faster PlayAtSpeed

Currently the transcription toolbar function PlayAtSpeed has a maximum value of 3X. My editing deck allows much higher multiples, I am used to searching raw data for “non-music” (speech etc.) and can recognize the difference at speeds between 7X and 10X.

If we look at the source code, AudacitySVNsrcwidgetsASlider.cpp, at or near line number 399:

      minValue = 0.01f;
      //maxValue = 3.0f;
      maxValue = 20.0f;
      stepValue = STEP_CONTINUOUS;

We see that changing maxValue from 3 to 20 seems to do the trick. I tested this and it seems to work just fine although speeds above 10X appear to be useless for my purposes.

Posting moved to Audio processing to retain the code - gist moved to Pending FRs on the Wiki