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Old 10-01-2020, 04:16 AM   #1
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Default [6.36] regression bug when loop recording a midi item

2021.9.17 : Title used to be "PDC makes wrong punch-in/out timing when time-selection auto punch". Look at near the bottom to see the new regression bug https://forum.cockos.com/showpost.ph...8&postcount=13

  • In the time-selection auto punch mode, Punch-in/out's timing works wrong -- it gets late -- for a track with a non-zero pdc
  • In the auto-punch selected items mode, punch-in gets its timing right, but the punch-out gets late still. Hence, the next coming part is truncated and becomes short.
  • It aggravates with midi items but audio items have issues too
  • You can turn off PDC entirely, but it won't sync with other tracks then
  • This issue has been there for years, and it's there with the most recent reaper versions.


Have a look at this video recording:

Steps to reproduce the bug:
  1. Create an empty track with an empty MIDI item two-bar long, which starts from 3.1.00.
  2. Draw some midi notes on both the bars
  3. Add a VSTi with a sample buffer larger than 0 (or you may just add reafir)
  4. Time select the second bar only
  5. Set the recording mode to time selection auto punch
  6. Move the cursor to the beginning of the first bar
  7. Hit record
  8. You can hear the first note of the second bar is played briefly. Otherwise, you may add ReaControlMIDI to see the MIDI log at the track fx.

I've set a time selection to re-record, exactly from the start of a bar to the end of the bar. The recording mode is set to "time selection auto punch". All the notes are quantized to the grid.

Now when I hit the record button, the first bar(C D E, that is MIDI notes 48, 50, and 52) plays, and when it gets to the second bar, the initial recording's first note(MIDI note 48) is played for a short time(for 4ms between NOTE ON and NOTE OFF, but in MIDI world this can be significant because NOTE ON is actually making a sound and that can make you confused when recording) and then it gets recording. You can confirm this from the MIDI acitivty log.

It doesn't happen with zero latency VSTis like reasynth. Addictive Keys, for example, has 64/128 spls latency(128 here is my audio device's buffer size). Arturia's Piano V2 has also 64/128. This behavior happens with such an instrument. But, even with Addictive Keys, this strange behavior doesn't happen when the starting bar(in the case above it's at 3.1.00) is at 2.1.00. If the starting bar is at 3.1.00 just like the above, this short NOTE ON happens.

I believe this has something to do with how reaper handles the vsti latency when recording.

I want to make it precise so that the previous recording in the time selection isn't played at all. Of course, you can do it by shifting the first note in the second bar to the right slightly, but you know, this is very inconvenient everytime and it's a dirty hack! Another work around is splitting the item and using auto-punch selected items because the issue doesn't happen in this case.

I found a simple work around. It was just so annoying. In that VSTi's fx window, click "2 out" for example. There you click I/O button. Go to PDC (64 spls) > Disable and check it. The sample size may vary depending on your VSTi. It seems to disable PDC for that VSTi and the FX window's left-bottom shows now 0/0 spls. I also don't know what "adjust automation" does, and I also wonder why disable and adjust automation are not exclusively selected but both can be checked.

I am quite sure that there might be some side effects from this(since it's not compensated) but currently I no more hear any note on from the time selection area. Maybe, I could offset the track playback with a negative sample size.

I believe this is some sort of bug.

Last edited by cjunekim; 09-16-2021 at 08:28 PM.
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