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Maniphest T58011

Deleting the strip leading up to a crossfade
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Description

System Information:
Windows 8

Blender Version:
Broken: 2.79b & 2.80

Short description:
When deleting a stip leading up to a crossfade, the transition will move the transition on top of the following stip and in the full duration of that strip.

Exact steps for others to reproduce the error:

  1. Add two movie strips to the sequencer in the same channel with a bit of space between them.
  2. Select both strips.
  3. Shift + A > Transition > Cross
  4. A transition should now have been created between the two strips.
  5. Delete the left strip.
  6. The transition will now place itself in the same channel op top of the strip to the right and with the same duration.
  7. Moving the two strips makes them move into separate channels.

The process is illustrated in this gif:
https://devtalk.blender.org/uploads/default/original/2X/9/95ec526e9cc369caae9b55be1c46c03f71035f38.gif

Theory:
Maybe it is because of the frame_start of the cross transition strip is read-only? So instead of having its own frame_start value defined it inherits the frame_start value of the second strip? This bug may affect all effect and transition strips(without frame_start)?

Details

Type
Bug

Event Timeline

Brecht Van Lommel (brecht) added a subscriber: Brecht Van Lommel (brecht).Nov 23 2018, 3:38 PM
Brecht Van Lommel (brecht) triaged this task as Needs Information from User priority.

Please provide all the information requested in the bug submission form:
https://developer.blender.org/maniphest/task/edit/form/1/

Particularly a .blend file and exact steps to redo the problem.

Peter Fog (tintwotin) updated the task description. (Show Details)Nov 23 2018, 6:25 PM
Peter Fog (tintwotin) raised the priority of this task from Needs Information from User to Needs Triage by Developer.
Philipp Oeser (lichtwerk) added a subscriber: Philipp Oeser (lichtwerk).Nov 26 2018, 10:39 AM
Philipp Oeser (lichtwerk) claimed this task.
Philipp Oeser (lichtwerk) triaged this task as Normal priority.

Transitions/Effect Strips are usually based on the overlap of two strips (technically defining their start/end by the largest start and smallest end of the two strips).
If one of the inputs is deleted, blender will just treat it the same as the remaining one.
This is by design and no bug afaics.

Your usecase is already a little bit 'out of the usual' because the strips dont overlap (but instead are on the same channel and have "a bit of space between them").
Not sure how useful this really is? (You would have to describe in more detail why you need a setup like this)

That being said, that leaves us with the remaining issue (the cross not being automatically moved up above the remaining strip -- that can be looked at...)

Nathan Lovato (gdquest) added a subscriber: Nathan Lovato (gdquest).Nov 26 2018, 11:08 PM

Your usecase is already a little bit 'out of the usual' because the strips dont overlap (but instead are on the same channel and have "a bit of space between them").
Not sure how useful this really is? (You would have to describe in more detail why you need a setup like this)

That's the closest to how it works in other video editing programs. It keeps the editing board a lot cleaner: when you fade from one clip to the next, having them in the same channel tells you there's continuity between the two. And these fades are already supported, even if that was not intended.
Having the fade effect inline with the other strips also makes it possible to select the handles on either sides of a crossfade with Ctrl Alt Select Mouse, allows you to select these linked strips with L, to use Ctrl L to select a block of strips, etc.