I still don't really understand why the otherwise so full-featured kdenlive does not allow to reverse a clip (play it backwards), especially because MLT includes such a feature.
Maybe the reason is, that combining reverse with the speed effect does not seem to work.
As a workaround for the missing reverse effect, I am creating a .mlt file with something like this:
melt framebuffer:original.mov?-1 -consumer xml:reversed.mlt
The '?-1' reverses the video and the resulting .mlt file can be used in a kdenlive project just fine.
However, applying the speed effect in the project to such a clip does not seem to work; the clip plays (also after rendering) at the same speed.
So I tried to apply both reverse and speed (i.e. 500%) in the same command:
melt framebuffer:original.mov?-5 -consumer xml:reversed.mlt
This *seems* to work but when adding the resulting .mlt file to a project, the clip is somewhat messed up - it plays reverse at the changed speed, but only a part of it, so it is unusable.
Question: Is this a kdenlive or MLT issue? Is this the reason why a reverse effect is not available in kdenlive?