Re: How can i configure bluez to transmit Voice over PCM

[Marcel Holtmann <marcel@holtmann.org>]

Hi Sebastian,

> i'm using bluez 3.36 on an embedded system with a CSR Chip connected.
> Communication via HCI over UART works well. I need to receive and send
> voice from/to a headset and therefore I want to send/get the voice as
> PCM to the CSR chip. The PCM pins of the CSR Chip are connected to the
> SSC pins of an avr32 microcontroller. The CSR chip is configured to use
> PCM as soon as the Host produces Clock, otherwise it tries to transmit
> voice per HCI which is too slow (only 115200 baudrate for a 8kHz PCM
> stream).
> In etc/bluetooth/audio.conf I have set SCORouting=PCM
> In etc/Bluetooth/asound.conf I have written the following:
> #####################
> pcm.headset {
> 	type bluetooth
> }
> ctl.headset {
> 	type bluetooth
> }
> #####################
> But bluez is still sending voice over HCI, which is ok because: How
> should it know where to transmit the PCM stream. I need a device but I
> am not sure what exactly is needed.
> Do I have to write a dummy soundcard driver which only sends and
> receives pcm over the ssc pins? I guess a pseudo UART device for SSC
> isn't enough because bluez needs an alsa device, correct?
> 
> For a quick and dirty solution: Is it possible to let bluez reduce the
> soundquality so it works over HCI any way?
> 
> Are my settings correct or have I missed something?

I would really advise you to start using 4.27 instead of a previous
major version that is not developed.

Also when using PCM for SCO then you need to use the D-Bus API for
headsets and not the ALSA plugin.

Regards

Marcel