Listening to MIDI Machine Control messages [welcome for testing]

[Igevorse]

MIDI Machine Control (MMC) is a feature that helps to control playback of MuseScore via MIDI by sending special MIDI messages.
For now MuseScore is able to listen to this messages, not send them.

New opportunities unlocked:

• Synchronize MuseScore with software that doesn't support JACK Transport
• Control playback of MuseScore even without JACK

Supported events:

• System realtime messages:
  • Start (0xFA)
  • Stop (0XFC)
  • Continue (0xFB)
  • Song Position Pointer (SPP) (0xF2)
• System exclusive (SysEx) messages: (0xF0 0x7F <deviceID> 0x06 <command> 0xF7)
  • Stop (command: 1)
  • Pause (9)
  • Play (2)
  • Deferred play (3)
  • Rewind (5)
  • Goto/Locate (0xF0 0x7F <deviceID> 0x06 0x44 0x06 0x01 <hr> <mn> <sc> <fr> <ff> 0xF7)

It works with:

• JACK MIDI
• ALSA MIDI
• PortMidi (partially)

Events that are not supported for PortMidi:

System exclusive messages

UI changes:

• "Accept MMC messages" checkbox in Preferences->I/O
• Combo box for selecting Device ID

Tips

• Since MuseScore is a note editor/engraver, it's better to use SPP message instead of Goto/Locate. SPP operates with MIDI beats while Goto/Locate with time in seconds/frames.
• Use small MIDI buffer to minimize the delay between applications. For JACK it is 64/128 samples. Using "ALSA Raw-MIDI" MIDI driver instead of "ALSA Sequencer" reduces the delay twice.
• Not all sequencers can handle MIDI realtime messages in real time, so if you want to seek/locate while playing it's better to stop playback, seek and play again.
• There is no restriction on using MMC with JACK Transport, but you can get a delay or other surprises.

Welcome for testing!

[Jojo-Schmitz]

rebase needed...

[Igevorse]

@Jojo-Schmitz rebase is done.

[Jojo-Schmitz]

unfortunatly another rebase is needed

[dmitrio95]

Archiving this for now, feel free to reopen if there is an interest in adding this feature.