[mythtv-users] Xv and XvMC - what's the difference?

[Joseph A. Caputo]

On Thursday 08 January 2004 16:46, Emlyn.Bolton at nokia.com wrote:
> Hi,
> 
> Could somebody enlighten me as to what Xv and XvMC are exactly, and whether 
my assumptions are accurate.
> 
> I assume that Xv provides some form of direct access to the screen but I'm 
unsure of the specifics.  
> 
> Thanks in advance!

Xv is X-Video.  It's a standard API/protocol/whatever for using video hardware 
to accelerate certain operations.  Myth uses it primarily for scaling (so 
that you can have full-screen video, regardless of the recorded resolutoin) 
and contrast/color/brightness output controls.

XvMC is X-Video Motion Compensation.  It's basically an interface to 
hardware-accelerated MPEG1/2 decoding.  I don't know much about MPEG 
decoding, but my understanding is that it only does iDict, which is only the 
first stage of the decoding process, not the full decode like the PVR-350 
does.  Somebody who knows more can probably give a better explanation.  At 
the moment, the only available XvMC implementation seems to be the binary 
Nvidia driver for the GeForce4 MX or GeForce FX cards.

-JAC