[XviD-devel] Performance questions

Dark Sylinc dark_sylinc at yahoo.com.ar
Sat Aug 25 01:37:30 CEST 2007


I'm no XviD expert, but you're using OGRE, so I can
answer some questions

> > 1.  Is the result fps reasonable? I expected
> faster frame rate.

You're decoding a very big file (1024x768) which is
not largely used. Usually files are around 800x350 on
high quality. 47 fps is very fast, considering most
videos run at 23 fps; 30 fps for really smooth
playback (but games use to run at 60 fps)
You're dropping from 47 to 23 because 1024x768 is not
GPU-friendly. Use power of 2 resolutions, like 512x512
or 1024x512. OGRE probably converts it to 1024x1024.
If it doesn't (modern GPUs support non-power-of-2)
you'll still suffer performance hits. Also look if
you're creating the video buffer with dynamic write
flag set (HBU_DYNAMIC_WRITE_ONLY_DISCARDABLE).
XviD uses the CPU, games mostly use the GPU, that's
why it's so slow. Also take in mind that OGRE uses a
lot of CPU (but efficiently for most games). The Debug
version is also painfully slow.
As far as I remember, only a couple of games makes
intensive use of videos and polygons (Final Fantasy
and Grim Fandango) but note that polygons get reduced
when videos are enabled and vice vesa

> > 3.  Why MMX, MMXEX, SSE, SSE2 perforamce are all
> the same?

This will vary among vendors. Pentium III SSE is
faster than anything else, but on AMD Sempron enabling
SSE won't do anything great, although 3DNow! will work
reaaaly fast (faster than SSE).

Hope this help
Dark Sylinc


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