Track silent after parameter-triggered transition with transition timeline - regression between 2.02.25 and 2.02.34

[JayOrbaum]

We have a 2D timeline event (a musical theatre song) where a parameter-triggered transition with a transition timeline leaves one track silent after the transition completes - on 2.02.34, but not on 2.02.25.

Setup

• A quantized transition region (4-bar quantization) spans a loop region. Its destination marker sits about 6 bars past the loop’s end, and the rule carries a 2-bar transition timeline with a destination region (a vocal enters over the fade; the backing track’s next instrument starts exactly at destination + transition timeline length).

• • The transition is triggered by setting its global parameter mid-loop via Studio::System::setParameterByName. Reproduces with and without ignoreseekspeed.
    Observed on 2.02.34 (FMOD for Unity - reproduced both through the editor auditioning system and on a bare event instance, no other code involved):

• When the transition timeline completes, two voices briefly exist on the affected track: the source-side voice (faded to zero by the transition’s fade-out curve) and the destination-side voice (correct and audible).

• • The engine then stops the destination-side voice and keeps the zero-gain source-side voice, which continues advancing through the file with Channel::getAudibility() == 0.000. The track stays silent from the arrival until its next instrument trigger - in our event, the rest of the song.
• • Per-voice traces (positions, current sounds, audibility per channel) are available on request.
    On 2.02.25, same banks and same steps: the destination-side voice survives and the track plays correctly. FMOD Studio 2.02.25’s own transport also plays the event correctly.

We suspect the 2.02.30 change “Fixed transition timeline source region fade curves failing to make instruments go completely silent” - it is the only transition-timeline change between the two versions and matches the symptom’s direction (the fade-out’s silence appears to stick past the transition’s end). We don’t see a related fix in the 2.02.35 notes.

Happy to provide the project and banks privately if useful.

[Connor_FMOD]

Thank you for bringing this to our attention and the detailed post. Your project can packaged:

and uploaded to your profile. Could I please grab the name of the event in question as well?