[Marcin Lipiński]

So I understand that FCPX uses a simple frame-to-frame conversion. For sure? So… what are the different frame matching options for? Besides, not all clips work like this. For example: sound from the voice recorder + Panasonic camera (50 fps) + Sony A7RIII (24 fps) + old Sony 29.97 fps camera … everything placed on the timeline agrees (Project for example 25 fps!) — the recording time from one device is exactly one hour from another device. Except for this one recording from Sony A7s. Besides, it seems to me that the speed of the film does not depend on fps. This can not be true. The program should match the clips mainly according to time, that is, the hour equals one hour. I understand the issues of different frames in a second, but such an advanced program should convert the frames while maintaining the recording time. This is followed by various options for matching frames. Am I wrong?

[Marcin Lipiński]

I was wrong to give a link. Excuse me. A similar problem is described here:
https://forums.creativecow.net/docs/forums/post.php?forumid=344&postid=32050&univpostid=32050&pview=t
But I will try to describe the problem more simply.
I have two clips. One recorded with a Sony A7s camera at 23 fps, the second recorded Sony A7RIII at 25 fps. Suppose this is a recording of a falling ball. When I put these two clips in iMovie, I do not have to do anything. If I arrange the clips so that their origin is in the same moment, they are synchronized along the entire length. The ball falls at the same moment. In other words, if I manually synchronize the clips, it’s all pretty, until the end is right.
Meanwhile, the same clips placed on the timeline in the FCPX are played at different speeds. On one the ball moves faster, and on the other slower. If I wanted to synchronize these two clips, I would have to slow one down to 95.9 percent of the speed. Why is iMovie doing it right, and the more expensive and professional FCPX does it wrong? Where is the reason?