[FFmpeg-trac] #9455(undetermined:closed): Overlay n expression being off 1 frame

FFmpeg trac at avcodec.org
Fri Oct 15 15:57:50 EEST 2021

#9455: Overlay n expression being off 1 frame
             Reporter:  Jozef        |                    Owner:  (none)
  Chutka                             |
                 Type:  defect       |                   Status:  closed
             Priority:  normal       |                Component:
                                     |  undetermined
              Version:  4.3.2        |               Resolution:  wontfix
             Keywords:  overlay n    |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
Comment (by Jozef Chutka):

 Thanks for your quick reactins Elon.

 I was under impression that the frame numbering in my whole example should
 be equal/synced for all used sources. When printing `n` with drawtext it
 renders the same value for any source used.

 Do I get it right that `n` in overlay starts at 1 while in all other
 filters starts with `n` being 0? And so, for `scale=w=n` (`n` is i.e. 0)
 while following `overlay=x=n` filter has different `n` - being 1 already.

 Can you please point me to the documentation that would explain it in more
Ticket URL: <https://trac.ffmpeg.org/ticket/9455#comment:3>
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