VSTi drift as Host Tempo changes

[CMT]

An user was working in a project with some MIDI tracks and Trans Computer Maschine generating pattern stuff. The guy edited the host tempo-track to add some rallentando to the song and after realized that T-C-M shifted figures as accommodated to tempo variations he reported it to us as a bug. We tested the issue and furthermore, we tried with many VST Drum Machines and 303-like instruments to see if other developers did it well. Of course, they don't so we think this is not something we can fix but a limitation of VST. The question is... there's some VST instrument out there that solved this problem? If this is true, we must find a fix too, of course!

Please let us know,

Walter

[RunBeerRun]

I'm not sure exactly what you're asking for-Synthedit help? I think your synth syncs to host tempo and it also goes off tempo when the tempo given to it by the host changes?

[CMT]

Sorry about my ital-nglish, put it this way:

Start a project with a drum MIDI track in a host like Cubase (100% Steinberg VST).
Load either T-C-M, any u-he ltmLab Virtual Machine or Arturia Modular V to generate patterns synced to the host.
Play the project and change tempo while running and voila: VST INSTRUMENTS UPDATE TEMPO ACCORDING TO HOST BUT PATTERN IS NOT ALIGNED (SHIFTED) WITH MIDI DRUM TRACK IN PROJECT!
Of course, If you stop and restart, everything is refreshed and fine, at least with T-C-M but I'm reporting the problem of making tempo changes while the song is going on.

Thanks for showing interest,

Walter

[RunBeerRun]

Hmm, well if other plugins are having the same behavior....

I've never personally shifted a tempo mid-song, and haven't put this to the test. I do use drum machines that sync to host tempo, but with synths or effects I want them NOT to do this, as I make personalized music, I don't want the sound a person can make with minimal effort.

[antto]

try this same test in another DAW, and see if those same VSTs go out of sync or not
i think there isn't much that can be done from the plugin side.. in process() you ask the host for the tempo, and do your calculations that way, assuming the tempo cannot change in the middle of the audio block

[jancivil]

"rallentando" means a ramped tempo track/timeline *gradually* slowing down.
I believe your problem has not to do with 'VST' but with 'beats per minute' and calculating to a grid. IE: I think the ramping for a drum machine {expecting a result that totally makes sense 'in sync' with the midi of the host} is a problematic notion in itself. What does the exported midi file do with the gradual slowing down? How do you determine BPM reliably in that? It's constantly changing!

I remember taking a saved pattern in a Yamaha drum machine and moving the fader to change speed. It was pretty wambly as I recall.

[CMT]

"rallentando" means a ramped tempo track/timeline *gradually* slowing down.
I think the ramping for a drum machine {expecting a result that totally makes sense 'in sync' with the midi of the host} is a problematic notion in itself. How do you determine BPM reliably in that? It's constantly changing!

That's it, and I want to know if some developer worked it out! (seems that nobody in the industry did) I'm going mad thinking if there is a solution...

Thanks for clearing out this important issue so everybody can understand.

[CMT]

Hello everybody,

OK, VST sync seems to be a bit weak but after more sync tests there's good news because we found some plug-ins that passed them all!

Three tests were made:

1 - Changing host project tempo by editing the 'tempo track'
2 - Changing host project 'fixed tempo' manually while playing
3 - Jumping host song position manually while playing

The following plug-ins FAILED tests 2 & 3:

Angry Red Planet Temper
Arturia Modular V
AudioRealism Bass Line 2
AudioRealism Drum Machine
d16 group Drumazon
d16 group Phoscyon

The following plug-ins PASSED all tests:

Arturia Spark
Audio Damage Tattoo
fxpansion Geist
Image Line FruityLoops
Insert Piz Here midiLooper
Oleg Mikheev aka GrayWolf BlueARP
Psychic Modulation Cubix
Sonic Charge MicroTonic 3
sonicbytes phrazor
XT Software energyXT

Opposite to their reliable FruityLoops, the only one that failed all tests was 'Image Line Groove Machine'.

Our 'Trans Computer Maschine' as well as 'u-he ltmLab Vintage Drum Machine Series' failed only test 2 but we are already working out a solution because we want to have the best sync possible before launching our next pattern-based product.


Regards from The CMT Team!

[antto]

would you tell us what your solution is?

[CMT]

would you tell us what your solution is?

Because an only clock can't do the job accurately, we are thinking about a second one...