[MPlayer-users] speaking of vo... (was How I take a screenshot ??)

[Jan Knutar]

On Saturday 21 August 2004 23:25, ivanova wrote:

> > Advantages:
> > - source image is usually YV12 (like mpeg video), that's 12bit/pixel  
> > compared to 24bit/pixel fior RGB, so you need less memory bandwidth
> > - colorspace conversion (computationally expensive) is performed in  
> > hardware.

Also does hardware scaling for you, which is also computationally expensive
to do for mplayer, and it increases bandwidth requriements, for for example
-vo x11 fullscreen alot...

> Thanks, that really clears things up. ;)
> Where does xvidix and gl/gl2 fit into this?

Xv uses the drivers that XFree / X.Org provides through X. xvidix sort of
bypasses X and talks to the hardware directly, this provides some marginal
performance improvement.

gl/gl2 uses OpenGL, a 3D graphics API. This usually requires colourspace
conversion too, depending on the card, but most cards will be able to scale
in hardware. In most cards, the 3D engine is separate from the YUV overlay
engine, so you'll be using a different part of your graphics card with gl.

On my matrox card, the gl speed isn't really usable though :-\

> I also see a xover mode, I assume it 
> is just a generic version of xv.

I think some direct hardware drivers, like tdfx_vid, uses it... 

> Also, what is the difference between DGA and framebuffer?

DGA is direct access to an RGB framebuffer managed by X.
Might be marginally faster than x11. No hardware acceleration.

Framebuffer is direct access to RGB memory of graphics card,
and is managed by Linux kernel itself (in case of Linux anyway).
No hardware acceleration.
Advantage: You don't need X installed.