[Bluez-devel] Re: Headset via usb dongle devel problems.

[Jonathan Paisley <jp-www@dcs.gla.ac.uk>]

On Fri, 11 Jul 2003 18:53:31 +0100, James Courtier-Dutton wrote:

> I have discovered that the performance of the bluez stack is a problem
> when using the hci_usb.c driver.
> I cannot get it to send SCO packets quicker than one urb per 40ms. As
> the headset needs one urb per 3ms, this is quite a problem. I would also
> assume that other applications like file transfer over bluetooth would
> be bad.

Have you identified what's actually causing this rate limit? It sounds
more like a scheduling issue to me than a number-of-memory-copies problem.

Would you consider sharing the code modifications you have made thus far?

I have been experimenting with two USB dongles with the aim of making the
PC act as a headset (I don't have one). I have been able to get reasonable
(although sometimes choppy audio) on the PC. That is, the sound is being
received by the PC. I haven't yet managed to test sending audio except for
/dev/zero. All this testing is with 2.4.20-mh10.

The two dongles I have are the Mitsumi WIF-0402c and the Sitecom CN-500,
which report as follows:

Sitecom CN-500:
$ sudo /sbin/hciconfig hci0 revision
hci0:   Type: USB 
        BD Address: 00:10:60:A2:E4:C2 ACL MTU: 192:8  SCO MTU: 64:8
        HCI 16.4
        Chip version: BlueCore02
        Max key size: 56 bit
        SCO mapping:  HCI

Mitsumi WIF-0402c:
$ sudo /sbin/hciconfig hci0 revision
hci0:   Type: USB 
        BD Address: 00:A0:96:1D:4A:AA ACL MTU: 128:8  SCO MTU: 64:8
        HCI 11.2
        Chip version: BlueCore01b
        SCO mapping:  HCI

The Mitsumi accepts the SCO connection and then gives up, whereas the
Sitecom is able to sustain the connection for as long as I have tested
(<2minutes). The Mitsumi is much older, so I'm not surprised there are
problems. However, both devices work okay in this manner under Windows.





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