HOWTO_Setup_Bt848_Audio_Capture_with_Alsa

Intro

Bt84x Audio Capture is present on quite a few bt84x TV Tuner cards. First, ensure that you have Bt87x Audio Capture support:

 localhost ~ # lspci | grep Bt8 | grep Audio
 00:09.1 Multimedia controller: Brooktree Corporation Bt878 Audio Capture (rev 11)
 localhost ~ #

Kernel Config

See ALSA/Install for information on configuring ALSA.

Here's the relevant configuration:

Userspace Config

Add the following entries to autoload the necessary modules:

  snd-bt87x index=1 load_all=1 enable=1
  bttv

When snd-bt87x is loaded, it will setup the Bt87x Audio as /dev/sound/dsp1 (ALSA: plughw:1,0) with the mixer at /dev/mixer1.

Getting Sound

On my Bt848 card, there's a 4-pin (RGGL) connector which can be connected to the AUX or CD input on the sound card (or motherboard - if integrated.) Thus, sound will come in via the respective channel.

If you don't have the connector, you can use a mono patch cable (Radio Shack Catalog #: 55020949) to take the sound from the Audio Out connector on the Bt848 card and connect it to your sound card's Line In.

Now, simply set your mixer levels, open up your favorite tuner app, set it to use the proper audio channel, and you should have sound.

If you only hear static, try the following:

 localhost ~ # rmmod bttv; sleep 5; modprobe bttv

Note: With some cards, you may experience static after a reboot.