Create a MKV video containing 2 audio tracks (e.g. using OBS: [1] Desktop Audio, [2] Mic)
Put that video on the timeline
Go to the properties > “Audio” tab and select “Track 2”
Choose “Rebuild Audio Waveform”
Choose “Detach Audio” on the context menu of the timeline object.
Choose “Rebuild Audio Waveform”
Actual Result
After step 3: The timeline is still showing the wave form of Track 1
After step 4: No effect
After step 5: The detached timeline object is showing the wave form of Track 1 (although track 2 is playing)
After step 6: No effect
Expexted Result
*The timeline objects should show the wave form of track 2 of the source video file.
Assumptions
The fact that “Rebuild Audio Waveform” has no effect is evidence that it’s not a refresh problem, but the wave form drawing routine is hard coded to use track 1.
Workaround
I used MkvToolnix to demux the 2nd audio to a separate file and put that on the timeline.
perhaps it is caused by your OBS.
If you use two different channels in OBS and you set it in “mkv”, you will be advised by a warning, that special codecs do not support multiple audiotracks per record.
This is fixed for the next version 19.10.
It will not automatically work on existing projects because I did not want to invalidate everyone’s caches. For existing projects with incorrect waveform on alternate audio track, you need to right-click and choose Rebuild Audio Waveform and save the project for it to relocate the audio level data from cache.
