[8] Linux vs Windoze

[kevin at ank.com]

There are probably several factors.  Depending on the video card you
use, you may or may not have full acceleration support from XFree86.
Using a commercial X server like AcelleratedX would fix this if that
is the problem.  

Secondly, your CPU may not be well optimized under Linux; commercial 
compilers often generate executables with performance that is up to 
twice as good as GCC.  GCC is not optimized at all for the AMD Athlon, 
and only somewhat optimized for Pentium III and higher.  Instruction 
scheduling plays a huge role in how well exectuables perform on the 
most recent chips, so using a commercial compiler or some of the newer 
experimental open source compilers like PGCC, and AthlonGCC to compile 
vlc may help these problems.  

Lastly, using SDL isn't the best choice for rendering Video data.  X11
comes with many protocol extensions, some of which are better and some
worse at quickly rendering lots of bitmap data.  The core protocol is
quite poor, but using XFree86 4.0 you can instead use the XV extension 
if your graphics board is one of the ones for which an XVideo driver 
has been written.  For boards without XV support there are some tweaks
that you can do to speed up X11 by 10% or so, such as setting up the 
MTRR registers correctly.  

For what it is worth, vlc on my P-II 750 notebook is quite smooth without
any of the optimizations mentioned above.  My desktop is a 1.4GHz Athlon
that is mostly smooth with occasional hiccups with an XV supported 
video card (the GeForce3).

Cheers,
-kls

On Mon, Nov 26, 2001 at 09:55:25AM -0800, Doug Wolfgram wrote: 
> Now that I have vlc running on the same machine in both Windows 2000 and
> Linux (RH7.2) I was wondering if someone could explain why the Linux
> version is choppy and the video gets out of sync with the audio.
> 
> Is this the difference between SDL and DirectX? Is it correct to assume
> the same basic codec is used for both and that the video performance
> difference is in the video device drivers and such?
> 
> Any help would be enlightening. I'd like to stay on the Linux side, but
> the video doesn't play smoothly. 
> 
> D
> 
>  
> -- 
> 
> Doug Wolfgram
> Principal
> CTO Partners
> www.ctopartners.net
> partners.net
> 
> 

-- 
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