks, and therefore Chrome most likely just isn't using SSSE3. I'll be able to test this theory more-so when I get my sister's soon-to-be old laptop in 2 weeks since it has a 1.6GHz Core Duo (not Core 2 Duo) which also supports SSSE3 but has IPC only on level with my Brisbane.
Yes, SSSE3 is very useful extension and lately, people have starting to write assemly optimizations that require it (same situation in x265 I think). Hence the K8 (but K10 too) chips are out of luck since they only have SSE2 and are forced to run unoptimized C codepath.

But more importantly, all the assembly optimizations in ffmpeg's VP9 decoder are only written for 64bit mode. 32bit mode is IIRC unoptimised, because the author doesn't care about 32bit mode. If your Chrome is 32bit, then it doesn't utilise SIMD, but 64bit MPC does.

Quote:
Originally Posted by Ronald S. Bultje
Some users may find that ffvp9 is a lot slower than advertised on 32bit; this is correct, most of our SIMD only works on 64bit machines. If you have 32bit software, port it to 64bit. Can’t port it? Ditch it. Nobody owns 32bit x86 hardware anymore these days.
Quite a misconception, but alas, that's how it is. On the other way, who cares about VP9, really. It would be a problem if they acted the same way about HEVC.

Last edited by mandarinka; 14th May 2014 at 11:46.
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