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-
-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:
-
- 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
-informations for each known board. You basically have to create a new
-line for your board. The important fields are these two:
-
-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
-does'nt work with bt878 boards according to some reports I received.
-Another one with bt878 suport 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:
-
-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:
-
- 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
-===================================
-
-If you are trying to make a new card work you might find it useful to
-know what the other elements in the tvcards array are good for:
-
-video_inputs - # of video inputs the card has
-audio_inputs - historical cruft, not used any more.
-tuner - which input is the tuner
-svhs - which input is svhs (all others are labeled composite)
-muxsel - video mux, input->registervalue mapping
-pll - same as pll= insmod option
-tuner_type - same as tuner= insmod option
-*_modulename - hint whenever some card needs this or that audio
- module loaded to work properly.
-has_radio - whenever this TV card has a radio tuner.
-no_msp34xx - "1" disables loading of msp3400.o module
-no_tda9875 - "1" disables loading of tda9875.o module
-needs_tvaudio - set to "1" to load tvaudio.o module
-
-If some config item is specified both from the tvcards array and as
-insmod option, the insmod option takes precedence.
-
-
-
-Good luck,
-
- Gerd
-
-
-PS: If you have a new working entry, mail it to me.
-
---
-Gerd Knorr <kraxel@bytesex.org>