vout 4 performance issues

Samuel Hocevar sam at zoy.org
Fri Jun 8 05:52:55 CEST 2001

   I'm kinda stuck with my vout 4 development. It was supposed to
be faster due to the video being decoded directly into the overlay
surfaces, and I had benchmarked such improvements, but now that the
performance problems have been fixed in current CVS, vout 4 is slower
than current CVS (even after applying the same fix, of course).

   Here are the figures on my computer (average values on 5 tests,
Pentium III 650, 256KB cache, Dolby_Broadway stream):

   released vlc 0.2.80, -A dsp, -V sdl  : 62% cpu (X: 20% cpu)
   CVS vlc 0.2.80, -A dsp, -V sdl       : 51% cpu (X: 20% cpu)
   vout4 vlc 0.2.80, -A dsp, -V sdl     : 54% cpu (X: 1% cpu)
   CVS vlc 0.2.80, -A dsp, -V dummy     : 38% cpu
   vout4 vlc 0.2.80, -A dsp, -V dummy   : 43% cpu

   As you can see, vout 4 vlc is really slower, even in dummy mode,
which I fail to explain. The speed loss in SDL overlay mode is smaller
but that's probably because X already eats a lot less CPU with vout 4.

   Actually I'm beginning to think I left a huge bug somewhere in
the code. Any ideas on how to track this problem? Is there anyone
with efficient profiling tools on his platform? AFAIK, Linux lacks a
multithreaded profiler.

   Tarballs can be found here for comparison (cvs == today's CVS):



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