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

Scott list-mythtv at bluecamel.eml.cc
Mon Sep 25 16:06:17 UTC 2006

On Sep 23, 2006, at 5:18 PM, Scott wrote:

> Greets.
> 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.

Suggestions on where to go from here?


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