[Bluez-devel] Thoughts about AVDTP support

[Marcel Holtmann <marcel@holtmann.org>]

Hi Folks,

I think one of the next major goals of BlueZ should be the support of
the Audio/Video Distribution Transport Protocol (AVDTP). So I spent some
time in reading the protocol specification. The specification is very
complex and I think most of the products will only support the basic
mode with signal and media channel. However it took me some time to
realize that they are using multiple L2CAP channels between two devices
with the same PSM. I never thought that this was possible, but our L2CAP
core already supports such configuration. Now I asked myself, why HID
and HCRP needed two different PSM values?

To be capable of handling multiple audio and video streams nicely, I
think we need to implement AVDTP as a kernel module. In that case we can
make use of two different interfaces to AVDTP. One for the A2DP support
that is directly connected to ALSA and the second should be a simple
socket interface. I am no audio/video streaming expert, so what socket
type is the best for this case?

Before I start writing any source code, I would like to get my hands on
a product that already uses AVDTP. I need to know what parts of this
protocol are in use and how they handle it. Searching for an end user
product I found one from Air2U (www.air2u.com.tw). The german reseller
is Aiptek and they call it BT MusiCool 300

	http://www.aiptek.de/index.php?mapid=31&katid1=4&detailid=11

I asked them to donate one of these to me, but they said no. Actually
not a nice company. Searching a little bit more I found out that Amazon
is selling it for 99 EUR. This is fair price for two Bluetooth devices
(SNK and SRC), but I decided not to buy them. My conclusion was that if
I should really start working on AVDTP, someone else should buy me an
end user device for testing any of my code. However there is always the
possibility to donate money (www.bluez.org/sponsors.html) which I can
use to buy unsupported hardware.

Regards

Marcel




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