[CinCV TNG] lazy insertion point movement when using keypad

Frederic Roenitz ml1 at aimvis.de
Sun Aug 27 13:18:57 CEST 2017


Hi GG/Phyllis,

 > I have added a possible addition of a "preference" for the "play
 > forwards/positioning" controversy for future program coding into our
 > personal debugle.org cinelerra issues database.

:)


 > we both obviously like it the way it is.
 >
 > GG/Phyllis

It wasn't that obvious to me. Next time please just emphasize this at
the beginning. :)



In the meantime I need to learn how to efficiently work with
"ov"-scenarios.


Please have a look at the following use case scenario and tell me what
I am doing wrong or how you would do it:


use case
========

I am looking at the compositor.
I am using the keypad keys.
After a seek operation, the Insertion point cursor is at timeline position 0.

The video clip in the timeline shows for example a traffic light that
changes from red to green (regardless if traffic lights do this in
reality).


I want to cut before the image changes (traffic light changes from red to green).
The image change occures at timeline position 3.

The cutting should result in:
Fame 2 should be the last one frame to see in the clip.


step 0 (start)
--------------

red traffic light

  vo
  0 1 2 3 4 5
  |_|_|_|_|_|
   0 1 2 3 4


step 1
------

keypad1

   ov
  0 1 2 3 4 5
  |_|_|_|_|_|
   0 1 2 3 4

image didn't change.


step 2
------

keypad1

     ov
  0 1 2 3 4 5
  |_|_|_|_|_|
   0 1 2 3 4

image didn't change.


step 3
------

keypad1

       ov
  0 1 2 3 4 5
  |_|_|_|_|_|
   0 1 2 3 4

image didn't change.


step 4
------

keypad1

         ov
  0 1 2 3 4 5
  |_|_|_|_|_|
   0 1 2 3 4

now I see the change (green traffic light)


step 5
------

keypad4

        vo
  0 1 2 3 4 5
  |_|_|_|_|_|
   0 1 2 3 4


step 6
------

cut.

        v
  0 1 2 3
  |_|_|_|
   0 1 2



my thoughts:

  Step 4 and step 5 would not be necessary with playhead policy:
  "always 'vo'".

  Currently we always have to do two more steps than for example in CVE.
  (Thanks for the hint, Igor!)


  In which case(es) does the currently used playhead policiy for playing
  forward come in handy?

  I really don't konw when.


So:

How would you do this?

What is the most efficient way to do this?


Thank you and kind greetings

Frederic


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