Richard Rasker schrieb:
>> I'm trying to help one of my Linux users with a rather frustrating
>> problem: Basically, Cinelerra handles keyframes just fine during
>> preview, but behaves erratically when rendering.....
> OK, I went over & checked things out, and it turns out to be related
> to the track overlay mode (normal/additive/etcetera). The first two
> tracks were set to additive, but the third one (where the problems
> occurred) was set to normal. When trying to create a cross-fade from
> the second to the third track, the fade-out of the second track
> overlaps the fade-in of the third track -- but with the third track
> in "normal" overlay mode, this latter track is only displayed when
> the clip in the second track has completely ended. Setting the third
> track overlay mode to additive as well solved the problem.
Hi Richard,
this sounds familiar! That specific problem has biten me several times.
Basically, something in the handling of Alpha in conjunction with some
colour models got broken with the step to Cinelerra 2.1. (It worked OK
with Cinelerra 2). Basically, when you use additive overlay mode
combined with dissolve transitions, *both* tracks need to be in
additive mode.
I've tried to figure out what goes wrong, but the relevant part of
the engine code is quite large; and because of the multiple colour
models combined with multiple overlay modes (not to mention the
openGL support hacked in all over the place) it is a huge task
even to figure out what's going on and how it "should" be.
My guess at that time was that fixing this bug properly (which
means to *prove* you haven't broken anything else) would require
at least a man month of work; thus I gave up and used the workaround.
> It still seems a bit weird though -- this user has created dozens of
> Cinelerra projects, with literally hundreds of crossfades between
> different tracks, but this is the first time he encountered this
> problem.
Talking from own experience: the problem is tricky and if you don't
know where to look, it may take some time to realise that something
is going wrong here.
Especially: did you know that you can *keyframe* the overlay mode?
Yeah, that's a very powerful and usable feature of Cinelerra,
but if you've turned the "automatic keyframes" on and at the
same time the "show mode keyframes" off, then you might well
accidentally add dozens of overlay mode keyframes all over the
timeline without noticing it.
Hermann Vosseler
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