[CinCV TNG] lazy insertion point movement when using keypad

Phyllis Smith phylsmith2017 at gmail.com
Fri Aug 25 01:28:54 CEST 2017


On Thu, Aug 24, 2017 at 2:14 AM, igor_ubuntu <sitelve at gmail.com> wrote:

>
> Could you please explain this behavior  https://files.fm/u/zfbzac79 ?
> This new screencast shows same file with 1fps. The file has 10 images: img1
> img2 ... img10
>
> I place (manually) the insert. point(cursor) between* img4* and *img5*
> -> Compositor shows the next img5 (the next one in relation to the cursor)
> *(because I make  'seeking')*
> I press the bt. 'Frame forward' -> Compositor shows the previous *img5* (the
> previous one in relation to the cursor) that has just been played (*because
> I make   'playing')*
> I press the bt. 'Frame backward' -> Compositor shows the * img5*  *Why ?*
>
> Simplest explanation by Phyllis - when you *"play forwards", the frame to
the right of the cursor* *gets displayed.*  When you "*play backwards", the
frame to the left of the cursor gets displayed*.  It is just that simple.
- - - - - - - - - - - - - - - - - - -
*Technical explanation by GG from the code:*

1) open Example10.mov, 10 frames
2) press f to "fit" the timeline
3) make sure settings->align_cursor_on_frames is set
now...
4) seek to frame 4 by clicking timeline at position 4, compositor shows 5,
since the media counts from 1 and the timeline counts from 0.  This is
correct.
5) press KP1 to play next frame.  According to playback strategy:

*  When play is forwards, the next unit is displayed,    and the position
is advanced one unit.*
  So the next frame is 4, (shows 5) it is displayed.
   The position is advanced from 4 to 5.  This is correct.
6) press KP4 to play the prev frame.  According to playback strategy:

*  When play is in reverse, the previous unit is displayed,   and the
position is reduced one unit.*
 So the prev frame is 4, (shows 5) it is displayed.
 The position is reduced from 5 to 4.  This is correct.

Watch the zoombar (bottom of main window) position.  It shows the current
position is just before the next frame to be displayed when going forwards,
and just after the frame to be displayed when going backward... except just
after a
seek.  Technically, since seeking just resets the position. It would be
correct not to update the compositor, but most would agree, it is nice to
seek and show the next frame to confirm that it is the frame you expected
to see.

-------------
>
> The second part of the screencast shows
> - I am placing the cursor between frames manually in the direction  from
> 10 to 1  (seeking)
> - I am pressing  the bt. 'Frame backward'   I'm moving in the direction  from
> 10 to 1  (playing)
>
> But there is no difference between seeking and playing
> *Why?*
>
>
There is a difference.  There is no direction when seeking.
According to the strategy:
The position is set to the seek target, and the next frame is displayed.
In the case you describe, the reverse play and seek sequence show
the same frames, but you could see any sequence when using only seek.

You may think there is a more "intuitive" way to do this, but the
strategy rules are "context free".  This means it will always do the same
thing, no matter when or where the rule is used.  It makes it obvious
what the program should be doing in every case.


GG/Phyllis
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.cinelerra-cv.org/pipermail/cinelerra/attachments/20170824/db12a150/attachment.html>


More information about the Cinelerra mailing list