Last frame in ProRes video has incorrect duration

[FrugalCourtland]

Summary of the bug:
When encoding a number of frames that are not a multiple of the framerate with prores, the last frame has an incorrect duration. If the number of frames is a multiple of the framerate (i.e. the video duration is a whole number of seconds), this does not appear to occur. Other codecs, such as mp4, do not appear to have this issue.

How to reproduce:

% ffmpeg -framerate 30 -i %02d.png -codec:v prores prores.mov
% ffprobe -show_frames prores.mov

[FRAME]
media_type=video
...
pkt_pts=1536
pkt_pts_time=0.100000
pkt_dts=1536
pkt_dts_time=0.100000
best_effort_timestamp=1536
best_effort_timestamp_time=0.100000
pkt_duration=522
pkt_duration_time=0.033984
...

Note that the duration and duration_time for the last frame are different from the rest of the frames. This can cause an issue for codecs that use this value, see #7025.

ffmpeg version 3.4.1 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 7.2.0 (GCC)
ffprobe version 3.4.1 Copyright (c) 2007-2017 the FFmpeg developers
  built with gcc 7.2.0 (GCC)

[FrugalCourtland]

Input frames (4 PNGs)

[FrugalCourtland]

ProRes video with incorrect framerate (created with ffmpeg command shown above)

[Carl Eugen Hoyos]

Is this issue reproducible with current FFmpeg git head?

[FrugalCourtland]

Replying to cehoyos:

Is this issue reproducible with current FFmpeg git head?

I'm not setup to build from git, but I was able to repro it using the latest snapshot (ffmpeg-20180215-8a8d0b3-win64-static).

ffprobe version N-90065-g8a8d0b319a Copyright (c) 2007-2018 the FFmpeg developers
  built with gcc 7.2.0 (GCC)
ffmpeg version N-90065-g8a8d0b319a Copyright (c) 2000-2018 the FFmpeg developers
  built with gcc 7.2.0 (GCC)

[Elon Musk]

Can not reproduce.