Bluetooth-alsa Project

   This project provides a way to use a bluetooth headset with Linux. We
   do this currently by making an alsa kernel driver which uses bluez to
   reach the headset. It works well enough now to get voice-quality audio
   to and from most headsets. We've had success with:
     * BlueTrek 1, G2
     * Bluetake iPhono BT420 (using either sco or a2dp)
     * Canyon CN-BTH1 (must click headset's volume-up button after each
       connection)
     * Ericsson HBH-60, HBH-35
     * Ericsson HBH-PV700 (headset may go silent after a few minutes)
     * iTech Clip S (using either sco or a2dp)
     * Jabra BT110, BT130, BT200, BT250
     * Jabra Mega BT (use -r option to reconnect rfcomm channel whenever
       it's lost)
     * LevelOne BLH-1000 (occasional noisy connections)
     * Logitech HS01 (has a noisy microphone?)
     * Logitech Mobile F-0179A, Mobile F-0228A
     * Motorola HS801 (volume must be changed from headset?)
     * Motorola HS805 (had to uncomment "auth enable" in
       /etc/bluetooth/hcid.conf and restart first)
     * Motorola HS810/HS850 (may work "better" if you manually specify
       the handsfree channel, 8)
     * Motorola HT820 (for both sco and stereo; sound crackles a bit)
     * Nokia HDW-2, HDW-3, hs-11w
     * Plantronics M2500
     * Siemens HHB-600

   We currently don't have any code to make the connection to an audio
   gateway (typically a cellphone). There's a [1]project associated with
   asterisk and a [2]standalone app for using a cellphone.

  Features

   We have code to make a headset connection (using the btsco daemon) to
   send audio through the alsa system and we have separate code to send
   stereo audio to the a2dp device using a userspace program (a2play).
   Only a couple of headsets can accept stereo audio so try the btsco
   stuff first.

  Build

    1. Install or update the required packages:
          + automake-1.7
          + libbluetooth-dev (aka libbluetooth-devel or bluetooth-devel
            or bluez-libs)
          + libasound2-dev (aka alsa-devel)
          + a recent (2.6.11.7 or newer) kernel with *integrated* alsa
            enabled (it won't work with the "standalone" alsa drivers
            that are a separate download from the kernel)
    2. Check btsco out from cvs:
        cvs -d:pserver:anonymous@cvs.sf.net:/cvsroot/bluetooth-alsa login
        cvs -d:pserver:anonymous@cvs.sf.net:/cvsroot/bluetooth-alsa co btsco
    3. Compile:
        ./bootstrap
        ./configure
        make
        make install
        make maintainer-clean
    4. For SCO (two-way voice quality audio) you need a kernel with the
       emu10k1 driver selected (this is one of the drivers that forces
       the inclusion of the implementation of "snd_hwdep_new"). Build the
       kernel module:
        cd kernel
        make
        make install
        depmod -e
        make clean

  Using SCO audio

    1. insert the module (or better, set up the alsa configuration to
       load it)
        modprobe snd_bt_sco
    2. stop the esound controller if it's running via
        esdctl stop
    3. run
        hciconfig hci0 voice 0x0060
    4. turn on the headset (you may need to prepare the headset to be
       paired the computer, usually by turning on the headset and holding
       the on button until it beeps; make sure the headset has not
       connected to your cell--this would block the computer's
       connection.)
    5. run the handler (let it keep running if you run in the foreground)
        btsco bdaddress
    6. You probably need to enter the passkey if it's the first time
       'round
    7. send and receive audio from the headset (usually using /dev/dsp1)
       or via the alsa device with something like
        aplay -B 1000000 -D plughw:Headset sound.wav

   Right now the daemon interaction is somewhat limited:
     * Put alternating lines of regexes and shell commands in ~/.btscorc
       and when something that the headset sends matches these regexes,
       the shell command is run (with any back references \0 \1 etc
       replaced from the regexp, \s replaced by the link state and \p
       replaced by the daemon's pid). This, of course, is primarily
       intended to "do stuff" when the headset button(s) are pressed.
     * Send SIGHUP to the userspace program to make it re-read the config
       file.
     * Send SIGUSR1 to the userspace program to make the headset ring.
     * Send SIGUSR2 to the userspace program to force a headset
       reconnect.

   Andreas Beck contributed a .btscorc and skype script for making the
   headset button answer an incoming call. It's in our contrib/ dir and
   he may have updates [3]here.

  Stereo (A2DP) Streaming

   A2DP provides a way to send stereo high-quality audio to some of the
   newer headsets. On all the headsets I've seen so far, this is one-way
   audio, so if you were expecting to get something like a gaming headset
   (talking to other players, getting stereo sound back from the game),
   you should wait for the next generation of headsets to get 2-way A2DP.

   Right now A2DP transmission requires a helper app to bring in audio.
   Hopefully we can remove this requirement. From the btsco directory
   after a successful make:
        mpg123 --au - file.mp3 | ./a2play 00:0D:3C:30:32:AD

   Where you replace file.mp3 with a good mp3 file and bdaddr with the
   address of your headset. If you have trouble with using a2play, let us
   know on the mailing list if this works for you instead:
        mpg123 --au - file.mp3 | sbc/sbcenc - | ./sbc/rcplay 00:0D:3C:30:32:AD
-

   You can send live audio from line-in etc using a command like:
        ./a2play -s -d -r 44100 00:0D:3C:30:32:AD /dev/dsp

   Don't be surprised to get a delay. It's probably under 500ms but not
   much under that.

   The A2DP sink code receives a stream from another device. Run it with:
        hciconfig hci0 class 0x200404
        sdptool add A2SNK
        ./a2recv

   It will try to bind to the bluetooth adapter and send audio out to
   /dev/dsp.

  Embedded status

   The status of work on gumstix/xscale is on its [4]own page.

  A2DP userspace plugin

   If you want to experiment with the alsa userspace plugin work, go to
   the directory 'alsa-plugins' in the cvs archive and have a look at the
   BUILD docs there. This lets you have alsa clients such as xmms send
   audio directly to an a2dp headset.

  Links

     * [5]Bug list at sourceforge
     * [6]Bluez main page

  Discussion

   This code is experimental, so the best place to talk about it and
   submit changes is on the bluez-devel mailing list.

   If things aren't working as you expect, some of the things that can
   help us track it down are:
     * Whether there is a hub between your computer and bluetooth adapter
       (you should avoid this [7]especially if it's a usb 2.0 hub)
     * Manufacturer and model of headset and bluetooth adapter
     * Output from hciconfig -a
     * Output from hciconfig hci0 revision (Run hciconfig as root) 
          + If it prints "SCO mapping: HCI" then your adapter should
            work.
          + If it prints "SCO mapping: PCM" then you might permanently
            change the setting using a command like "pskey mapsco 0"
            using bluez-utils-cvs but this is at your own risk.
          + If it doesn't print either of those, you probably need a
            different bluetooth adapter (preferably "CSR" based). You
            might be able to get a broadcom adapter to work if you apply
            a [8]patch to force sco mtu values (eg works for F8T012; let
            us know how it works on bluez-devel!)
     * Output from hcitool info bdaddr where bdaddr is the headset's
       address
     * Output from hcidump -X while running btsco or a2play if
       appropriate
     * The output btsco -v or a2play prints to the screen
     * Your kernel version and bluez userland versions or distro
     * Result when trying it with a recent kernel if possible (eg 2.6.11)
     * If you have a headset that can do a2dp, try both btsco and a2play
       (the significance is that the latter does not use SCO)
     * If you can try another bluetooth adapter or headset, let us know
       if that helps (the adapters are cheap now, eh? :)
     * If you can't pair or connect with the headset, did you pair it
       with another device? Did it help to reset the pairing by removing
       /etc/bluetooth/link_key or
       /var/lib/bluetooth/[dongleaddr]/linkkeys or by putting the headset
       in pair mode? You may have to redo this often if you try to
       dual-boot windows or if you use the same dongle on another
       computer. Be sure to set "auth disable" and "encrypt disable" in
       /etc/bluetooth/hcid.conf.

  Credits

   Some instrumental people in this effort:
     * [9]Jonathan Paisley (retired from the project) started it up and
       wrote much of what we have now
     * [10]Niko Berger brought the patches forward to 2.6.7 and 2.6.8
     * [11]Lars Grunewaldt (also retired) added some stuff to the
       userspace daemon
     * [12]Marcel Holtmann has always been the key developer for bluez
       and has recently jumped in and helped a lot with our project
       specifically
     * Henryk Ploetz completed the first SBC codec
     * [13]Brad Midgley is doing documentation, A2DP protocols, vendor
       relations, and project coordination
     * Fredrik Tolf has been fixing up daemon/userspace interactions
     * Mayank Batra contributed a2recv.c for A2DP sink support
     * Victor Shcherbatyuk added fixed-point A2DP encoding including Arm
       optimizations
     * Andreas Beck gave us the script in contrib for skype and is
       working on automatic mic gain and fixing noise

  Our Sponsors

   [14][gumstix.gif] 

   Gumstix provides brilliant embedable xscale boards with bluetooth
   [15]SourceForge.net Logo 
     _________________________________________________________________

   The [16]bluetooth-alsa project pages

References

   1. http://www.crazygreek.co.uk/content/chan_bluetooth
   2. http://www.soft.uni-linz.ac.at/_wiki/tiki-index.php?page=ProjectBluezHandsfree
   3. http://www.acs.uni-duesseldorf.de/~becka/download/skype/
   4. http://bluetooth-alsa.sourceforge.net/embed.html
   5. http://sourceforge.net/tracker/?group_id=116589&atid=678258
   6. http://www.bluez.org/
   7. http://sourceforge.net/mailarchive/message.php?msg_id=11431438
   8. http://bluetooth-alsa.sourceforge.net/sco-mtu.patch
   9. http://www.dcs.gla.ac.uk/~jp
  10. http://www.gargan.org/
  11. http://www.dark-reality.de/
  12. http://www.holtmann.org/linux/bluetooth/
  13. http://www.xmission.com/~bmidgley/
  14. http://www.gumstix.com/
  15. http://sourceforge.net/
  16. http://sourceforge.net/projects/bluetooth-alsa/