[mythtv-users] mythtv playback fails with ota atsc 720p

Steven Adeff adeffs.mythtv at gmail.com
Tue Sep 26 12:36:36 UTC 2006

On 9/25/06, Scott <list-mythtv at bluecamel.eml.cc> wrote:
> On Sep 23, 2006, at 5:18 PM, Scott wrote:
> > For one of the local OTA ATSC stations here (Raleigh / Durham NC
> > area, the station is WTVD 11.1) I'm seeing audio cut in and out 100%
> > of the time. If I run mythfrontend -v audio the output shows buffer
> > under runs, and lots of them. But wait! This same exact stream plays
> > perfectly fine with both xine and mplayer. By this I mean I can
> > either run mplayer dvb:// and tune the stream directly OR I can use
> > mplayer and xine to playback a stream that was recorded by MythTV.
> > The playback sounds fine with mplayer and xine.
> I'm starting to think this is a MythTV issue but I'm not sure in what
> way, yet. I made two test captures of the same channel and show then
> tried to play them back within MythTV. In MythTV I tuned to WTVD and
> watched live tv for about 20 seconds. I then exited out and saved the
> live tv mpeg file from the video directory. I named this file
> wtvd_mythtv.mpg In mplayer, tuned to the same WTVD channel and show
> as above and I ran "mplayer -dumpstream dvb://" for about 20 seconds
> then exited out. I renamed the captured file to wtvd_mplayer.mpg.
> I put both the wtvd_mplayer.mpg and wtvd_mythtv.mpg files into my
> MythTV Videos directory. Using the Internal player, the
> wtvd_mythtv.mpg file plays back badly. Audio is cutting in and out
> but video is smooth. Using the Internal player the wtvd_mplayer.mpg
> file plays back perfectly. This leads me to think that MythTV is
> doing something odd to the video stream before writing it to disk.
> Can anyone tell me what MythTV might be doing? Note also that running
> mplayer -v <file> on each sample seems to produce errors for the
> sample recorded by mythtv but not the one captured from mplayer.
> Both sample clips are available for download at http://donpoo.net/
> mythtv/. It would be great if other MythTV 0.20 users could drop
> these into their video directory and tell me if one or both clips
> play back okay. The problem to listen for is the sound track cutting
> in and out. The sound track should be an AC3 DD 5.1 channel format.

are you using XvMC? Is OpenGL Vsync enabled or disabled? do you have
audio buffering on?

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