Am 01.11.2010 01:27, schrieb Ivan Volosyuk:
> According to manuals Cinelerra keyframes are actually between frames, but
> how far is the keyframe from previous and next keyframe in time?

<rant>
I know that nice formulation found in the manual...
I've seen already a lot of users getting confused by that behaviour.

Actually it seems that the behaviour was rather defined from the
implementor's perspective, not the user's perspective -- Why would
any editor want keyframes "lag" behind for 1 frame?? Still the more
when they also "lag" behind when playing backwards, which makes
precise positioning of keyframes into a sort of an intelligence test
</rant>

> I have very specific need: I have one scene which is zoomed in
> significantly. Next scene should use default projection (no zoom).

Yeah, well known problem, got bitten by that numerous times

* probably the simplest solution is to use a separate track and
  leave the zoom constant there. This is still the more true, because
  the design of transitions are similarily half-baked, i.e. you can't
  just dissolve between two adjacent scenes when the zoom is changed.

> It seems in cinelerra that means that I should have zoomed in projection
> parameters [0,0, 3] after the last frame in first scene. I also need default
> projection [0,0, 1]  before the first frame of second scene. It seems they
> refer to the same parameters set. Does the keyframe is located immediately
> before the next frame and frame-time away from previous frame?

* Otherwise, if you're bound to do it on this single track (and
there might be some other reasons which do force you sometimes to do
it this way), then we'd need to have a close look at the implementation
logic. First of all, beacuse we're intending to render the final result,
the behaviour for playing forward is relevant. Dot't get confused when
Cinelerra seems to show wrong settings either when the still frame
at the cut position is displaced, or when single-stepping backwards.

Generally speaking, Cinelerra displays each frame when the cursor
has passed *over* this frame, i.e. you get the result of calculating
the frame in the output when the cursor has moved to the right side
of the frame. But the corresponding keyframe has to sit on the left
side of the same frame, in order to be still relevant. That is,
because keyframes are always effective starting from their position
onwards.

prevScene    newScene
_____:_____|_____:_____:
.....K1....K2...........

           ^cut

K1 gets the settings [0,0, 3]
K2 gets the settings [0,0, 1]

(her I assumed that "prevScene" is zoomed in; of course we get a
similar situation at the begin of that zoomed scene)

hope that helps
Cheers
Hermann V.

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