[mythtv] live TV stuttering

Hamish Moffatt hamish at cloud.net.au
Tue Apr 6 10:15:52 EDT 2004


I'm having a problem with live TV where Myth will start "stuttering".
It'll start within a second or two of changing to a channel, else it
will be ok. The audio and picture will pause then resume, over and over.

I can always fix it by quitting back to the menu and going straight back
to live TV (which goes to the same channel). I can usually fix it by
switching to another channel and back again.

When the stuttering occurs, there are no messages output to either the
mythfrontend terminal or the backend log (I have -v all).


One channel seems to cause it the most here. (Nine, for Australian
readers.) I'm running DVB-T. I get varying bit rate reports in the log
for this station;

Audiostream: Layer: 1  BRate: 320 kb/s  Freq: 0.0 kHz
Videostream: ASPECT: 16:9  Size = 720x576  FRate: 25 fps  BRate: 10.00 Mbit/s

Videostream: ASPECT: 16:9  Size = 720x576  FRate: 25 fps  BRate: 10.00 Mbit/s
Audiostream: Layer: 1  BRate: 256 kb/s  Freq: 44.1 kHz

Audiostream: Layer: 1  BRate: 128 kb/s  Freq: 48.0 kHz
Videostream: ASPECT: 16:9  Size = 720x576  FRate: 25 fps  BRate: 10.00 Mbit/s

Audiostream: Layer: 1  BRate: 352 kb/s  Freq: 32.0 kHz
Videostream: ASPECT: 16:9  Size = 720x576  FRate: 25 fps  BRate: 10.00 Mbit/s

I have other stations using higher bit rates (eg 15 Mbit/sec video).
There are other stations using both layer 1 and layer 2 audio. And
others using both the same picture size and a slightly different one. So
I can't find a pattern there.

I've tried tweaking my PCI bus latency settings while it's occurring but
it didn't help (using powertweak). I have an Athlon XP 2600+, plenty of 
RAM, fast disk etc.

I'm using linux 2.6.4 with OSS. I've seen it occur with 2.4.24.
I think it occurs much more often with ALSA. Pausing the live TV for a
few seconds then resuming does not help.

One time when it started occurring I switched to another channel, and it
didn't go away. Then the frontend starting print messages about audio
buffer overruns and prebuffering pauses. I haven't had that happen a
second time though.

I would welcome suggestions on how to debug this.... It's been present
for a few months here now. I've just checked it with absolute latest CVS.

thanks,
Hamish
-- 
Hamish Moffatt VK3SB <hamish at debian.org> <hamish at cloud.net.au>


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