Comment 3 for bug 1117806

Daniel Schürmann (daschuer) wrote :

I have tried to nailed it down for X11:

For a super smooth waveform scratch we need a constant mouse sample rate, best at audio buffer size.
All X11 mouse events are timestamped, so in theories we could achieve this with X11.

Unfortunately the mouse is handled by Qt in the not real time GUI Thread and the time stamp is lost on the way to mixxx. So we may facing unknown but significant delays if Mixxx is busy with other tasks in GUI thread.
An other problem is, that there is no MouseStop event. We are not able to distinguish mouse movement stops from delayed MouseMove event.

I think a solution for now is to calculate the missing samples from the previous rate for about 23 ms. The resulting overshoot in case of stops or rate decrees should be ironed out by the following velocity controller.