[mythtv] WinTV GO and btaudio... no sound

Bruce Markey mythtv-dev@snowman.net
Sun, 22 Dec 2002 02:12:28 -0800

Harondel J. Sibble wrote:
> On 21 Dec 2002 at 22:59, Bruce Markey wrote:
>>didn't like the on-board audio. When I added a second tuner,
>>I re-enabled the on-board as ALSA card-1 for the sole
>>purpose of using the DSP for the second tuner. This may
>>not apply to your system but I got around having to use
>>the btaudio module.
> How do you get all the audio _cleanly_ out to your speakers/stereo system 
> from both tv cards? 

Maybe I'm just fortunate but I'm not getting any of the hum
that others are experiencing. I've cranked up the volume
and don't really hear any production noise problems. If I
got btaudio to work ;-) I'd be concerned that it only samples
at 32000. I use 44100 for each card. In fact, if you haven't
tried 44100, give it a try to see if you get better results.

As far as speakers, this kind of confused me the first time
I tried. There are no speakers on the second (onboard) card.
"aplay /dev/dsp1" reads from the capture device (line-in)
on the second card (onboard) and writes to the PCM on the
first card (PCI slot) and out to the speakers. For alsamixer
on the second card, I only have line-in set to capture and
the volume up for Capture. Master, PCM, etc. are all 0 and

This is what I meant a couple weeks ago that the second
card didn't have speakers so you need aplay to hear the
audio for the second tuner. "aplay" reads the sampled
data from /dev/dsp1 the way MythTV will read the sampled
data from /dev/dsp1 . The btaudio doc suggests using sox
to read the DSP device whereas aplay is an ALSA specific
tool for doing the same thing.

> I want to get btaudio working so I won't have to go the 
> route you took.  Mind you I reenabled the onboard sound in the bios and setup 
> the appropriate modules for it so that I could if all else fails use both the 
> onboard and add in soundcards.  
> This just strikes me as inelegant and a mess cable and signal level wise 
> though.  

Here, I think, is where two sound card DSPs may be better
than a soundcard and btaudio. Both tuners are handled the
same way and should have the same roughly the same timbre.
They both go line-out to line-in to a DSP that is controlled
by an alsa driver. You use alsamixer to set the levels and
can easily check that they match (the "lots of shells" test
with two xawtv, two alsamixer and aplay to switch between
the two DSP devices).

> I have the creative desktop theatre 5.1 speaker system and I don't have 
> anymore inputs into the control module so, I am knocking on wood that we'll 
> get this sorted out soon.

Do you mean inputs to the speaker system? Again, as above,
you don't need any new wire from your onboard speaker-out
or line-out. You only use line-in (from tuner 2) so you
can use the DSP for /dev/dsp1.

Hope this helps,

--  bjm