diff options
author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 18:20:36 -0400 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 18:20:36 -0400 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/sound/alsa/Bt87x.txt |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'Documentation/sound/alsa/Bt87x.txt')
-rw-r--r-- | Documentation/sound/alsa/Bt87x.txt | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/Documentation/sound/alsa/Bt87x.txt b/Documentation/sound/alsa/Bt87x.txt new file mode 100644 index 000000000000..11edb2fd2a5a --- /dev/null +++ b/Documentation/sound/alsa/Bt87x.txt | |||
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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 | <alsa-devel@lists.sf.net>, regardless of whether audio capture works or | ||
40 | 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 <clemens@ladisch.de> | ||
78 | big parts copied from btaudio.txt by Gerd Knorr <kraxel@bytesex.org> | ||