1 ================= 1 =================
2 ALSA BT87x Driver 2 ALSA BT87x Driver
3 ================= 3 =================
4 4
5 Intro 5 Intro
6 ===== 6 =====
7 7
8 You might have noticed that the bt878 grabber 8 You might have noticed that the bt878 grabber cards have actually
9 *two* PCI functions: 9 *two* PCI functions:
10 :: 10 ::
11 11
12 $ lspci 12 $ lspci
13 [ ... ] 13 [ ... ]
14 00:0a.0 Multimedia video controller: Brooktr 14 00:0a.0 Multimedia video controller: Brooktree Corporation Bt878 (rev 02)
15 00:0a.1 Multimedia controller: Brooktree Cor 15 00:0a.1 Multimedia controller: Brooktree Corporation Bt878 (rev 02)
16 [ ... ] 16 [ ... ]
17 17
18 The first does video, it is backward compatibl 18 The first does video, it is backward compatible to the bt848. The second
19 does audio. snd-bt87x is a driver for the sec 19 does audio. snd-bt87x is a driver for the second function. It's a sound
20 driver which can be used for recording sound ( 20 driver which can be used for recording sound (and *only* recording, no
21 playback). As most TV cards come with a short 21 playback). As most TV cards come with a short cable which can be plugged
22 into your sound card's line-in you probably do 22 into your sound card's line-in you probably don't need this driver if all
23 you want to do is just watching TV... 23 you want to do is just watching TV...
24 24
25 Some cards do not bother to connect anything t 25 Some cards do not bother to connect anything to the audio input pins of
26 the chip, and some other cards use the audio f 26 the chip, and some other cards use the audio function to transport MPEG
27 video data, so it's quite possible that audio 27 video data, so it's quite possible that audio recording may not work
28 with your card. 28 with your card.
29 29
30 30
31 Driver Status 31 Driver Status
32 ============= 32 =============
33 33
34 The driver is now stable. However, it doesn't 34 The driver is now stable. However, it doesn't know about many TV cards,
35 and it refuses to load for cards it doesn't kn 35 and it refuses to load for cards it doesn't know.
36 36
37 If the driver complains ("Unknown TV card foun 37 If the driver complains ("Unknown TV card found, the audio driver will
38 not load"), you can specify the ``load_all=1`` 38 not load"), you can specify the ``load_all=1`` option to force the driver to
39 try to use the audio capture function of your 39 try to use the audio capture function of your card. If the frequency of
40 recorded data is not right, try to specify the 40 recorded data is not right, try to specify the ``digital_rate`` option with
41 other values than the default 32000 (often it' 41 other values than the default 32000 (often it's 44100 or 64000).
42 42
43 If you have an unknown card, please mail the I 43 If you have an unknown card, please mail the ID and board name to
44 <alsa-devel@alsa-project.org>, regardless of wh 44 <alsa-devel@alsa-project.org>, regardless of whether audio capture works
45 or not, so that future versions of this driver 45 or not, so that future versions of this driver know about your card.
46 46
47 47
48 Audio modes 48 Audio modes
49 =========== 49 ===========
50 50
51 The chip knows two different modes (digital/an 51 The chip knows two different modes (digital/analog). snd-bt87x
52 registers two PCM devices, one for each mode. 52 registers two PCM devices, one for each mode. They cannot be used at
53 the same time. 53 the same time.
54 54
55 55
56 Digital audio mode 56 Digital audio mode
57 ================== 57 ==================
58 58
59 The first device (hw:X,0) gives you 16 bit ste 59 The first device (hw:X,0) gives you 16 bit stereo sound. The sample
60 rate depends on the external source which feed 60 rate depends on the external source which feeds the Bt87x with digital
61 sound via I2S interface. 61 sound via I2S interface.
62 62
63 63
64 Analog audio mode (A/D) 64 Analog audio mode (A/D)
65 ======================= 65 =======================
66 66
67 The second device (hw:X,1) gives you 8 or 16 b 67 The second device (hw:X,1) gives you 8 or 16 bit mono sound. Supported
68 sample rates are between 119466 and 448000 Hz 68 sample rates are between 119466 and 448000 Hz (yes, these numbers are
69 that high). If you've set the CONFIG_SND_BT87 69 that high). If you've set the CONFIG_SND_BT87X_OVERCLOCK option, the
70 maximum sample rate is 1792000 Hz, but audio d 70 maximum sample rate is 1792000 Hz, but audio data becomes unusable
71 beyond 896000 Hz on my card. 71 beyond 896000 Hz on my card.
72 72
73 The chip has three analog inputs. Consequentl 73 The chip has three analog inputs. Consequently you'll get a mixer
74 device to control these. 74 device to control these.
75 75
76 76
77 Have fun, 77 Have fun,
78 78
79 Clemens 79 Clemens
80 80
81 81
82 Written by Clemens Ladisch <clemens@ladisch.de> 82 Written by Clemens Ladisch <clemens@ladisch.de>
83 big parts copied from btaudio.txt by Gerd Knor< 83 big parts copied from btaudio.txt by Gerd Knorr <kraxel@bytesex.org>
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