Timebase drift in Soundfont and VST playback

Issue type

General playback bug

Description with steps to reproduce

1. Create a score that plays for an extended time. The attached sample score lasts for 1 hour and consists of repeated snare drum hits on the beat. (See attached score.)
2. Set playback using various rendering engines and export the piece. For the example shown below, stems were generated using Soundfont (both MS Basic and Live HQ Natural), MuseSounds (using Big Kit), and VST (using SSDSampler 5) renderings.
3. Import the resulting sound files into a DAW (such as Reaper). Set the tempo in Reaper to the tempo of the piece (in the example here, 60 bpm), providing an accurate reference for the start of each beat.
4. Examine the first or second beat of the piece. Note the starting positions of the waveforms relative to the beat. (See attached screenshot.)
5. Examine the last beat of the piece. Note that while the starting position of the MuseSounds waveform is the same as it was at the beginning of the piece, the positions of the Soundfont and VST waveforms have shifted. In the example shown, the drift corresponds to approx 36 ms over 1 hour. (See attached screenshot.)
6. Expected behavior is for the start time of the waveform to be constant regardless of the length of the piece. Since by default MuseScore studio uses MS Basic to render the metronome beat, this creates the false impression that MuseSounds is drifting away from the beat over very extended times. It appears that MuseSounds is in fact keeping time correctly, but the metronome (as rendered using MS Basic) is what is actually drifting.

Supporting files, videos and screenshots

Sample 1 hour score: 1 Hour of Snare Drum.zip

Screenshot showing waveforms in Reaper of second beat of 1 hour score:

Screenshot showing waveforms in Reaper of last beat of 1 hour score:

In which versions of MuseScore Studio is this issue present?

I have confirmed this issue in 4.7.4 as well as 4.2.0. I have not checked all versions between them, or prior to 4.2.0.

Regression

No.

Operating system

Windows 11

Additional context

The drift does not appear to be constant across MuseScore Studio versions. As noted above, in 4.7.4 the drift was approx 36 ms over 1 hour. But in 4.2.0, the drift is closer to 300 ms over 1 hour.

Checklist

• This report follows the guidelines for reporting bugs and issues
• I have verified that this issue has not been logged before, by searching the issue tracker for similar issues
• I have attached all requested files and information to this report
• I have attempted to identify the root problem as concisely as possible, and have used minimal reproducible examples where possible