[mythtv-users] Yet another sound problem

[David Wadler]

> David Wadler wrote:
<snip>
> > I had to wipe my drive (don't ask) and am now running a 2.6.6 kernel.
> > The new kernel made it very easy to get ALSA up-and-running and I'm
> > using it in Xine, mplayer, XMMS, and other apps.  However, when I set
> > Myth to use ALSA:default, I got choppy video (lots of prebuffering
> > messages) and audio that wasn't quite right.  It sounds clipped.  I
> > played with the mixer levels, and no matter how low I go, there
> > remains distortion.  I switched to /dev/dsp and /dev/adsp, both of
> > which work, but both of which have the same audio distortion.  In
> > addition to adjusting the levels with my soundcard, I also tried to
> > adjust the TV-Card's mixer, by doing alsamixer -c 1.  I can only
> > adjust the level attached to "Capture" and changing it doesn't have
> > any effect.
<snip>

> > Loaded modules:
> >
> > Module                  Size  Used by
> > snd_pcm_oss            48932  2
> > snd_mixer_oss          17344  1 snd_pcm_oss
> > tvmixer                 4720  1
> > snd_bt87x              11204  0
> > tuner                  17356  0
> > tvaudio                20428  0
> > tda7432                 6924  0
> > bttv                  143980  2
> > video_buf              16516  1 bttv
> > i2c_algo_bit            8904  1 bttv
> > btcx_risc               3848  1 bttv
> > i2c_core               18756  6
> > tvmixer,tuner,tvaudio,tda7432,bttv,i2c_algo_bit
> > snd_via82xx            22208  2
> > snd_pcm                84580  3 snd_pcm_oss,snd_bt87x,snd_via82xx
> > snd_timer              20996  1 snd_pcm
> > snd_ac97_codec         61444  1 snd_via82xx
> > snd_page_alloc          8964  3 snd_bt87x,snd_via82xx,snd_pcm
> > snd_mpu401_uart         6144  1 snd_via82xx
> > snd_rawmidi            20128  1 snd_mpu401_uart
> > snd_seq_device          6536  1 snd_rawmidi
> > snd                    46564  10
> >
snd_pcm_oss,snd_mixer_oss,snd_bt87x,snd_via82xx,snd_pcm,snd_timer,snd_ac97_c
odec,snd_mpu401_uart,snd_rawmidi,snd_seq_device
> >
> > Thanks,
> > David
>
> What kind of audio hardware are you running and what kind of capture
> card?  Are you using a soundcard with the audio from your capture card
> going to the line-in on your soundcard?  Judging from the tvaudio being
> loaded I guess you are pulling the sound directly from your capture
> card.  I recently had a problem with btaudio and solved it (crossing
> fingers) by using the ALSA bt87x driver instead of btaudio.  Perhaps if
> you loaded that to pull sound from your card you might have better luck.
>
> BTW, the native ALSA support in Myth is not ready for primetime so for
> sure you should use OSS emulation on /dev/adsp.  I've tried to put
> together some patches to improve the ALSA support but they're a work in
> progress still and not in CVS yet.

Kevin, thanks for the response.  Let me go address the things you brought up
one-by-one:

1)  Audio hardware:  Multimedia audio controller: VIA Technologies, Inc.
VT8233/A/8235/8237 AC97 Audio Controller  (It's pretty generic, onboard
audio, but is more than adequate for my needs and has a fairly large
userbase.)

2)  Yes, I have the audio from my capture card going to the line-in on my
soundcard.

3)  I never explicitly load tvaudio; it seems to load when bttv does.  In
any case, it doesn't seem to do anything.  I get not-very-good sound
regardless of whether the module is loaded or not.

4)  I've been playing with the ALSA bt87x driver.  Loading it creates
/dev/dsp1.  However, MythTV reports "No such device" when I try to assign
sound to it.  I've just been running modprobe to load it; are there
configuration options I'm missing?  Right now, it doesn't seem to do
anything...apparently a recurring theme with my tv-related sound modules.

5)  I'm looking forward to ALSA -- it's been a pleasure to use with my other
apps.  I've been using /dev/adsp in Myth, but the sound isn't quite right.
Hence this email exchange. :-)

Thanks again,
David