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Hi,

I'm trying to programmatically cut videos before using them in Kinovea. That is, I have a Excel/csv file with video filenames and start/stop frames manually established through Kinovea. I want to cut to EXACTLY these frames.

So far ffmpeg (ffmpeg.org) seems to be my best shot. Seems like Kinovea is using it as a building block, too.

My issue is:

1) If I happen to cut to a position which is not a keyframe (aka i-frame), Kinovea can not load the video anymore (screen appears black, yet e.g. VLC can still play it).

2) If I convert the video in ffmpeg to turn all frames into keyframes, the quality drops (in/output is MP4 and I'm not recording). I'm not sure why this is, but I'm new to video editing/encoding. I would have thought, that only file size and playback performance would worsen. I understand, that this is not an ffmpeg forum, but since Kinovea uses it internally, maybe the developers have some insight here?

3) Perhaps I could resolve the quality issue by exporting in ffmpeg to a lossless format. But I have no idea which can be read by Kinovea. I don't think any of those listed in the FAQ (kinovea.org/help/en/002.html) are lossless, correct?

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commands used in ffmpeg

1) Cut video unCut.MP4 from 18.44s to 20.44s (video is 100 Hz and times where manually picked in Kinovea (toe off in my case)
> ffmpeg -i unCut.MP4 -ss 00:00:18.440 -to 00:00:20.440 cut.MP4

2) Cut video while making every frame a keyframe (seems to reduce quality)
> ffmpeg -i unCut.MP4 -ss 00:00:18.440 -to 00:00:20.440 -g 1 cut.MP4