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IDProjectCategoryView StatusLast Update
0008769ardourbugspublic2021-07-05 16:28
ReportermrMute Assigned To 
Status newResolutionopen 
PlatformDebian GNUOSLinuxOS Version(any)
Product Version6.8 
Summary0008769: MIDI notes drop out when vst automation points are snapped to the same start point.
DescriptionThis happens when using VST3 synths:

When MIDI notes and processor automation are snapped to the same grid lines notes can drop out.

I tested this with U-he Diva and Tal-software synths.

When i try the VST2 versions of the plugin's the notes play as they should.
Steps To ReproduceCreate a MIDI region.

Add a VST3 instrument.

Draw notes.

Draw processor automation and snap the point to the same grid lines.

(see attached screenshot)
TagsMidi, VST3



2021-07-03 20:00


automation.png (25,966 bytes)   
automation.png (25,966 bytes)   


2021-07-04 22:03

administrator   ~0026027

I just tested that with Diva (1.4.3), automating the "output" volume, and cannot reproduce the issue.

Could you share the .ardour session file? perhaps there is something else that is key here, maybe related to BPM/samplerate (rounding issues)?


2021-07-05 15:09

reporter   ~0026028

Thanks for looking into this.

I didn't keep the previous test session, i was using the new vst3 version of TAL Noisemaker in that one.

I created a new one using Diva and automation for the output parameter. i get stuck notes this time.

I attached an archive of the test session.


2021-07-05 15:19

reporter   ~0026029

Here is a test session using the vst3 version of TAL Noisemaker:

In this case notes are dropped. The same thing happens for the other TAL plugins.


2021-07-05 16:28

administrator   ~0026030

I've mitigated the issue in Ardour 6.8-68-g13f5fb3dee, but the underlying issue cannot be fixed before Ardour 7.0
There are rounding errors when converting music-time (bar/beat) to sample-time which leads to stuck notes, among other issues.

In this case the rounding error coincided with splitting the process cycle to send automation-data to VST3 plugin (process n samples, update parameter, process remaining samples).
VST2 plugins were not affected since VST2-instruments are always called with a fixed buffer-size.

PS. using a sample-rate of 48000 instead of 44100 greatly reduces the likelihood of those rounding errors. which is why I was not able to reproduce this issue.

Issue History

Date Modified Username Field Change
2021-07-03 20:00 mrMute New Issue
2021-07-03 20:00 mrMute Tag Attached: Midi
2021-07-03 20:00 mrMute Tag Attached: VST3
2021-07-03 20:00 mrMute File Added: automation.png
2021-07-04 22:03 x42 Note Added: 0026027
2021-07-05 15:09 mrMute File Added: automation_test_2021-07-05_170220.ardour-session-archive
2021-07-05 15:09 mrMute Note Added: 0026028
2021-07-05 15:19 mrMute File Added: automation-test-tal_2021-07-05_171503.ardour-session-archive
2021-07-05 15:19 mrMute Note Added: 0026029
2021-07-05 16:28 x42 Note Added: 0026030