#1391 MIDI Recording, High CPU Usage

[Ted Felix]

Two scenarios still result in high CPU usage while recording MIDI:

1. Recording for a long period of time. The CPU usage goes up gradually.
2. Recording past the end of composition. The CPU usage quickly jumps to 100% on a core. Fixed in [#1407].

See also:
[#1350] Can't Record Beethoven
[#1193] MIDI notes dropped when recording

[Ted Felix]

Two key problems remain:

1. The change notifications from Composition and Segment are far too frequent when recording, and the observers do far too much work.
2. CPU usage gradually increases when recording due to the generation of notation previews which take longer and longer to generate as more and more notes are recorded.

[Ted Felix]

Huge strides have been made here, but much work is still left to be done. This will probably be open forever and never "completed".

CompositionView is the next place to focus. Given a one hour long piano practice session (and I'm not very good), this slows to almost a complete halt on my machine. The code that renders the segment previews needs to be disableable in case a long recording is anticipated. That should be a simple workaround for now. Then we need to make the notation preview generation simpler and faster. Might want to look at how Ardour or some other app handles this and imitate.