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1=================2ALSA BT87x Driver3=================4 5Intro6=====7 8You might have noticed that the bt878 grabber cards have actually9*two* PCI functions:10::11 12 $ lspci13 [ ... ]14 00:0a.0 Multimedia video controller: Brooktree Corporation Bt878 (rev 02)15 00:0a.1 Multimedia controller: Brooktree Corporation Bt878 (rev 02)16 [ ... ]17 18The first does video, it is backward compatible to the bt848. The second19does audio. snd-bt87x is a driver for the second function. It's a sound20driver which can be used for recording sound (and *only* recording, no21playback). As most TV cards come with a short cable which can be plugged22into your sound card's line-in you probably don't need this driver if all23you want to do is just watching TV...24 25Some cards do not bother to connect anything to the audio input pins of26the chip, and some other cards use the audio function to transport MPEG27video data, so it's quite possible that audio recording may not work28with your card.29 30 31Driver Status32=============33 34The driver is now stable. However, it doesn't know about many TV cards,35and it refuses to load for cards it doesn't know.36 37If the driver complains ("Unknown TV card found, the audio driver will38not load"), you can specify the ``load_all=1`` option to force the driver to39try to use the audio capture function of your card. If the frequency of40recorded data is not right, try to specify the ``digital_rate`` option with41other values than the default 32000 (often it's 44100 or 64000).42 43If you have an unknown card, please mail the ID and board name to44<alsa-devel@alsa-project.org>, regardless of whether audio capture works45or not, so that future versions of this driver know about your card.46 47 48Audio modes49===========50 51The chip knows two different modes (digital/analog). snd-bt87x52registers two PCM devices, one for each mode. They cannot be used at53the same time.54 55 56Digital audio mode57==================58 59The first device (hw:X,0) gives you 16 bit stereo sound. The sample60rate depends on the external source which feeds the Bt87x with digital61sound via I2S interface.62 63 64Analog audio mode (A/D)65=======================66 67The second device (hw:X,1) gives you 8 or 16 bit mono sound. Supported68sample rates are between 119466 and 448000 Hz (yes, these numbers are69that high). If you've set the CONFIG_SND_BT87X_OVERCLOCK option, the70maximum sample rate is 1792000 Hz, but audio data becomes unusable71beyond 896000 Hz on my card.72 73The chip has three analog inputs. Consequently you'll get a mixer74device to control these.75 76 77Have fun,78 79 Clemens80 81 82Written by Clemens Ladisch <clemens@ladisch.de>83big parts copied from btaudio.txt by Gerd Knorr <kraxel@bytesex.org>84