[mythtv-users] Can't get XvMC compiled in MythTV

Daniel Kristjansson danielk at cuymedia.net
Thu Apr 19 02:20:51 UTC 2007


On Wed, 2007-04-18 at 19:14 -0600, Chad wrote:
> Hi Tom,
> 
> > Ok, I'm confused about XvMC still.  Do you have to have Nvidia drivers?  What
> > about openChrome for VIA EPIA?
> 
> XvMC is an implementation of the driver for a chip. Nvidia, Via (and
> maybe at some point in the future) and Intel have XvMC implemented (or
> have plans for in the future) in their Linux drivers.  Via does via
> (heh heh, I just wanted to do that...) the openchrome drivers, but
> AFAIK NOT through the Via provided drivers.

nVidia and Intel have both implemented MPEG-1 and MPEG-2
acceleration using the XvMC standard for a number of years.
The OpenChrome guys have not yet implemented either XvMC MC
or IDCT acceleration, i.e. the acceleration methods in the
standard. They have implemented something called VLD
acceleration, which works with most, but not all, MPEG-2
streams. MythTV supports this OpenChrome acceleration, but
it is not actually XvMC. It has enough in common with XvMC
that we call it "xvmc-via" internally.

I have read that Intel is working on some new acceleration
architecture which will work with the MPEG-4 codecs and
possibly some of Microsoft's video codecs. The XvMC
standard has defines for MPEG-4 and H.263, but no vendor
supports this and unless Intel decides to use XvMC for
their acceleration API it is unlikely that anyone will.
XvMC is an extension of XVideo which has a problematic
interface; it is very Microsoft Windowsy, which means 
the design allows one program crash can prevent you from
using your hardware until the video driver is reloaded.
So hopefully any future video API for Linux and other
Unixes will abandon XVideo to correct the problems.

-- Daniel



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