[mythtv-users] Sound problem with BT878 capture card

[Lachek Butalek]

A question which, I'm sure, has been asked a million times before but
which I could not find a solution to after hours of Googling. Please
be gentle.

I have an analog BT878 capture card, a V-Stream VS-TV878RF more
commonly known as the KWorld BT878 tuner. It is card=78 in the BTTV
driver, and I'm also using tuner=2 which seems to work fine.

The card has an analog audio passthru port, into which I have plugged
a stereo 1/8" audio patch cable that ends in my sound card (Ensoniq
AudioPCI) Line port. Using this setup with xawtv - and the Line port
*not* muted - works fine: I can hear the channel I'm currently tuned
to in real time. Generally, audio playback (using mpg321, KDE system
sounds etc) separate from MythTV works fine on my system as well.

The issue is with recorded content, including "Live" TV - there is an
audio stream in the files (my video analyzers all report there is a
128kbit MP3 stream present) but it is dead silent. While in MythTV,
disabling mute on the Line port allows me to hear the channel (albeit
delayed, because of the encoding overhead of Live TV) being tuned to,
but the moment I enable mute as I'm supposed to I can no longer hear
the audio.

I've tried to mute the Line port, tune to a channel using xawtv and
then 'aplay /dev/dsp' but that results in nothing but a few clicks and
then nada - it reports a frequency of 8000bits (shouldn't that be
32000?) and mono (shouldn't that be stereo?), gives a few underrun
errors like it's supposed to, and then stops.

I've also tried to tinker with the settings in the Myth frontend, such
as setting the audio device to ALSA:default and the Device to default
- no apparent errors, but no sound either. Besides, since I have no
audio content in my recorded files I presume the problem is with the
backend rather than the frontend.

When configuring a capture device using mythtv-setup, there is an
option for audio device which is currently set to /dev/dsp. Is that
correct? Should it be changed to something - esp since I'm trying to
use all ALSA devices to narrow down the problem? Is there a more
low-level way - ie not so MythTV specific - to test recording audio
from an analog tuner?

Any assistance greatly appreciated.