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Subject: How can i configure bluez to transmit Voice over PCM
Date: Fri, 30 Jan 2009 11:39:28 +0100
Message-ID: <49ED01FC03EE524BB7BB258E8F93BFF32F3DB5@bfl-exchange-1.BFL.local>
From: "Matuschka, Sebastian" <Sebastian.Matuschka@gcd-solutions.de>
To: <linux-bluetooth@vger.kernel.org>
Sender: linux-bluetooth-owner@vger.kernel.org
List-ID: <linux-bluetooth.vger.kernel.org>

Hi,

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 know that version 3.36 is a bit old but it works perfectly for me.
Thanks and Best Regards
Sebastian