[mythtv] XvMC VLD extension (beginnings of fix)

Michael Weber mtweber at gmail.com
Sun Sep 24 03:10:42 UTC 2006

> > > I tried the mythtv-vid branch for Via SP13000 HDTV decoding and all I
> > > get is a blank screen with good audio when trying to play 1080i
> > > content.

> Just an FYI:
> Same thing is happening to me.  Blank screen, smooth audio with the
> VID branch on 1080i content using very new SVN openchrome drivers on a
> CN400 (SP13000 as well as Commell 667-T).  720p stutters far too much
> to be watchable either, but I'm holding out, choosing which 'bugs' to
> file, 1 bug-per-project at a time preferably ;)

After some work trying to understand the code, I have a patch for
1080i playback on the CN400 (well at least for the SP13000).  I
haven't attached the patch to the trac yet because all this patch does
is get the video to display instead of the blue screen.  The display
is good, but now the decoder can't to keep.  I have spent some time
looking into this since xine can play 1080 pretty easily.

I think the the problem may be with the communication with the
openchrome driver.  In the driver, a mutex locks each call.  So while
myth is placing the image with PutSurface, the decoder cannot access
PutSlice because of the mutex.  Now, xine accomplishes it with the
locks somehow, but I haven't figured out how yet.

I already tried to move the SyncSurface from frame end to just before
the PutSurface.  This reduces the number of buffering pauses for 1080i
and eliminates them from 720p, but it creates other problems with
ffw/rew and skipping.

Another note about HD playback on CN400s, with 720p, even in xine
(which doesn't not have the stuttering problem like myth), the video
is shuffled (repeated blocks of lines on the left and right).  I have
not started looking into this yet, but it seems like there is a
problem with they way the slices get to the CN400 in both xine and

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