Jerky playback

[Gildas Bazin]

On Tuesday 10 July 2001 2:56 pm, Chris Jensen wrote:
>
> Do you mean hardware acceleration for decoding mpeg or displaying? I'm
> certain it can for the later (although I have yet to get xvideo working),
> and I would assume the former also since using --overlay did improve
> performance slightly.
> 

VLC doesn't use hardware acceleration for mpeg decoding as everything is done 
in software. Well, maybe you can argue that using the ac3 spdif output is 
equivalent to using hardware acceleration because the ac3 audio is then not 
decoded by VLC but by your ampifier (becareful, you need an ac3 amplifier 
with an spdif input).
But VLC can make use of hardware acceleration for the video output. For 
exemple, the Xvideo output plugin will use an YUV hardware overlay. That 
means the decoded MPEG pictures which are in YUV video format won't have to 
be converted to RGB in software, this step is done directly by the graphics 
card. And I think Xvideo can also use hardware rescaling with interpolation. 
So you will gain a lot using Xvideo.

Another thing: I looked at the code, and it seems to me that the --overlay 
option is not used anywhere (It must have been used in the past but is not 
anymore). Well it is referenced once in the SDL output plugin, but it doesn't 
do anything.
So --overlay shouldn't make any difference.

> > On the other hand it looks like you are missing one vital other library,
> like
> > svgalib (I use svgalib-1.4.1-13.i386.rpm) or another. I can't remember
> exactly
> > which libraries you need.
> 
> I'd say this is definately the problem as I had no idea i had to install it.
> Will I need to recompile vlc or anything else to take advantage of svgalib
> once it's installed? (ie xfree, or the xvideo component?)
> Where can I find out what other libraries I need (since I have probably not
> installed them).

I really don't think you need svgalib. All you should need for the Xvideo 
output is XFree 4.x.x and its development packages (for the header files and 
other things ...)

Also, If the SDL output and the Xvideo output are segfaulting on your 
computer but the x11 output is working fine, that would be a proof in favour 
of an Xvideo problem on your computer. Because, as you were guessing, libSDL 
is not a low level display driver, its goal is just to provide a consistent 
API to access the video display on several platforms (this is why vlc's SDL 
output plugin is working on Linux, Beos, Windows ...). And therefore it will 
try to use the best display driver available on your computer, which in your 
case will be Xvideo.
If you want to make sure that Xvideo is working on your computer, try to find 
another app that can use it.

You can also try to use GDB with vlc to trace this segfault ;-) 

--
Gildas