|You might have noticed that the bt878 grabber cards have actually
|_two_ PCI functions:
|[ ... ]
|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 second
|does audio. snd-bt87x is a driver for the second function. It's a sound
|driver which can be used for recording sound (and _only_ recording, no
|playback). As most TV cards come with a short cable which can be plugged
|into your sound card's line-in you probably don't need this driver if all
|you want to do is just watching TV...
|Some cards do not bother to connect anything to the audio input pins of
|the chip, and some other cards use the audio function to transport MPEG
|video data, so it's quite possible that audio recording may not work
|with your card.
|The driver is now stable. However, it doesn't know about many TV cards,
|and it refuses to load for cards it doesn't know.
|If the driver complains ("Unknown TV card found, the audio driver will
|not load"), you can specify the load_all=1 option to force the driver to
|try to use the audio capture function of your card. If the frequency of
|recorded data is not right, try to specify the digital_rate option with
|other values than the default 32000 (often it's 44100 or 64000).
|If you have an unknown card, please mail the ID and board name to
|<email@example.com>, regardless of whether audio capture works
|or not, so that future versions of this driver know about your card.
|The chip knows two different modes (digital/analog). snd-bt87x
|registers two PCM devices, one for each mode. They cannot be used at
|the same time.
|Digital audio mode
|The first device (hw:X,0) gives you 16 bit stereo sound. The sample
|rate depends on the external source which feeds the Bt87x with digital
|sound via I2S interface.
|Analog audio mode (A/D)
|The second device (hw:X,1) gives you 8 or 16 bit mono sound. Supported
|sample rates are between 119466 and 448000 Hz (yes, these numbers are
|that high). If you've set the CONFIG_SND_BT87X_OVERCLOCK option, the
|maximum sample rate is 1792000 Hz, but audio data becomes unusable
|beyond 896000 Hz on my card.
|The chip has three analog inputs. Consequently you'll get a mixer
|device to control these.
|Written by Clemens Ladisch <firstname.lastname@example.org>
|big parts copied from btaudio.txt by Gerd Knorr <email@example.com>