Bluetooth Headset - Voice Commands

Mike Hodson mystica at
Thu Mar 1 05:47:28 CET 2007

On 2/28/07, Jonathon Suggs <jsuggs at> wrote:

> The reason that I ask is that on my PocketPC phone (iMate PDA2K), there
> is supposedly a hardware limitation that will not allow for this to
> occur.  It can have the bluetooth headset button initiate the program,
> but it cannot use the bluetooth headset to transfer the audio to the
> program.  It has to use the built-in microphone for routing audio to the
> voice command software.  I don't remember specifics, but I think it was
> because the bluetooth module tied to the gsm module in hardware or
> something along those lines.
> All of that to ask, is the bluetooth implementation on this device going
> to have that same limitation?  I was looking through the wiki and
> noticed the bluetooth is connected to the USB Host I am
> hopeful it won't suffer the same limitation.

I'm going out on a limb here and hypothesizing again, however it may
shed some light:

My understanding of how the OpenMoko software stack works, is that it
will be using some a software audio routing interface, either direct
ALSA or gstreamer (tied into ALSA as the audio access method). The
audio can go between the mic/speaker thru the wolfson codec, or you
can  switch it to the bluetooth device.

By being connected to the USB bus, this works exactly like every
current Linux computer with bluetooth: as of now, the BlueZ stack can
do SCO / headset, and they are working daily on properly working A2DP
(advanced audio) stereo codec support both as alsa modules.  It would
then be my guess, that all the OpenMoko software would have to do, is
change the alsa input/output by responding handsfree button or avrcp
commands (for stereo headsets).

Furthermore, it is definitely plausible that the bluetooth controller
in your pocketpc is somehow intertwined with the GSM chipset.  If this
chip has no provision of routing audio into the software, and only
considers bluetooth a voice service, then it would talk directly to
the wireless interface and its GSM chip. The windows mobile/ppc
software can't grab it.

Please keep in mind, this is speculation, however knowing how my
linuxbox works with bluetooth audio is the background for my educated
guess :)

The pocketpc routing is probable, but again speculation. If I'm wrong,
please let me know :)


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