GSoC 2016 - Week 8 - Performance and Preferences

This was my eighth week working on note entry with MuseScore for Google Summer of Code. I made rapid progress implementing a working proof of concept early in the project. For the past couple of weeks I have been going back over my previous work, improving the structure and performance of the code, and giving users more control over note entry via additional options and preferences.

This week’s summary:

• Improvements to Automatic Real-time note entry mode:
  • Improved performance
  • Auto-advance triggered when a note is pressed
• New options in preferences:
  • Configurable input tempo/delay for Automatic Real-time
  • Set MIDI key/pedal for advancing in Manual Real-time mode
  • Choose whether to advance again when the key is released
• Improved code structure

Still to do:

• Configuration options for the metronome
• New implementation of rhythm simplification and voice extraction

Automatic Real-time mode

This is supposed to be the mode where the user plays the piece at a constant tempo, but my initial implementation had a few performance issues that meant the tempo was not quite constant. Pressing lots of MIDI keys at once would cause the beat to arrive very slightly late, but enough for it to be noticeable and off-putting. My algorithm was supposed to account for the time needed to add the notes to the score, but it wasn’t particularly effective. My new algorithm is much simpler and does this more successfully.

function automaticRealtime() {
    int realtimeDelay = 750; // milliseconds
    while(true) {
        timer.start();
        advanceAndAddNote(); // This is an expensive function
        timer.stop();
        int delay = realtimeDelay - timer.elapsed(); // ensure loop always takes 750ms
        sleep(delay);
    }
}

It is also possible that my structural improvements have helped here too by reducing the overhead associated with adding notes, or perhaps another developer has made some improvements to efficiency elsewhere.

Simply entering automatic real-time mode does not cause the score to start advancing. Previously the advancement could only be triggered by pressing a special key or foot pedal - the same as is used in manual real-time. (The difference between the modes is that in manual real-time the key must be pressed repeatedly whereas in automatic real-time it only needs to be pressed once,) This system works well providing the user has a pedal or other suitable control. Since this is not always the case I have added a second way to trigger advancement. The new method is simply to start playing notes - automatic advancement will continue until the user stops playing notes. As a consequence of this it is not possible enter rests when using automatic real-time in this way, but it is still possible to add rests if the pedal is used.

Options made available in the preferences

I have added three new note entry options to the preferences to allow the user to adjust:

• the delay in automatic Real-time mode
• the MIDI key or pedal used to advance in both Real-time modes

• whether releasing the advance key also triggers an advance in the same way that pressing it does. This is useful when entering quavers / eighth notes in a score that has a 4/4 time signiture (based on crotchets / quarter notes).