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Various bugs with fade in/out with the VSE (Sequencer)
Confirmed, NormalPublicBUG

Description

System Information
Operating system: Linux-4.15.0-39-generic-x86_64-with-debian-buster-sid 64 Bits
Graphics card: GeForce GTX 780/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 390.77

Blender Version
Broken: version: 2.82 (sub 6), branch: master, commit date: 2020-01-10 15:30, hash: rB1cb938ef2c92

Short description of error
Fade in/out (opacity) change fails in various ways as described below.

Exact steps for others to reproduce the error

  • Make a new Blender Video Editing project.
  • Add a Color strip and change its duration to 100 frames.
  • Change the colour of the colour strip to make it obvious when it fades in and out.
  • RH-click the strip and select Fade -> Fade In And Out
  • Move the playhead to frame 3. Although the opacity is supposed to be 0.020 (see properties) it is shown in the preview window at full opacity.

  • Changing the blend mode from "Cross" (the default) to "Replace" fixes that. Changing back to "Cross", it stays fixed.
  • The effect seems intermittent. Re-doing the above steps, this time I have full opacity displayed at frame 1:

  • However correct opacity at frame 2:

  • Now if I delete the curve in the graph editor, it seems to sort-of "remember" the opacity, as it fades up and down still, however the opacity shown in the properties window remains at 0.005 for some reason. Despite what the opacity property value is, the opacity now fades up and down at the start, and occasionally flickers from full to no opacity (for example, at frame 44):

  • Interestingly, frame 44 looks like the one frame that wasn't preloaded for some reason (see earlier screenshot) so this may be related.
  • If I try to recover by RH-clicking on the strip and selecting Clear Fade I get this error message:
Traceback (most recent call last):
  File "/home/nick/blender-2.82-1cb938ef2c92-linux-glibc217-x86_64/2.82/scripts/startup/bl_operators/sequencer.py", line 154, in execute
    fcurves = context.scene.animation_data.action.fcurves
AttributeError: 'NoneType' object has no attribute 'fcurves'

location: <unknown location>:-1
  • My guess is that there is some sort of memory caching issue here.
  • The issue isn't related to the Color Strip as such. I originally noticed the effect with a video sequence, however since it can be reproduced with a Color Strip, that is easier to reproduce than supplying a video file.

Thanks for any assistance!

Event Timeline

Campbell Barton (campbellbarton) changed the task status from Needs Triage to Confirmed.Mon, Jan 13, 7:23 AM
Campbell Barton (campbellbarton) changed the subtype of this task from "Report" to "Bug".

Confirmed, thanks for the detailed report.

Tagging @Nathan Lovato (gdquest) on this one though the problems may be lower level than using the API.

I am trying to track down and reproduce further problems I am having with playback of strips. My impression is that it is more of a caching issue than the specifics of the fade-in/fade-out, however as described above that is an easy way of reproducing it. I am not referring here to the proxy files, in the example above I wasn't using them.

Having said that, the Python error message if you try to Clear Fade does indeed seem to be a fade issue.

Not sure if @Nathan Lovato (gdquest) would be able to take this on, in such case I will grab this