[plug] digital TV

[Craig Ringer]

> I have an old provideo pv951. The sound never worked properly on the
> early ones. We ended modifying a cdrom sound cable plugging one end into
> the on-board line1 and figuring out which pins were left and right on
> the video card. So when i record, i record line1! The side effect is
> when i turn off the tuner program eg gradio the card is still tuned in
> until it is completely powered off.

I'm pretty sure that's just the way the saa7134 chipset works. It 
doesn't have a proper DSP, instead it decodes the TV audio and dumps it 
in analog form to the line-out port on the card. Mine's external :-( so 
I have a short cable running from my tv card to my sound card's line in.

As for the radio not turning off when you exit the app - properly 
written apps will generally mute the card when they exit - most of the 
video ones do this, but the radio-only ones don't seem to know how. I 
kind of like it though - I can always "turn off" the radio by muting 
line-in, and there are some advantages. I've got my xfce4 panel set up 
with a menu of radio stations, and can tune to them easily from there. 
As the panel has tear-off menus, I can tear it off and float it 
somewhere if I want. Works a treat - each command just calls 'radio -f 
99.35' (for example). As I have line-in volume presets in the menu too, 
I never use `radio` or `gradio` interactively at all.

I suspect the reason I can't record sound with mencoder is because it's 
is stubbornly looking for an audio channel via the v4l device, and won't 
use the sound card's line in for an audio source. Apparently the bttv 
driver provides a v4l sound source.

The audio behaviour is also very useful when recording - apps don't have 
to know anything about v4l, only how to read from line in. Very nice 
with oggenc and cron :-)

Craig Ringer

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