8000 jack-transport: possibly uninitialized `position->beats_per_minute` in `update_bpm`. · Issue #7 · zynthian/jack-smf-utils · GitHub
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jack-transport: possibly uninitialized position->beats_per_minute in update_bpm. #7

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asrcpq opened this issue May 11, 2025 · 0 comments
Open

jack-transport: possibly uninitialized position->beats_per_minute in update_bpm. #7

asrcpq opened this issue May 11, 2025 · 0 comments

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@asrcpq
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asrcpq commented May 11, 2025 •
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Problem

Using jack-smf-player under jack-transport mode (i.e., without -t flag) causes all events in the MIDI file to be sent immediately regardless of freewheel setting.

Environment

  • OS: Alpine Linux v3.21
  • JACK server: JACK2 (jackdmp)
  • Version: master

Investigation

My understanding is that timebase callback is currently disabled in jack-smf-player.c#L576 which was supposed to provide the BBT information based on the documentation.

Therefore, the update_bpm function might be called with BBT field uninitialized. In my environment, the uninitialized value is often a tiny double, which passed the zero check and assigned to position->beats_per_minute and further used for time calculation jack-smf-player.c#L346, leading to the incorrect playback speed.

Solution

A quick solution is to check the BBT bitmask against position->valid and skip the BPM update if the information is not included, see this commit.
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