1 2bttv and sound mini howto 3========================= 4 5There are a lot of different bt848/849/878/879 based boards available. 6Making video work often is not a big deal, because this is handled 7completely by the bt8xx chip, which is common on all boards. But 8sound is handled in slightly different ways on each board. 9 10To handle the grabber boards correctly, there is a array tvcards[] in 11bttv-cards.c, which holds the information required for each board. 12Sound will work only, if the correct entry is used (for video it often 13makes no difference). The bttv driver prints a line to the kernel 14log, telling which card type is used. Like this one: 15 16 bttv0: model: BT848(Hauppauge old) [autodetected] 17 18You should verify this is correct. If it isn't, you have to pass the 19correct board type as insmod argument, "insmod bttv card=2" for 20example. The file CARDLIST has a list of valid arguments for card. 21If your card isn't listed there, you might check the source code for 22new entries which are not listed yet. If there isn't one for your 23card, you can check if one of the existing entries does work for you 24(just trial and error...). 25 26Some boards have an extra processor for sound to do stereo decoding 27and other nice features. The msp34xx chips are used by Hauppauge for 28example. If your board has one, you might have to load a helper 29module like msp3400.o to make sound work. If there isn't one for the 30chip used on your board: Bad luck. Start writing a new one. Well, 31you might want to check the video4linux mailing list archive first... 32 33Of course you need a correctly installed soundcard unless you have the 34speakers connected directly to the grabber board. Hint: check the 35mixer settings too. ALSA for example has everything muted by default. 36 37 38How sound works in detail 39========================= 40 41Still doesn't work? Looks like some driver hacking is required. 42Below is a do-it-yourself description for you. 43 44The bt8xx chips have 32 general purpose pins, and registers to control 45these pins. One register is the output enable register 46(BT848_GPIO_OUT_EN), it says which pins are actively driven by the 47bt848 chip. Another one is the data register (BT848_GPIO_DATA), where 48you can get/set the status if these pins. They can be used for input 49and output. 50 51Most grabber board vendors use these pins to control an external chip 52which does the sound routing. But every board is a little different. 53These pins are also used by some companies to drive remote control 54receiver chips. Some boards use the i2c bus instead of the gpio pins 55to connect the mux chip. 56 57As mentioned above, there is a array which holds the required 58informations for each known board. You basically have to create a new 59line for your board. The important fields are these two: 60 61struct tvcard 62{ 63 [ ... ] 64 u32 gpiomask; 65 u32 audiomux[6]; /* Tuner, Radio, external, internal, mute, stereo */ 66}; 67 68gpiomask specifies which pins are used to control the audio mux chip. 69The corresponding bits in the output enable register 70(BT848_GPIO_OUT_EN) will be set as these pins must be driven by the 71bt848 chip. 72 73The audiomux[] array holds the data values for the different inputs 74(i.e. which pins must be high/low for tuner/mute/...). This will be 75written to the data register (BT848_GPIO_DATA) to switch the audio 76mux. 77 78 79What you have to do is figure out the correct values for gpiomask and 80the audiomux array. If you have Windows and the drivers four your 81card installed, you might to check out if you can read these registers 82values used by the windows driver. A tool to do this is available 83from ftp://telepresence.dmem.strath.ac.uk/pub/bt848/winutil, but it 84does'nt work with bt878 boards according to some reports I received. 85Another one with bt878 support is available from 86http://btwincap.sourceforge.net/Files/btspy2.00.zip 87 88You might also dig around in the *.ini files of the Windows applications. 89You can have a look at the board to see which of the gpio pins are 90connected at all and then start trial-and-error ... 91 92 93Starting with release 0.7.41 bttv has a number of insmod options to 94make the gpio debugging easier: 95 96bttv_gpio=0/1 enable/disable gpio debug messages 97gpiomask=n set the gpiomask value 98audiomux=i,j,... set the values of the audiomux array 99audioall=a set the values of the audiomux array (one 100 value for all array elements, useful to check 101 out which effect the particular value has). 102 103The messages printed with bttv_gpio=1 look like this: 104 105 bttv0: gpio: en=00000027, out=00000024 in=00ffffd8 [audio: off] 106 107en = output _en_able register (BT848_GPIO_OUT_EN) 108out = _out_put bits of the data register (BT848_GPIO_DATA), 109 i.e. BT848_GPIO_DATA & BT848_GPIO_OUT_EN 110in = _in_put bits of the data register, 111 i.e. BT848_GPIO_DATA & ~BT848_GPIO_OUT_EN 112 113 114 115Other elements of the tvcards array 116=================================== 117 118If you are trying to make a new card work you might find it useful to 119know what the other elements in the tvcards array are good for: 120 121video_inputs - # of video inputs the card has 122audio_inputs - historical cruft, not used any more. 123tuner - which input is the tuner 124svhs - which input is svhs (all others are labeled composite) 125muxsel - video mux, input->registervalue mapping 126pll - same as pll= insmod option 127tuner_type - same as tuner= insmod option 128*_modulename - hint whenever some card needs this or that audio 129 module loaded to work properly. 130has_radio - whenever this TV card has a radio tuner. 131no_msp34xx - "1" disables loading of msp3400.o module 132no_tda9875 - "1" disables loading of tda9875.o module 133needs_tvaudio - set to "1" to load tvaudio.o module 134 135If some config item is specified both from the tvcards array and as 136insmod option, the insmod option takes precedence. 137 138 139 140Good luck, 141 142 Gerd 143 144 145PS: If you have a new working entry, mail it to me. 146 147-- 148Gerd Knorr <kraxel@bytesex.org> 149