projects / deliverable / linux.git / blame
| 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> |