Hello, I am still working on module-loopback and hit a problem that I cannot explain. When running a HDA card with long latency (333ms) I see that the resulting latency is not stable but varies around 300 usec. What is worse, the changes in latency are not even reported, module-loopback sees a completely stable value ( +/-10 usec). My setup: I have a bitscope dual channel USB oscilloscope attached to another machine. This device also has a function generator that I set to 1kHz rectangle. The signal is input to the HDA card and fed to the output of the same card via module-loopback. Input and output signal are measured using the oscilloscope. The movement of the edge of the output signal now shows the "latency jitter" which can be made visible by using the overlay mode of the oscilloscope. The result for HDA (module-loopback running with 500ms adjust time and 1s latency) is shown at http://georg.chini.tk/hda_333ms_3.png. Some of the original input signal is somehow fed into the output signal, don't know where this happens, so please ignore it as it has no impact on the result. At the bottom you see the input signal with a completely stable edge. On top there is the output signal. You can see that the latency of the output signal is spread over 300 usec with a spacing of a quarter of the sample time. Module-loopback is doing no regulation at all because - as said above - it does not see those latency changes. For small latencies (20ms and smaller) I still see a double line. For USB devices the effect is much worse, but difficult to demonstrate because USB devices are less stable anyway and module-loopback's regulation spoils the effect. Does anyone have an idea why this happens and if it is a problem of pulseaudio or of the alsa driver? I think it is pulseaudio, because with zitaj-bridge and Jack I only see a single line. Regards Georg
