Re: [Bluez-devel] Bluetooth headset problems.

[Max Krasnyansky <maxk@qualcomm.com>]

At 11:59 AM 7/6/2003, James Courtier-Dutton wrote:


>>I have made some progress. I can now record audio from the headset without it loosing any samples. I.e. I can record 8 bit PCM at 8000hz and it sounds fine. Before it was loosing samples and recording at more like 4000hz.
>>Once I get playback to work, I will post a patch to this list.
>>Cheers
>>James
>If anyone is interested, the fix for recording required 2 urbs for each isoc connection. The current cvs only uses 1 urb for isoc connections, so the usbcore fills one urb in real time, and then when it is full, sends it to hci_usb.c via a callback. Once hci_usb.c has finished with the urb it sends it back to the usbcore to get refilled. The problem is that while hci_usb.c is processing the urb, usbcore has no urb to put real time audio samples in, so it just drops them. If 2 urbs are used, if hci_usb.c is processing one, usbcore always has another to place samples in. As long as hci_usb.c does not hold on to it's urb for too long, all is ok. This fix was discovered by comparing the alsa snd-usb-audio driver with the hci_usb.c driver.
Make sense. 
So basically you're saying that you're just calling hci_usb_isoc_rx_submit() twice 
during open, right ? ie just like hci_usb_bulk_rx_submit() is called multiple times.

Max
        



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