[mythtv-users] PVR-250 audio occasionally drops out (to mono? ) - Pundit audio trouble?

[Buchanan, Paul]

I have been using OSS under RH9 on my Pundit without any audio problems.  Of
course, it could be that I just have never noticed the problem, but I kind
of doubt it.  My sound is coming from the TV speakers, so it would be less
noticeable than a full surround system.

Paul

-----Original Message-----
From: Will Dormann [mailto:wd at pobox.com]
Sent: Monday, September 15, 2003 2:00 PM
To: Discussion about mythtv
Subject: Re: [mythtv-users] PVR-250 audio occasionally drops out (to
mono?) - Pundit audio trouble?


OK, I've got some more information concerning this issue.

Occasionally when watching live TV or a recording, I'd get a glitch in my
audio where it seemed like it was dropping out to mono mode and then back
into stereo.   The glitch could last from about a second to maybe 5 seconds
in length.    During my initial analysis, I tried rewinding the video and
playing it back again, and the glitch was always in the same spot, so I
figured it was some sort of issue with my PVR-250 and/or MSP3400 chip.
The response I was getting seemed to point to a weak stereo signal.

Something strange that I noticed was that after a while I could almost
predict when these audio glitches would occur.  That is, there were certain
circumstances that would trigger the glitches.  Mostly during dialog.   If
I recorded a band playing, it would always seem to be fine.

Anyway, after some in-depth testing, I have discovered that the glitches do
*not* always occur in the same spots when rewinding and playing back again.
  I recorded a show that was particularly glitchy when I was watching it.
But I played it back on my Windows machine and there were no glitches at
all!   There seemed to be some parts that had a high chance of being
glitchy when played back on my MythTV box.     But when rewinding and
playing back over and over again, I discovered that the glitch was not
always in the exact same spot.  In fact, sometimes there were no glitches
at all.

Which leads me to believe that there's some sort of problem with the driver
for my Pundit's onboard audio.   I'm using the Gentoo ALSA drivers and also
alsa-oss.    (Is the latter required?  I've always just gotten both....)

Has anybody had any similar trouble with their Pundit's audio?    It's hard
to describe, but I'll be watching a recording and there will be a split
second of silence and the audio switches to mono (or maybe just right
channel... it's hard to tell) for a second or two, and then back to stereo.
  It can get a bit distracting.

There are quite a few Alsa mixer options.   Are there any particular
settings I need to make sure are set?   Since the probability of audio
glitching seems to be dependent on the input, it's almost as if the audio
could be "clipping", but I've never seen clipping cause the symptoms I'm
seeing.     Since I don't require full duplex or anything, would it be
worth trying the OSS driver for the Pundit's audio, rather than ALSA?
What do you other Pundit users use?


many thanks!
-WD