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diff --git a/Documentation/media/v4l-drivers/bttv.rst b/Documentation/media/v4l-drivers/bttv.rst index f956ee264099..9b15a0cba283 100644 --- a/Documentation/media/v4l-drivers/bttv.rst +++ b/Documentation/media/v4l-drivers/bttv.rst @@ -438,126 +438,6 @@ parking, thus lowering arbitration performance. The Bt879 drivers must query for these non-compliant devices, and set the EN_VSFX bit only if required. -bttv and sound mini howto -------------------------- - -There are a lot of different bt848/849/878/879 based boards available. -Making video work often is not a big deal, because this is handled -completely by the bt8xx chip, which is common on all boards. But -sound is handled in slightly different ways on each board. - -To handle the grabber boards correctly, there is a array tvcards[] in -bttv-cards.c, which holds the information required for each board. -Sound will work only, if the correct entry is used (for video it often -makes no difference). The bttv driver prints a line to the kernel -log, telling which card type is used. Like this one: - -.. code-block:: none - - bttv0: model: BT848(Hauppauge old) [autodetected] - -You should verify this is correct. If it isn't, you have to pass the -correct board type as insmod argument, "insmod bttv card=2" for -example. The file CARDLIST has a list of valid arguments for card. -If your card isn't listed there, you might check the source code for -new entries which are not listed yet. If there isn't one for your -card, you can check if one of the existing entries does work for you -(just trial and error...). - -Some boards have an extra processor for sound to do stereo decoding -and other nice features. The msp34xx chips are used by Hauppauge for -example. If your board has one, you might have to load a helper -module like msp3400.o to make sound work. If there isn't one for the -chip used on your board: Bad luck. Start writing a new one. Well, -you might want to check the video4linux mailing list archive first... - -Of course you need a correctly installed soundcard unless you have the -speakers connected directly to the grabber board. Hint: check the -mixer settings too. ALSA for example has everything muted by default. - - -How sound works in detail -~~~~~~~~~~~~~~~~~~~~~~~~~ - -Still doesn't work? Looks like some driver hacking is required. -Below is a do-it-yourself description for you. - -The bt8xx chips have 32 general purpose pins, and registers to control -these pins. One register is the output enable register -(BT848_GPIO_OUT_EN), it says which pins are actively driven by the -bt848 chip. Another one is the data register (BT848_GPIO_DATA), where -you can get/set the status if these pins. They can be used for input -and output. - -Most grabber board vendors use these pins to control an external chip -which does the sound routing. But every board is a little different. -These pins are also used by some companies to drive remote control -receiver chips. Some boards use the i2c bus instead of the gpio pins -to connect the mux chip. - -As mentioned above, there is a array which holds the required -information for each known board. You basically have to create a new -line for your board. The important fields are these two: - -.. code-block:: c - - struct tvcard - { - [ ... ] - u32 gpiomask; - u32 audiomux[6]; /* Tuner, Radio, external, internal, mute, stereo */ - }; - -gpiomask specifies which pins are used to control the audio mux chip. -The corresponding bits in the output enable register -(BT848_GPIO_OUT_EN) will be set as these pins must be driven by the -bt848 chip. - -The audiomux\[\] array holds the data values for the different inputs -(i.e. which pins must be high/low for tuner/mute/...). This will be -written to the data register (BT848_GPIO_DATA) to switch the audio -mux. - - -What you have to do is figure out the correct values for gpiomask and -the audiomux array. If you have Windows and the drivers four your -card installed, you might to check out if you can read these registers -values used by the windows driver. A tool to do this is available -from ftp://telepresence.dmem.strath.ac.uk/pub/bt848/winutil, but it -doesn't work with bt878 boards according to some reports I received. -Another one with bt878 support is available from -http://btwincap.sourceforge.net/Files/btspy2.00.zip - -You might also dig around in the \*.ini files of the Windows applications. -You can have a look at the board to see which of the gpio pins are -connected at all and then start trial-and-error ... - - -Starting with release 0.7.41 bttv has a number of insmod options to -make the gpio debugging easier: - -.. code-block:: none - - bttv_gpio=0/1 enable/disable gpio debug messages - gpiomask=n set the gpiomask value - audiomux=i,j,... set the values of the audiomux array - audioall=a set the values of the audiomux array (one - value for all array elements, useful to check - out which effect the particular value has). - -The messages printed with bttv_gpio=1 look like this: - -.. code-block:: none - - bttv0: gpio: en=00000027, out=00000024 in=00ffffd8 [audio: off] - - en = output _en_able register (BT848_GPIO_OUT_EN) - out = _out_put bits of the data register (BT848_GPIO_DATA), - i.e. BT848_GPIO_DATA & BT848_GPIO_OUT_EN - in = _in_put bits of the data register, - i.e. BT848_GPIO_DATA & ~BT848_GPIO_OUT_EN - - Other elements of the tvcards array ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |