Intro=====people start bugging me about this with questions, looks like Ishould write up some documentation for this beast.  That way Idon't have to answer that much mails I hope.  Yes, I'm lazy...You might have noticed that the bt878 grabber cards have actually_two_ PCI functions:$ lspci[ ... ]00:0a.0 Multimedia video controller: Brooktree Corporation Bt878 (rev 02)00:0a.1 Multimedia controller: Brooktree Corporation Bt878 (rev 02)[ ... ]The first does video, it is backward compatible to the bt848.  The seconddoes audio.  btaudio is a driver for the second function.  It's a sounddriver which can be used for recording sound (and _only_ recording, noplayback).  As most TV cards come with a short cable which can be pluggedinto your sound card's line-in you probably don't need this driver if allyou want to do is just watching TV...Driver Status=============Still somewhat experimental.  The driver should work stable, i.e. itshould'nt crash your box.  It might not work as expected, have bugs,not being fully OSS API compilant, ...Latest versions are available from http://bytesex.org/bttv/, thedriver is in the bttv tarball.  Kernel patches might be available too,have a look at http://bytesex.org/bttv/listing.html.The chip knows two different modes.  btaudio registers two dspdevices, one for each mode.  They can not be used at the same time.Digital audio mode==================The chip gives you 16 bit stereo sound.  The sample rate depends onthe external source which feeds the bt878 with digital sound via I2Sinterface.  There is a insmod option (rate) to tell the driver whichsample rate the hardware uses (32000 is the default).One possible source for digital sound is the msp34xx audio processorchip which provides digital sound via I2S with 32 kHz sample rate.  MyHauppauge board works this way.The Osprey-200 reportly gives you digital sound with 44100 Hz samplerate.  It is also possible that you get no sound at all.analog mode (A/D)=================You can tell the driver to use this mode with the insmod option "analog=1".The chip has three analog inputs.  Consequently you'll get a mixer deviceto control these.The analog mode supports mono only.  Both 8 + 16 bit.  Both are _signed_int, which is uncommon for the 8 bit case.  Sample rate range is 119 kHzto 448 kHz.  Yes, the number of digits is correct.  The driver supportsdownsampling by powers of two, so you can ask for more usual sample rateslike 44 kHz too.With my Hauppauge I get noisy sound on the second input (mapped to line2by the mixer device).  Others get a useable signal on line1.some examples=============* read audio data from btaudio (dsp2), send to es1730 (dsp,dsp1):  $ sox -w -r 32000 -t ossdsp /dev/dsp2 -t ossdsp /dev/dsp* read audio data from btaudio, send to esound daemon (which might be  running on another host):  $ sox -c 2 -w -r 32000 -t ossdsp /dev/dsp2 -t sw - | esdcat -r 32000  $ sox -c 1 -w -r 32000 -t ossdsp /dev/dsp2 -t sw - | esdcat -m -r 32000Have fun,  Gerd-- Gerd Knorr <kraxel@bytesex.org>