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[Linphone-users] Latency with Bluetooth headset

From: Sybren Stuvel
Subject: [Linphone-users] Latency with Bluetooth headset
Date: Thu, 24 Nov 2005 09:51:05 +0100
User-agent: slrn/ (Debian)

Hi all,

I'm having a latency of 2 to 3 seconds using Linphone 1.1.0. To test
this, I've set up an Asterisk server on my LAN, running an echo test.

My setup is as follows: I'm using a bluetooth (BT) headset (Bluespoon
AX) connected to a BT USB stick. It's presented to the system as an
extra sound card, using bluetooth-alsa. It works with both ALSA and

Every time a program is using this "sound card", my computer
reconnects to the BT headset, and as soon as sound is no longer used,
it disconnects again. Creating this connection takes a few seconds,
and I think that this is the source of the delay. If I replace the
audio-out with a regular headphone, the delay is cut in half. If I use
a regular microphone as well, the delay is reduced to half a second.

Still, this delay of half a second is about 0.2 seconds longer than
the delay that KPhone gives me. Ordinarily, I'd say "just use KPhone
then", but the problem with KPhone is that it doesn't support RFC2833
DTMF - just inband. Inband DTMF only works with alaw and ulaw, but I
want to use the GSM codec, so KPhone isn't really an option.

The problem with the world is stupidity. Not saying there should be a
capital punishment for stupidity, but why don't we just take the
safety labels off of everything and let the problem solve itself? 
                                             Frank Zappa

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