Hi,
I'm using an E-MU 0404 USB interface with the snd-usb-audio module from alsa 1.0.16, operating in isochronous asynchronous mode. This interface was producing very annoying click/pop sounds at regular intervals during playback. Eventually I discovered that the syncronisation mechanism telling the driver to send audio data faster or slower to match the interface's consumption speed does not work as expected, for some reason.
I did a very dirty hack within the source of this driver, simulating the interface asking for data to be sent a little bit quicker, and this almost fixed the problem *for me*. I really wish to debug this issue further, to find what actually does not work as it should in this feed-back mechanism. However this was the first time I dealt with alsa source code, so I do not have much experience. Therefore, I really need help with debugging this problem and maybe finding an universal fix.
Thanks in advance, Adi