Adrian Stancu wrote:
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.
The momentary frequency as requested by the device is shown in /proc/asound/card?/stream? (if CONFIG_SND_VERBOSE_PROCFS is enabled).
Try something like:
while sleep 0.3; do grep "Momentary freq" /proc/asound/card0/stream0; done
In theory, once the device has determined its own speed relative to the computer, this value should be nearly constant. (When a stream has just been started, the requested frequency usually is higher because the device's buffer is empty.)
Regards, Clemens