Reported mp4 duration does not include the final frame

[glenne]

The MP4 track duration appears to be set to (frame_count - 1) / 60 rather than the correct frame_count / 60.

The review app uses the actual embedded timestamp so gets the right answer but other calculations like seeking for a time need the correct fps value. The review app will check adjacent frames when looking for a specific time so is robust in spite of this.

Verify with ffprobe file.mp4 and look at the Stream#0 line which will report a number slightly more than 60fps. The longer the recording the less it matters.