#1802 Apparent MIDI audio delay caused to new jack logic

[musewhirl]

I've been trying to reproduce this bug for weeks now, and it was infuriating not being able to pin it down due to its apparent random nature. But I think I've finally got it, and definitely tied it to the new jack logic. It seems to be a MIDI version of the audio bug #1792, which itself was just as difficult to reproduce.

Basically, I observed that sometimes when I play a composition starting at some random location on the timeline, then hit stop following by play again, I hear extra notes, sometimes from many instruments on different tracks, that should not be there completely ruining the composition, but only for a brief time. If left to play on, it seems to recover with a few measures, although if recording, you would be stuck with the broken audio. It does not always occur, even when I return to reproduce the error. Instead, it's randomly at a later time and different place.

Anyway, all I can do here is present a much simplified case where there is a definite inconsistency of behavior, which might be the basis of the problem.

Steps to reproduce for non-percussion notes:

1. Check the boxes in preferences to "Use Jack Transport" with the new logic checked
2. Create a non-percussion MIDI track and an instrument that will sustain for at least a whole measure (e.g. Piano with do)
3. Create a one-measure segment
4. Open MatrixEditor on the segment and create one whole note
5. Ensure a good view of whole note on the screen
6. Place playback pointer at start of note
7. Hit Enter key to play followed by same key to stop, regularly at about once per 1/16 or 1/32
8. Obviously the note always sounds at the start of the note
9. However, for the subsequent starts in the middle of the note, sometimes audio is heard, while other times it is not
10. Now try and arrange for one of the plays to be of the silent type, and let note run to its end
11. In my case, if I start one of the silent variety prior to the mid-point of the note, then right at the mid-point, I then hear the note out of the blue!
12. If all of the above is reproducible, simply turn of the new jack logic checkbox to prove that the problem goes away too

Hence, it sounds like a delay of the start of the note, much like bug #1792, since there is no new note at the point when it's heard. I don't know if the delay is from the start of the note, or the middle of the note when the silent hit occurred.

But the obvious question is even if the audio was consistently heard, i.e. no a delay, should the MIDI note be sent if play was hit in the middle of the note? The MIDI event for the note is located at the start of the note, along with its duration, but that is behind the subsequent starts in the middle of the note? The answer to that boils down to what is the expected norm for a sequencer? But this bug is more concerned with the inconsistency, which leads to apparent random behavior in more complex compositions.

[Philip Leishman]

I cannot reproduce this. When you say the play is of the silent type - do you mean the track is muted ?
Is the track talking to an external midi instrument or is it using a plugin to create the sound ?

[musewhirl]

When you say the play is of the silent type - do you mean the track is muted ?

No, this does not involve muting. I mean two things can happen as you do this rapid play-stop-play-stop etc.

1. On the first play at note start, you hear audio both with and without the new logic
2. On a later play in the same rapid sequence, you don't hear audio (the silent type of play), when using the new logic. With the old logic you always hear audio.

It actually doesn't even have to be that rapid a play-stop-play, so long as you can get a few plays within the whole note. I did it with 70 bpm easily. But try:

1. Slow tempo down to 10, then you have all the time in the world for your whole note :-)
2. I used a piano note, but it doesn't actually matter if you use percussion notes or not, since a single percussion note defaults to a whole note anyway and has the same behavior
3. FYI: I observed using the MatrixEditor with Grid 1/64 zoomed so I could see the whole note
4. Make sure you use jack and also have the new logic checked
5. Also I happen to have RG create audio inputs and outputs, but not set to start jack
6. Hit play-stop-play at around one to two times per second, listening for when you hit play and hear no audio
7. Although difficult, if you hear no audio on a play don't hit stop...do nothing and just wait to see if the audio is delayed and played later
8. Now just turn off the new logic and repeat

Is the track talking to an external midi instrument or is it using a plugin to create the sound ?

It's an external keyboard, but I am certain that doesn't matter.

[Philip Leishman]

I still can't reproduce this. Difficult to explain how it could happen.
Can anyone else reproduce it ?
Any suggestions ?