[mythtv] MythTV won't run with VIA CX700M2 chipset

David Shay david at shay.net
Fri Feb 1 04:41:49 UTC 2008

On Jan 23, 2008 8:51 AM, Daniel Kristjansson <danielk at cuymedia.net> wrote:

> On Wed, 2008-01-23 at 12:13 +0000, Oliver Maunder wrote:
> > I'm using the official VIA drivers because the Openchrome doesn't yet
> > I've tracked this down to DRM VSync calls. Commenting out the line
> > TESTVIDEOSYNC(DRMVideoSync) in VideoSync::BestMethod (in
> > libs/libmythtv/vsync.cpp) cures the problem.
> >
> > This leads to a second issue where video works but the colours are
> > messed up because MythTV is using I420 encoding which the driver
> > doesn't seem to like. This can be fixed by uncommenting the line
> >   in videoout_xv.cpp in 0.2.20. This #define isn't the SVN version,
> > but a similar one-line fix will work.
> The SVN version defaults to using the reversed I420 encoding that
> the AIT hack enabled. Unfortunately it seems many video card driver
> writers don't test I420 before shipping the drivers.
> > submit a patch, but I don't know what the policy is about hacking
> > around driver issues. The code would need to test for the VIA driver
> > and use the workarounds if it's founds. Is this sort of thing done
> > elsewhere in the code?
> Hacking around driver issues is something we do but don't like doing.
> When we do it we vastly prefer using a method that tests for the broken
> driver at run time and only applies the patch if needed.
> The GrabSuitibleXvPort() function in libs/libmythtv/videoout_xv.cpp
> queries the adaptor name, something like that could be used to test
> for the presence of the VIA drivers.
> -- Daniel
I've managed to catch up to the same point as Oliver -- installed on Ubuntu
and MythTV 0.20.2 and made patches as indicated in first e-mail.  Although
this does allow the board to work, it does not get MPEG-2 hardware
acceleration.  I get the following errors now:

2008-01-31 23:32:51.236 VideoOutputXv: XvMCTex: Init failed
2008-01-31 23:32:51.238 VideoOutputXv: XVideo Adaptor Name: 'XV_SWOV'
2008-01-31 23:32:54.872 TV: Changing from None to WatchingLiveTV
2008-01-31 23:32:54.932 Using realtime priority.
2008-01-31 23:32:55.165 Video timing method: RTC
2008-01-31 23:32:55.550 VideoOutputXv Error: XvMC output requested, but is
not supported by display.
Xlib:  extension "XVideo-MotionCompensation" missing on display ":0.0".

I already configured /etc/XvMCConfig to point to /usr/lib/libviaXvMCPro.so ,
so that's not the issue.  Also, I know the machine is capable since Via's
version of mplayer (VeMP) is working fine with HDTV sources on this machine
at relatively low CPU (~30%).  Any ideas where to go from here? Other
debugging steps to take?  Any reason to believe SVN would be better?
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