Based on kernel version 4.1. Page generated on 2015-06-28 12:14 EST.
1 Intro 2 ===== 3 4 You might have noticed that the bt878 grabber cards have actually 5 _two_ PCI functions: 6 7 $ lspci 8 [ ... ] 9 00:0a.0 Multimedia video controller: Brooktree Corporation Bt878 (rev 02) 10 00:0a.1 Multimedia controller: Brooktree Corporation Bt878 (rev 02) 11 [ ... ] 12 13 The first does video, it is backward compatible to the bt848. The second 14 does audio. snd-bt87x is a driver for the second function. It's a sound 15 driver which can be used for recording sound (and _only_ recording, no 16 playback). As most TV cards come with a short cable which can be plugged 17 into your sound card's line-in you probably don't need this driver if all 18 you want to do is just watching TV... 19 20 Some cards do not bother to connect anything to the audio input pins of 21 the chip, and some other cards use the audio function to transport MPEG 22 video data, so it's quite possible that audio recording may not work 23 with your card. 24 25 26 Driver Status 27 ============= 28 29 The driver is now stable. However, it doesn't know about many TV cards, 30 and it refuses to load for cards it doesn't know. 31 32 If the driver complains ("Unknown TV card found, the audio driver will 33 not load"), you can specify the load_all=1 option to force the driver to 34 try to use the audio capture function of your card. If the frequency of 35 recorded data is not right, try to specify the digital_rate option with 36 other values than the default 32000 (often it's 44100 or 64000). 37 38 If you have an unknown card, please mail the ID and board name to 39 <email@example.com>, regardless of whether audio capture works 40 or not, so that future versions of this driver know about your card. 41 42 43 Audio modes 44 =========== 45 46 The chip knows two different modes (digital/analog). snd-bt87x 47 registers two PCM devices, one for each mode. They cannot be used at 48 the same time. 49 50 51 Digital audio mode 52 ================== 53 54 The first device (hw:X,0) gives you 16 bit stereo sound. The sample 55 rate depends on the external source which feeds the Bt87x with digital 56 sound via I2S interface. 57 58 59 Analog audio mode (A/D) 60 ======================= 61 62 The second device (hw:X,1) gives you 8 or 16 bit mono sound. Supported 63 sample rates are between 119466 and 448000 Hz (yes, these numbers are 64 that high). If you've set the CONFIG_SND_BT87X_OVERCLOCK option, the 65 maximum sample rate is 1792000 Hz, but audio data becomes unusable 66 beyond 896000 Hz on my card. 67 68 The chip has three analog inputs. Consequently you'll get a mixer 69 device to control these. 70 71 72 Have fun, 73 74 Clemens 75 76 77 Written by Clemens Ladisch <firstname.lastname@example.org> 78 big parts copied from btaudio.txt by Gerd Knorr <email@example.com>