Commit | Line | Data |
---|---|---|
1da177e4 LT |
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 | |
4505179c RH |
39 | <alsa-devel@alsa-project.org>, regardless of whether audio capture works |
40 | or not, so that future versions of this driver know about your card. | |
1da177e4 LT |
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 <clemens@ladisch.de> | |
78 | big parts copied from btaudio.txt by Gerd Knorr <kraxel@bytesex.org> |