Knoppmyth, MythTV, XvMC and hairloss.

The following post is useless to most of the world. But, if you are tying to build a MythTv from the Knoppmyth Linux distribution, the following would have been nice to find if you are trying to get XvMC working with an Nvidia graphics card and using the Nvidia binary drivers (Knopmyth takes care of the instalation of those drivers for you.)

Add the following lines to /etc/X11/XF86Config-4 after 'Driver "Nvidia"' (this would also be true, I believe, in /etc/X11/xorg.conf if xorg is your desktop underbelly.) Pico is my text editor of choice, so I would "pico /etc/X11/XF86Config-4" as root at a command prompt.

Option "NvAGP" "1"
Option "RenderAccel" "1"

From my purely layman understanding of the Nvidia binary drivers for Linux, the "NvAGP" piece opens up the the card so you can use the acceleration (What about PCI or PCI Express as aposed to AGP Nvidia cards? Don't know. Don't own one.) and "RenderAccel" turns it on.

You will then need to CRTL-ALT-Backspace to restart gdm.

Then in MythTv manuver through the menus "Utilities/Setup" -> "Setup" -> "TV Settings" -> "Playback." Then select "Standard XVMC" for Preferred MPEG2 Playback. If you need to deinterlace the picture, choose the "Deinterlace" checkbox and select "BOB (2x framerate)" - it too uses XVMC for calculations.

Knoppmyth does a great job and really nails it on so many levels, including pre-compiling Linux with XvMC ready to go, but I needed to add those two lines to the configuration file.

And after 4 weeks of various hairloss, this was the voodoo that did the trick in being able to watch HDTV pulled in by a pcHDTV card and watching it on an old 1.7 Ghz Pentium 4.

If you ran into this because you are making the google rounds trying to get your MythTv box going, or you know a better way, please, leave a comment and let me know.