Playback data tracking

Playback provides a way to track some MIDI data to correctly handle jumps in time and get properly sounding data. There are two main groups of data to track:

• notes
• MIDI parameters (pitch bend, program, control value)

Notes tracking

Let's take a look at the following events sequence to play:

Playback class has TrackNotes property. If its value is true, playback will internally construct notes based on input objects to play. So in our example one note will be constructed:

Now let's imagine a playback's time is at some point and we want to jump to a new one (with MoveToTime for example):

If we now jump to a new time that falls in the middle of the note, behavior of the playback will be different depending on TrackNotes property value. In case of the property value is false nothing special will happen, just the current time of the playback will be changed. But if we set TrackNotes to true, new Note On event will be generated and played when we jump to the new time:

The same situation with opposite case:

So we want to jump from the middle of a note to the time after the note. As in the previous example, if TrackNotes is false, just the current time of the playback will be changed. But if in case of true, a new Note Off event will be generated and played when we jump to the new time.

So TrackNotes = true tells playback to track time jumps when the current time pointer of the playback either leaves a note or enters one to finish or start the note correspondingly.

Of course in cases like this:

playback will play both Note Off event (since we're leaving the first note) and Note On one (since we're entering the second note).

MIDI parameters values tracking

Let's imagine we have the following events sequence to play:

And now we want to jump from the current time of a playback to a new time (with MoveToTime for example):

So by the current time A event is played and the current program corresponds to A. If the playback just changes the current time, the note will be played using program A which may be wrong since the note is actually under B program influence.

To track a program, Playback class has the TrackProgram property. If it's set to false, nothing will happen except changing the current time. All following notes can sound incorrectly due to possibly skipped program changes.

But if we set TrackProgram to true, playback will play the required Program Change event immediately after time changed. So in our example B will be played and then playback continues from new time:

Program tracking works in opposite direction too of course:

We have program B active at the current time. But when we jump to a new time (before B but after A), A event will be played.

Playback can track at now three MIDI parameters:

• program;
• pitch bend;
• control value.

We have discussed program tracking above. But tracking the remaining two parameters is absolutely the same. To track pitch bend value there is TrackPitchValue property. To track control value there is TrackControlValue property.

Of course all these parameters are tracked separately for each MIDI channel and in addition to this control value tracked separately for each control number.