162306a36Sopenharmony_ci================= 262306a36Sopenharmony_ciALSA BT87x Driver 362306a36Sopenharmony_ci================= 462306a36Sopenharmony_ci 562306a36Sopenharmony_ciIntro 662306a36Sopenharmony_ci===== 762306a36Sopenharmony_ci 862306a36Sopenharmony_ciYou might have noticed that the bt878 grabber cards have actually 962306a36Sopenharmony_ci*two* PCI functions: 1062306a36Sopenharmony_ci:: 1162306a36Sopenharmony_ci 1262306a36Sopenharmony_ci $ lspci 1362306a36Sopenharmony_ci [ ... ] 1462306a36Sopenharmony_ci 00:0a.0 Multimedia video controller: Brooktree Corporation Bt878 (rev 02) 1562306a36Sopenharmony_ci 00:0a.1 Multimedia controller: Brooktree Corporation Bt878 (rev 02) 1662306a36Sopenharmony_ci [ ... ] 1762306a36Sopenharmony_ci 1862306a36Sopenharmony_ciThe first does video, it is backward compatible to the bt848. The second 1962306a36Sopenharmony_cidoes audio. snd-bt87x is a driver for the second function. It's a sound 2062306a36Sopenharmony_cidriver which can be used for recording sound (and *only* recording, no 2162306a36Sopenharmony_ciplayback). As most TV cards come with a short cable which can be plugged 2262306a36Sopenharmony_ciinto your sound card's line-in you probably don't need this driver if all 2362306a36Sopenharmony_ciyou want to do is just watching TV... 2462306a36Sopenharmony_ci 2562306a36Sopenharmony_ciSome cards do not bother to connect anything to the audio input pins of 2662306a36Sopenharmony_cithe chip, and some other cards use the audio function to transport MPEG 2762306a36Sopenharmony_civideo data, so it's quite possible that audio recording may not work 2862306a36Sopenharmony_ciwith your card. 2962306a36Sopenharmony_ci 3062306a36Sopenharmony_ci 3162306a36Sopenharmony_ciDriver Status 3262306a36Sopenharmony_ci============= 3362306a36Sopenharmony_ci 3462306a36Sopenharmony_ciThe driver is now stable. However, it doesn't know about many TV cards, 3562306a36Sopenharmony_ciand it refuses to load for cards it doesn't know. 3662306a36Sopenharmony_ci 3762306a36Sopenharmony_ciIf the driver complains ("Unknown TV card found, the audio driver will 3862306a36Sopenharmony_cinot load"), you can specify the ``load_all=1`` option to force the driver to 3962306a36Sopenharmony_citry to use the audio capture function of your card. If the frequency of 4062306a36Sopenharmony_cirecorded data is not right, try to specify the ``digital_rate`` option with 4162306a36Sopenharmony_ciother values than the default 32000 (often it's 44100 or 64000). 4262306a36Sopenharmony_ci 4362306a36Sopenharmony_ciIf you have an unknown card, please mail the ID and board name to 4462306a36Sopenharmony_ci<alsa-devel@alsa-project.org>, regardless of whether audio capture works 4562306a36Sopenharmony_cior not, so that future versions of this driver know about your card. 4662306a36Sopenharmony_ci 4762306a36Sopenharmony_ci 4862306a36Sopenharmony_ciAudio modes 4962306a36Sopenharmony_ci=========== 5062306a36Sopenharmony_ci 5162306a36Sopenharmony_ciThe chip knows two different modes (digital/analog). snd-bt87x 5262306a36Sopenharmony_ciregisters two PCM devices, one for each mode. They cannot be used at 5362306a36Sopenharmony_cithe same time. 5462306a36Sopenharmony_ci 5562306a36Sopenharmony_ci 5662306a36Sopenharmony_ciDigital audio mode 5762306a36Sopenharmony_ci================== 5862306a36Sopenharmony_ci 5962306a36Sopenharmony_ciThe first device (hw:X,0) gives you 16 bit stereo sound. The sample 6062306a36Sopenharmony_cirate depends on the external source which feeds the Bt87x with digital 6162306a36Sopenharmony_cisound via I2S interface. 6262306a36Sopenharmony_ci 6362306a36Sopenharmony_ci 6462306a36Sopenharmony_ciAnalog audio mode (A/D) 6562306a36Sopenharmony_ci======================= 6662306a36Sopenharmony_ci 6762306a36Sopenharmony_ciThe second device (hw:X,1) gives you 8 or 16 bit mono sound. Supported 6862306a36Sopenharmony_cisample rates are between 119466 and 448000 Hz (yes, these numbers are 6962306a36Sopenharmony_cithat high). If you've set the CONFIG_SND_BT87X_OVERCLOCK option, the 7062306a36Sopenharmony_cimaximum sample rate is 1792000 Hz, but audio data becomes unusable 7162306a36Sopenharmony_cibeyond 896000 Hz on my card. 7262306a36Sopenharmony_ci 7362306a36Sopenharmony_ciThe chip has three analog inputs. Consequently you'll get a mixer 7462306a36Sopenharmony_cidevice to control these. 7562306a36Sopenharmony_ci 7662306a36Sopenharmony_ci 7762306a36Sopenharmony_ciHave fun, 7862306a36Sopenharmony_ci 7962306a36Sopenharmony_ci Clemens 8062306a36Sopenharmony_ci 8162306a36Sopenharmony_ci 8262306a36Sopenharmony_ciWritten by Clemens Ladisch <clemens@ladisch.de> 8362306a36Sopenharmony_cibig parts copied from btaudio.txt by Gerd Knorr <kraxel@bytesex.org> 84