xLights Scheduler starts MIDI output before beginning a step


New elf
Aug 29, 2021
The xLights Scheduler application starts a MIDI output stream before the step actually starts playing when the "Play Selected" button is pressed. This causes any other application using the MIDI stream to begin its media play before xLights Scheduler's steps actually begin playing. The consequence of this is that there's about 0.5 to 1 second of lag between the two media files playing.
Additionally, the MIDI stream is not entirely smooth. It has a couple of jerks here and there over its course.

To Reproduce

  1. Start xLights Scheduler
  2. Configure an output MIDI stream for a step
  3. Configure the step to also play some media file (video/audio)
  4. In a separate application (we've tried nearly a dozen different applications), use the MIDI source as an input stream
  5. Go to xLights Scheduler and hit the "Play Selected" button to play the steps
  6. Observe that the external application starts playing its media immediately, but xLights Scheduler takes almost half a second more to play its own media causing a de-sync of about 0.5-1 seconds
Expected behavior
When the step is played, both media players/outputs should happen at the same time. In fact, the external player starts playing earlier as the MIDI stream has already started, but the xLights Scheduler step is not even highlighted green until that point. See the attached screenshots and video for more clarification.


Versions (please complete the following information):

  • OS: Windows 10
  • xLights version 2021.02


Getting there slowly..
Dec 12, 2016
Central Coast
Hi Tammy, best to post xlights issues on the xlights github at