[pulseaudio-discuss] tv-card -> on-board -> sound-card

[Tanu Kaskinen]

2009/6/28 Andreas Herrmann <andreasherrmann at student.ethz.ch>:
> The software and the symptoms:
> I'm running Ubuntu Linux 8.04 (Hardy) with pulseaudio, of course ;).
> XawTV is my television application of choice.
> The Audigy is configured as default sink and works for music, system
> beeps and so on, but not for television.
> If I plug headphones to the on-board speaker-jack I can hear the
> television sound coming out of the headphones, while XawTV is running.
> How ever if I look at the
> PulseAudio_Manager->Devices->Properties->Volume_Meter window the only
> device that 'shows' some sound-output is the Audigy (music), but the
> on-board sink and every source listed pretends to be quiet, even if I
> can hear the TV sound with the headphones.

The on-board sound card driver is looping input directly to output, so
the audio doesn't pass through PA.

> Finally. My question:
> How do I make pulseaudio to pass the tv-sound to the Audigy, such that I
> can hear the television sound with the speakers connected to the
> sound-card?

You have to copy (record and play back) the on-board line-in to
Audigy. It would make most sense to do this completely inside PA, but
unfortunately it's not supported. A crappy (really) solution is to
record the input with parec and pipe the audio to pacat. The command
would look something like this:

$ parec -d <on-board source> | pacat -d <audigy sink>

Another solution might be to use RTP. That's a kludge too, but might
perform better if it compensates for the clock drift between the
on-board card and Audigy. If someone can confirm this, I'd be
interested. You put these two lines to default.pa:

load-module module-rtp-send source=<on-board source> loop=true
load-module module-rtp-recv sink=<audigy sink>

That sends the audio to the network too. If that's a problem, I would
guess (no personal experience) you can avoid that by giving a third
parameter to module-rtp-send: destination=127.0.0.1. Maybe you will
then need to give sap_address=127.0.0.1 to module-rtp-recv too? And if
the stream is targeted to localhost, maybe the loop parameter is
unnecessary?

-- 
Tanu Kaskinen