[mythtv-users] "aplay /dev/dsp" gives "Unsigned 8 bit" output?

Gregor Hoffleit gregor at hoffleit.de
Wed Nov 5 16:17:51 EST 2003


I'm running into frequent system hangs with MythTV, and I'm trying to
find a way to track the cause down one by one.

Audio appearently is a frequent cause of system hangs with MythTV. My TV
card (some Pinnacle PCTV Studio Pro) doesn't support btaudio, therefore
I have looped the TV audio output inside the AUX port of my sound card
(some CMI-8738 based one). I'm using snd-cmipci of ALSA 0.9.6.

Now if I set the mixer as described (capture and mute AUX), and run
"aplay /dev/dsp", then all I get is 8 bit output, and obviously buffer
overruns:

    freefly:23> aplay /dev/dsp
    Playing raw data '/dev/dsp' : Unsigned 8 bit, Rate 8000 Hz, Mono
    xrun!!! (at least 13.151 ms long)
    xrun!!! (at least 15.359 ms long)
    xrun!!! (at least 15.490 ms long)
    xrun!!! (at least 15.474 ms long)
    xrun!!! (at least 15.486 ms long)

The output in fact really sounds like 8 bit and 8000 Hz, compared to the
TV output.

First question: Why is that only 8 bit? Is that a limitation of the
hardware (i.e. of the sound card), or is it some kind of configuration
problem?

Second question: Might that be the cause for hangs of the system?


I also encountered hangs with ffmpeg some time ago, so the problem also
might be the TV card (or something else. But how to debug these kind of
problems?).


I'm running Debian with the mythtv packages on this system, and the
problem is reproducable with various versions of MythTV and with various
kernels.

My mainboard is a K7S5A (Rev.4). I don't trust the on-board sound as
well, therefore I bought the CMI8738 card ;-). 


    Gregor


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