[Bluez-devel] usb/sco problems

[Bluez-devel] usb/sco problems

[Victor Shcherbatyuk]

Hello Marcel,

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?

Regards,
   Victor.
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Re: [Bluez-devel] usb/sco problems

[Marcel Holtmann]

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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