frames being repeated or dropped

[hn-88]

When encoding a single video input to output, found duration had reduced from 24 minutes to 22, and also some jerkiness in motion. When tried to reproduce by creating a video of frames with ffmpeg, found ffmpeg was also duplicating frames?!
https://gist.github.com/hn-88/95dbd59767dcdff23eab2f2be5880c2f

[hn-88]

Possibly this is due to using ffmpeg in the backend, and this issue?
https://superuser.com/questions/1255380/ffmpeg-duplicating-frames

[hn-88]

OCVWarp works without frame repeats, OCVvid2fulldome doesn't, for the same input video.
The difference between OCVWarp and OCVvid2fulldome seems to be that in OCVWarp,

outputVideo.open(NAME, ex, inputVideo.get(CAP_PROP_FPS), Sout, true);

while in OCVvid2fulldome, it is

outputVideo.open(NAME, outputVideo.fourcc(outputfourcc[0], outputfourcc[1], outputfourcc[2], outputfourcc[3]), 
       outputfps, Sout, true);

[hn-88]

As seen with the comments for
https://gist.github.com/hn-88/95dbd59767dcdff23eab2f2be5880c2f
ffmpeg assumes 25fps input as default, and adds duplicate frames if output is 30 fps.

Maybe we can try setting input fps = desired output fps.

[hn-88]

e45311a does not seem to help. So, the only workaround seems to be to ensure all input videos have the same fps as the output fps?

[hn-88]

Found the bug (or at least one bug) - it is not a problem with opencv's fps handling, but instead my handling of the outputfps double from ini file - no strtod() used!