Generated MIDI file deltaTimes
Hi,
I'm noticing a kind of an odd thing with a MIDI file generated from a score: the delta times seem to be one off. Here's what I mean:
Say I have a score with a line that starts with a half note and then a quarter note. With the PPQN=480, I would expect the following basic sequence of events:
| delta time | event |
|---|---|
| 0 | NoteOn, velocity X |
| 960 | NoteOn, velocity 0 |
| 0 | NoteOn, velocity X |
| 480 | NoteOn, velocity 0 |
Instead, I see something like the following:
| delta time | event |
|---|---|
| 0 | NoteOn, velocity X |
| 959 | NoteOn, velocity 0 |
| 0 | NoteOn, velocity X |
| 479 | NoteOn, velocity 0 |
This probably doesn't make much difference for playback of the MIDI file (it being only a difference of 1/480th of a quarter note), but I'm trying to write a program that parses MIDI files, and it's kind of choking on the off-by-one errors. I looked at some other MIDI files around the web, and they seem to have the sort of delta times I would expect.
Is this intentional? If so, can someone explain the rationale?
Comments
I think it is on purpose, to avoid cases where some implements respond poorly to the note off and subsequent note on happening on the same tick. I recall complaints in particular about pedal events causing trouble for some sequencers or synths.
I just made a test for my curiosity and shared the result, maybe it's useful for someone:
I did made a test with the free MIDI editor Sekaiju and I saw the following command might be useful:
"Modify Events Duration", Relative ticks, 1 (It simply adds 1 tick to all note values.)
Although it requires an extra step in your work.