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Waveforms in vse vanish when a strip has a volume fcurve with no animation points.
Open, Confirmed, HighPublic

Description

Blender Version
Broken: 2.80, 2.81

Short description of error
When an fcurve is created on a vse strip in python, but no points are added to the curve, the waveform vanishes (as if it is at volume 0), and it will not display again until the fcurve is removed, or a point is added.
Note: the audio will still play back fine, so this seems to be exclusively limited to waveform display.

Exact steps for others to reproduce the error

  1. Enable waveform display (View menu > Waveform Displaying > Waveforms On)
  2. Load 2 audio files into a fresh vse
  3. Add an animation point to audio file 1 (to ensure the scene has animation data)
  4. Select only audio file 2
  5. Paste the following into a console:
bpy.context.scene.animation_data.action.fcurves.new(data_path=bpy.context.scene.sequence_editor.active_strip.path_from_id('volume'))
  1. Move the cursor to cause a refresh.

Details

Event Timeline

This same thing happens when adjusting the Hold Cut start/end frames in strip's Time properties.

Reproduce:

  1. Select Audio Strip
  2. Check Display Waveform (Properties Panel > Adjust > Sound > Display Waveform)
  3. Adjust Start/End frames of the Hold Cut (Properties Panel > Time > Hold Offset Start/End
  • Usually only happens when adjusting the End frame for me
  • The first couple adjustments don't reproduce the error. Must adjust several times.

Workaround:

In order to refresh the audio to see the waveforms again, follow these steps:

  1. Save your file
  2. Go to File > Open Recent > The file you just saved
Richard Antalik (ISS) triaged this task as Confirmed, High priority.

@Justin (Blender_Frenzy) This is completely different bug.

There is waveform redraw forced somewhere deep in depsgraph probably.
Can not make fix right away unfortunately.

@Justin (Blender_Frenzy) I will post this bug so I won't forget