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List:       freedesktop-xorg
Subject:    Re: XVideo question?
From:       Matthias Hopf <mhopf () suse ! de>
Date:       2004-11-24 15:29:08
Message-ID: 20041124152908.GA4833 () suse ! de
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On Nov 23, 04 09:47:02 -0800, Kendall Bennett wrote:
> So far with my testing of MPlayer and Xine, it appears that only end up 
> going into the drivers PutImage function, and don't seem to use the 
> offscreen video memory functions. This means that all video frames get 
> dumped to system memory first by the player, then copied from there to 
> video memory by the driver. This gets done for every frame. 
> 
> The offscreen functionality is clearly there to avoid this overhead, but 
> I can't yet figure out which applications will make use of this (nor what 
> client level API functions are used so I can code my own tested).

Video players usually have to build up the final image before displaying
it.  This typically involves read/write cycles that do not work well
with AGP or framebuffer memory. For example, the overlay images have to
be blended into the final image for DVD menus.

Thus they always have to work on their own copy. At least the xv driver
of xine tries to avoid copying image data before using PutImage(). This
function can be optimized (thinking about cache-lines, alignment, and
write-behind strategies) without xine being involved.

CU

Matthias

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