[mythtv] XvMC VLD extension (beginnings of fix)

Terry Barnaby terry1 at beam.ltd.uk
Tue Sep 26 19:47:56 UTC 2006

Michael Weber wrote:
>>>>>> 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
>>> myth.
>>> mike
>>> _______________________________________________
>> Haven't had a chance yet, but can you tell me where and how to apply
>> this patch?  I'm not home yet, but will be later this evening and
>> would like to roll it in to see the progress and give feedback.
>> Thanks!
>> -Chad
> The latest SVN should work, and the patch should be applied in the
> mythtv/libs/libmythtv directory.  I should have run the patch from the
> SVN root, sorry for the confusion.
> mike
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The stuttering you are seeing sound like the same problem I am seeing 
and trying to track down.
See the thread "[mythtv] XvMC VLD Decoding stuttering problems on some 


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