[mythtv-users] Watching LiveTV with a Matrox G200

Martin Ebourne lists at ebourne.me.uk
Sun Sep 24 23:17:43 UTC 2006


On Mon, 25 Sep 2006 23:18:38 +0200, digitom wrote:
> My MythTV works almost fine, until i have changed the video card. The
> Matrox G200 is better for TV-Out then the Radeon. (TV-Out over VGA-RGB to
> Scart with an resolution of 720x576 at 50Hz)
> ...
> In fact, the only thing that is not working, ist watching TV in
> Fullscreen-mode.
> When i switch to LiveTV (dvb-s) or want to watch a record i get only a
> blue-screen.
> The remote works, and sound is also ok. I can also see the preview-video
> at the recordings.

The problem as you suspected is XV. The matrox cards just do not support
the Backend Scaler (as used by XV) on interlaced output (including the
tvout).

You can set the environment variable NO_XV=1 before running mythfrontend
which will disable XV and will get you a picture. Unfortunately it will
use more processor (or at least more bus bandwidth which has a similar
effect), and crucially the double buffering provided by XV will be lost.
Hence you will get tearing of the picture.

The card provides vsync, and if someone implemented double buffering by
moving the video base address it could be made to work very well. DirectFB
gets close on the G400 and above but compiling MythTV for it is not very
rewarding in my experience.

Cheers,

Martin.



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