How to combine Videostreams with differing framerates

I want to edit a video of a concert of ours where we record with different cameras. Unfortunately, we don’t have several cameras of the same type available, but are filming with cell phones, GoPro and video cameras.
Even though we set 30 FPS on the cameras, unfortunately the framerates of the cameras are not exactly the same. A cell phone outputs the stream as 29.9, the iPhone as 30.02, etc.
Since we record the sound separately and music and video should of course run exactly in sync over the entire length of the three-hour concert, I would like to know if there is anything we can adjust here in Shotcut.
I would like to avoid double images or missing single images, which sometimes occur for padding or adjusting.
Converting the individual streams with an external program would not only take a long time, but probably also degrade the quality.
What is the best thing to do here?

I would be very grateful for any help. Thank you.

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I would not worry about the tiny difference in frame rate. The difference is too small to notice an infrequent frame slip. This is especially true for content that has low motion like a concert. I recommend to try editing the clips and see how you like the result. Just be sure to set the video mode to one of the frame rates: 30.00 or 29.97.

They will almost certainly not stay in sync for the duration of a 3 hours concert. Each recording device will have a slightly different clock.

I recommend that you try the Align To Reference tool.

For 3 hour clips, it might take a very long time to run. I have never test it for such long clips.

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Thanks for your answer. I’ll probably just have to wait and see how much the picture and sound diverge after a while. So maybe it will be best to always synchronize sound and picture again at the beginning of a new song.
Do you have any experience with what the program does when you mix video streams at 30 fps and some at 25 fps? Does this cause problems already during editing or only during output?

Sorry for asking such beginner questions. But I am quite new with the program and get along quite well with it. But that now in the concert recordings these differences of the video streams occur, I could not foresee :blush:

For 25 → 30, Shotcut will duplicate frames for both preview and export. Going the other way will drop frames.

I have been able to take footage from three different Panasonic cameras (two G85 and one GX85) that ran for three hours, and all three of them required only one sync at the beginning and stayed in sync until the end with no problems. But those are real cameras. When a cell phone is added to the mix, it’s game over within minutes. Cell phones are very frustrating for multi-camera work. There is a chance that things have improved with ProRes to SSD on the iPhone 15, but I have not tested it or heard any reports about how accurate the clock is for multi-cam work.

For fast motion, the conversion will result in motion that is not smooth. For slower motion content, it may not be noticeable. I would expect a concert to not have very fast motion. Why not try it out and see how you like it?

Shotcut does not care what the frame rates are and will not have a problem. But maybe you will not be happy with the result. That depends on your own opinion and you can only know by trying it.

the best is to conform the videos to avoid any problems, particularly jumps (certainly not visible given the differences in FPS) Software is specialized in this conformation step)

Is there software You could recommend?

In any case, I’ll do a video test before the concert. Because if the result of the 25 fps camera in combination with the 30 fps cameras is not good, I would try to exchange this camera beforehand. Otherwise, I might have nice in the shots, but can’t use them because of technical issues.

It seems to me that it is quite common in the industry to not have identical cameras on several technical points including raw color rendering and also FPS…
This is why conformation (conformer in French, I think the verb is the same in English to conform) exists and is practiced.
I use the great tool developed by a Frenchman Paul Pacifico; the software is extraordinary, a toolbox.

Thanks for the information.
In the meantime I have edited a test video and am very impressed what Shotcut makes out of two different video streams (50i and 30) as a result. So, in a pinch, that would also work. But all cameras with the same frame rate is of course ideal.

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