[Mplayer-dev-eng] libavcodec speed

[Arpi]

Hi,

Just made some tricky benchmarks to check what is still slow in it.
I have really fast system now (today upgraded to celeron2-800 at 1066, 133mhz fsb)
but it's still not fast enough. I thought it's memory bandwith/speed
problem, but how divx4 solves it then?

Now, here are some results.
I tested 3 variants, 1 with full divx decoding (perfect picture), 1 with
disbaled motion compensation code (buggy shit :)) and oen with disabled dct
too (parsing only -> empty picture)

File:  /3d/divx/sample.light.it.up.avi
VIDEO:  [DIV3]  640x352  24bpp  23.98 fps  823.5 kbps (100.5 kbyte/s)
full      : 10.272s 10.290s 10.257s
no MC     : 8.087s 8.083s 8.090s     =>  78.7%
no MC+DCT : 3.322s 3.327s 3.314s     =>  32.34%
MC: 21.3%  DCT: 46.4%  PARSER: 32.3%

File:  /3d/divx/405divx_sm_v2[1].avi
VIDEO:  [DIV3]  356x240  24bpp  30.00 fps  343.0 kbps (41.9 kbyte/s)
full      : 10.208s 10.129s 10.137s
no MC     : 7.485s 7.461s 7.493s     => 73.8%
no MC+DCT : 3.972s 3.988s 3.980s     => 39.25%
MC: 26.2%  DCT: 34.55%  PARSER: 39.25%

File:  /3d/divx/Coyote.Ugly.Sample-highbitrate-atmos.avi
VIDEO:  [DIV3]  640x480  24bpp  25.00 fps  1867.1 kbps (227.9 kbyte/s)
full      : 15.425s 15.409s 15.312s
no MC     : 13.056s 13.065s 13.029s  => 84.8%
no MC+DCT : 5.731s 5.759s 5.774s     => 37.3%
MC: 15.2%  DCT: 47.5%  PARSER: 37.3%

As you can see, MC (the biggest unaligned memory user) uses the
less cpu time. DCT is too slow, and parser is slow too.
I think parser can be faster if compiled with intel c compiler, or
optimizing at high-level just like i did with opendivx's postprocess.c.
I think parser should be much faster than now. Maybe we should add
some inline assembly getbit functions.
But why is DCT so slow? Is it so hard to calculate? Or is it unoptimized?

What about using 'prefetch' instruction? It could help at some point.


A'rpi / Astral & ESP-team

--
mailto:arpi at thot.banki.hu
http://esp-team.scene.hu

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