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-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 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.
-Driver Status
-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
-<>, regardless of whether audio capture works
-or not, so that future versions of this driver know about your card.
-Audio modes
-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.
-Have fun,
- Clemens
-Written by Clemens Ladisch <>
-big parts copied from btaudio.txt by Gerd Knorr <>