Crossfade bug? Previous Image does not fade out

OS: Windows 10 Home Version 10.0.19045
Shotcut: 24.02.29

Steps to reproduce:

  • Create new project
  • Import two images with different width/height ratio (e.g. one portrait, one landscape)
  • Add new video track
  • Drag the images to the video track
  • Create a crossfade between the images by dragging one over the other

Observation (see screenshots):

  • Image#2 (red portrait) fades in → OK.
  • Image#1 (blue landscape ) does not fade out during the cross fade! → expected that it does fade out

Screenshots (from top to bottom)

  • At begin of crossfade:
  • In the middle of crossfade:
  • At the end of crossfade (Blue Image 1 still fully visible!)

Thanks for your support!

You need to have a color on V1.

1 Like

This happens because Shotcut does not blend the bottom video track with anything, and a crossfade transition adjusts the alpha channel (opacity) of each input while blending them. Thus, image 2 has image 1 as a background, but image 1 does not have anything.

Image#1… expected that it does fade out

Fade out to what, black or blue?

To understand better, place an image or video on V1 by itself, add the Opacity filter and reduce it. Nothing happens, because V1 is not blended with a hidden black background. Having to always blend a track when most people do not need it requires a fair amount of CPU, and Shotcut needs to reduce overhead because it is not exactly fast.

The workaround is to make a background track with a color clip (or anything else, could be another image or video).

Thanks for your help, with that (easy) workaround I now get the desired result.

(Note: I had updated to 24.02.29 just recently. Before had I used a quite older version (2-3yrs?), and there the behavior was different, and no black background track was required.)

Thanks again!

Old versions did not properly respect the alpha channel of the sources. For example, it would not correctly crossfade text clips (atop some background on lower track).