[FFmpeg-trac] #8460(undetermined:new): H.264 VFR timestamp hazards (which means frame duration... or playback experience hazards)

[FFmpeg]

#8460: H.264 VFR timestamp hazards (which means frame duration... or playback
experience hazards)
-------------------------------------+-------------------------------------
             Reporter:  gdgsdg123    |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:  git-
  undetermined                       |  master
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 [http://trac.ffmpeg.org/ticket/8063#comment:2 123.avi]
 [[BR]]
 [[BR]]
 {{{
 ffmpeg -y -i "123.avi" -c:v h264_nvenc -r 1 -g 1 -vsync vfr "temp.avi"
 }}}
 The timestamp of the 1st frame is delayed according to `-r` (by 1/r
 exactly), while the rest of the timestamps remain unchanged (have verified
 this with more complex input source).

 Which negatively affects the 1st frame's duration. (and the impact
 persists in further re-encodings)
 [[BR]]
 {{{
 ffmpeg -y -i "123.avi" -c:v h264_nvenc -r 1 -g 2 -vsync vfr "temp.avi"
 }}}
 The duration of the 2nd frame is influenced by `-r`.
 [[BR]]
 {{{
 ffmpeg -y -i "123.avi" -c:v h264_nvenc -r 1 -g 3 -vsync vfr "temp.avi"
 }}}
 Appeared normal. (all timestamps are delayed accordingly)
 [[BR]]
 [[BR]]
 [[BR]]
 {{{
 ffmpeg -y -i "123.avi" -c:v libx264 -r 1 -g 1 -vsync vfr "temp.avi"
 }}}
 Normal.
 [[BR]]
 {{{
 ffmpeg -y -i "123.avi" -c:v libx264 -r 1 -g 2 -vsync vfr "temp.avi"
 }}}
 The duration of P-frames (the 2nd frame in this case) become 1/r. (absent
 timestamp information in the packet?..)
 [[BR]]
 {{{
 ffmpeg -y -i "123.avi" -c:v libx264 -r 10 -g 3 -vsync vfr "temp.avi"
 }}}
 Better demonstration of the above problem.
 [[BR]]
 {{{
 ffmpeg -y -i "123.avi" -c:v libx264 -r 10 -qp 0 -g 3 -vsync vfr "temp.avi"
 }}}
 Normal. (no P-frame in the output, due to the scenecut decision of x264)
 [[BR]]
 ----

 Unsure if it's the encoder's fault or FFmpeg's.
 [[BR]]
 [[BR]]
 [[BR]]
 **Off-Topic**
 [[BR]]
 {{{
 ffprobe -hide_banner -show_entries "frame" -select_streams v:0 -of "xml"
 "temp.avi"
 }}}
 {{{
 ffprobe -hide_banner -show_entries "frame=best_effort_timestamp_time"
 -select_streams v:0 -of "compact=nk=1:p=0" "temp.avi"
 }}}
 ...In case you don't know how to use FFprobe.
 [[BR]]
 [[BR]]
 And in the world of CFR... the duration doesn't have to really exist.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/8460>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker