Based on kernel version 4.7.2. Page generated on 2016-08-22 22:48 EST.
1 2 bttv and sound mini howto 3 ========================= 4 5 There are a lot of different bt848/849/878/879 based boards available. 6 Making video work often is not a big deal, because this is handled 7 completely by the bt8xx chip, which is common on all boards. But 8 sound is handled in slightly different ways on each board. 9 10 To handle the grabber boards correctly, there is a array tvcards[] in 11 bttv-cards.c, which holds the information required for each board. 12 Sound will work only, if the correct entry is used (for video it often 13 makes no difference). The bttv driver prints a line to the kernel 14 log, telling which card type is used. Like this one: 15 16 bttv0: model: BT848(Hauppauge old) [autodetected] 17 18 You should verify this is correct. If it isn't, you have to pass the 19 correct board type as insmod argument, "insmod bttv card=2" for 20 example. The file CARDLIST has a list of valid arguments for card. 21 If your card isn't listed there, you might check the source code for 22 new entries which are not listed yet. If there isn't one for your 23 card, you can check if one of the existing entries does work for you 24 (just trial and error...). 25 26 Some boards have an extra processor for sound to do stereo decoding 27 and other nice features. The msp34xx chips are used by Hauppauge for 28 example. If your board has one, you might have to load a helper 29 module like msp3400.o to make sound work. If there isn't one for the 30 chip used on your board: Bad luck. Start writing a new one. Well, 31 you might want to check the video4linux mailing list archive first... 32 33 Of course you need a correctly installed soundcard unless you have the 34 speakers connected directly to the grabber board. Hint: check the 35 mixer settings too. ALSA for example has everything muted by default. 36 37 38 How sound works in detail 39 ========================= 40 41 Still doesn't work? Looks like some driver hacking is required. 42 Below is a do-it-yourself description for you. 43 44 The bt8xx chips have 32 general purpose pins, and registers to control 45 these pins. One register is the output enable register 46 (BT848_GPIO_OUT_EN), it says which pins are actively driven by the 47 bt848 chip. Another one is the data register (BT848_GPIO_DATA), where 48 you can get/set the status if these pins. They can be used for input 49 and output. 50 51 Most grabber board vendors use these pins to control an external chip 52 which does the sound routing. But every board is a little different. 53 These pins are also used by some companies to drive remote control 54 receiver chips. Some boards use the i2c bus instead of the gpio pins 55 to connect the mux chip. 56 57 As mentioned above, there is a array which holds the required 58 information for each known board. You basically have to create a new 59 line for your board. The important fields are these two: 60 61 struct tvcard 62 { 63 [ ... ] 64 u32 gpiomask; 65 u32 audiomux[6]; /* Tuner, Radio, external, internal, mute, stereo */ 66 }; 67 68 gpiomask specifies which pins are used to control the audio mux chip. 69 The corresponding bits in the output enable register 70 (BT848_GPIO_OUT_EN) will be set as these pins must be driven by the 71 bt848 chip. 72 73 The 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 75 written to the data register (BT848_GPIO_DATA) to switch the audio 76 mux. 77 78 79 What you have to do is figure out the correct values for gpiomask and 80 the audiomux array. If you have Windows and the drivers four your 81 card installed, you might to check out if you can read these registers 82 values used by the windows driver. A tool to do this is available 83 from ftp://telepresence.dmem.strath.ac.uk/pub/bt848/winutil, but it 84 does'nt work with bt878 boards according to some reports I received. 85 Another one with bt878 support is available from 86 http://btwincap.sourceforge.net/Files/btspy2.00.zip 87 88 You might also dig around in the *.ini files of the Windows applications. 89 You can have a look at the board to see which of the gpio pins are 90 connected at all and then start trial-and-error ... 91 92 93 Starting with release 0.7.41 bttv has a number of insmod options to 94 make the gpio debugging easier: 95 96 bttv_gpio=0/1 enable/disable gpio debug messages 97 gpiomask=n set the gpiomask value 98 audiomux=i,j,... set the values of the audiomux array 99 audioall=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). 102 103 The messages printed with bttv_gpio=1 look like this: 104 105 bttv0: gpio: en=00000027, out=00000024 in=00ffffd8 [audio: off] 106 107 en = output _en_able register (BT848_GPIO_OUT_EN) 108 out = _out_put bits of the data register (BT848_GPIO_DATA), 109 i.e. BT848_GPIO_DATA & BT848_GPIO_OUT_EN 110 in = _in_put bits of the data register, 111 i.e. BT848_GPIO_DATA & ~BT848_GPIO_OUT_EN 112 113 114 115 Other elements of the tvcards array 116 =================================== 117 118 If you are trying to make a new card work you might find it useful to 119 know what the other elements in the tvcards array are good for: 120 121 video_inputs - # of video inputs the card has 122 audio_inputs - historical cruft, not used any more. 123 tuner - which input is the tuner 124 svhs - which input is svhs (all others are labeled composite) 125 muxsel - video mux, input->registervalue mapping 126 pll - same as pll= insmod option 127 tuner_type - same as tuner= insmod option 128 *_modulename - hint whenever some card needs this or that audio 129 module loaded to work properly. 130 has_radio - whenever this TV card has a radio tuner. 131 no_msp34xx - "1" disables loading of msp3400.o module 132 no_tda9875 - "1" disables loading of tda9875.o module 133 needs_tvaudio - set to "1" to load tvaudio.o module 134 135 If some config item is specified both from the tvcards array and as 136 insmod option, the insmod option takes precedence. 137 138 139 140 Good luck, 141 142 Gerd 143 144 145 PS: If you have a new working entry, mail it to me. 146 147 -- 148 Gerd Knorr <kraxel@bytesex.org>