Clicks when playback is stopped or paused

[michaelgregorius]

Bug Summary

Playing a track and pressing pause or stop can lead to audible clicks. This is likely caused by an immediate stop of the audio output.

Steps to reproduce

1. Add a TripleOscillator to the song editor.
2. Activate the volume envelope of the TripleOscillator in such a way that it does not produce any clicks. Example:
   • Hold: 0
   • Decay: 0,5
   • Sustain: 1
   • Release: 0,1
   • Amount: 1
3. Add a clip with a long and low note, e.g. A3, to the track with the TripleOsciallator.
4. Start playback and press pause or stop. Repeat several times if needed.

Expected behavior

The sound fades out quickly but without a click.

Please refer to the first half of this comment for the results of some experiments on how REAPER handles these events. I don't want to repeat all of this here. The gist of it is that pause stops the sound immediately and without clicks whereas stop lets instruments and effects ring out.

Stop seems to send a note-off event to all instruments but keeps processing the audio coming from the tracks.

Pause seems to retain as much state as possible and then continues from that state if playing is resumed. The fact that this does not create any clicks seems to indicate that REAPER does not immediately stop when the pause event is received but that it at least keeps processing to fill a buffer that's long enough so that a quick fade-out can be applied.

Actual behavior

A click is heard. Because we have ensured that the instrument is not the source of the clicks this is likely caused by the implementation of the pause and stop events.

Affected LMMS versions

Master. At the time of writing at commit f0aa286.