Re: [Bluez-devel] usb/sco problems

Marcel Holtmann
2005-07-18T09:06:02Z

Hi Victor,

> I have a small app which routes back sco data received from a
> headset, so basically you supposed to hear yourself back in the headset.
> It works fine with the voice setting 0x0060, but when I switch to u-law
> 0x014c sound is starting to break out, if I run the program on arm using
> uart it works fine for both of the settings.
>
> Using hcidump shows a regular pattern of sco receives/sends (normally like
> 3 packets in, 3 packets out, which is probably the result of usb buffering
> for incoming packets), but if I look at the output of an air-sniffer, I
> see that the data sent back to the headset has very
> irregular time pattern (a lot of transmissions are missing), while the
> time pattern of incoming data from the headset is ok.
> So it looks like something goes wrong after the sco data is supplied to
> the hci_usb. I have this problems with 2 dongles I have (BC4 and
> Broadcom built-in in my laptop), so does not look as a dongle problem. Any
> idea what might be wrong?
>
> Well, I also have a app which does copying data received from a phone
> sco to a headset sco and back (2 sco channels open and app functions as a
> middle agent). This app is also working for arm via UART, but not on my
> laptop (and home pc) via usb. The question does any1 has a successful
> example of having 2 sco channel open (to different devices) at the same
> time?

for USB you need to set the correct alternate setting for the SCO ISOC
endpoint. This should be done automaticly, but at the moment this is a
static module parameter called "isoc". Look at the specification on how
to calculate its value depending on the number of SCO connections and if
they are 8-bit or 16-bit. The default value is 2, which means one SCO
connection with 16-bit (aka voice setting 0x0060).

Regards

Marcel

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