[FFmpeg-trac] #7662(avfilter:new): When using video filter fps, provide an option to retain actual pts, and pts_time for frames

[FFmpeg]

#7662: When using video filter fps, provide an option to retain actual pts, and
pts_time for frames
-----------------------------------+--------------------------------------
             Reporter:  vishal733  |                     Type:  defect
               Status:  new        |                 Priority:  normal
            Component:  avfilter   |                  Version:  git-master
             Keywords:  fps        |               Blocked By:
             Blocking:             |  Reproduced by developer:  1
Analyzed by developer:  1          |
-----------------------------------+--------------------------------------
 Summary of the bug:
 How to reproduce:
 {{{
 % ffmpeg -i input -filter_complex "showinfo,fps=20,showinfo" out_%03d.png
 ffmpeg version: master (current head:
 ed3b64402ef770097f81e4f1e17f1fca253159aa, avfilter/af_anlmdn: ignore too
 small values
 )
 built on macOS
 }}}

 Output:
 {{{
 [Parsed_showinfo_0 @ 0x...] n:   0 pts:      0 pts_time:0       pos:
 93846 ...
 [Parsed_showinfo_0 @ 0x...] n:   1 pts:   3000 pts_time:0.0333333 pos:
 95321 ...
 [Parsed_showinfo_2 @ 0x...] n:   0 pts:      0 pts_time:0       pos:
 93846 ...
 [Parsed_showinfo_0 @ 0x...] n:   2 pts:   6000 pts_time:0.0666667 pos:
 95358 ...
 [Parsed_showinfo_0 @ 0x...] n:   3 pts:   9000 pts_time:0.1     pos:
 95398 ...
 [Parsed_showinfo_2 @ 0x...] n:   1 pts:      1 pts_time:0.05    pos:
 95358 ...
 }}}

 In the output, showinfo_0 refers to timestamps before action of fps. and
 showinfo_2 refers to timestamps after action of fps.
 Clearly you can see that pts is artificially alterered for frames obtained
 after fps filter. (Ex: pts of frame at pos 95358 is altered from 0.0666667
 to 0.05)
 Can we not have a pts_bypass mode which allows to have the pts of frames
 unaltered.
 This will be really useful for applications using ffmpeg to decode frames,
 and then having accurate back-correspondence.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/7662>
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