Using 29.97 fps and 30 fps clips in same project?

I’ve tried searching for this question and I haven’t really seemed to come across an answer to my particular situation.

I’m still very new to video editing so my Shotcut projects are very basic…

  • I use different clips online + detach/delete the audio + add music

My question is how do I deal with clips with different fps?

For example: My current Shotcut project has 5 different video sources.

2 of the video sources are 30 fps 1920x1080
3 of the video sources are 29.970030 fps 1920x1080

I am not seeking perfection, but, I was hoping someone could help me understand what I’m dealing with and what (if any) sacrifices I’m going to to need to make and how to approach this.

A few questions regarding this:

  • What fps timeline to work in, 29.97 or 30 fps?
  • Will exporting in 29.97 fps glitch the 30 fps clips?
  • Will exporting in 30 fps glitch the 29.97 clips?

If this has already been discussed ad nauseam, I apologize and if some one could link me to another thread about this I’ll read it. Any input is appreciated!

In my opinion the best thing to do would be to set the video mode to 30fps. Put the 5 clips on the timeline, clip them so the timeline is a couple of minutes long. Export this short video and watch it.

If you see any glitches then you might want to do something like @Austin proposed in his post below - convert the 29.97 fps clips to 30 fps and use “Blend” for the frame-rate conversion, then try the short export again and see if this is acceptable.

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The two frame rates will differ by one frame every 33 seconds. Depending on whether the timeline is going slower or faster than the source clip, it means that one frame will get skipped or duplicated every 33 seconds to make up the difference. This will probably not be noticeable 98% of the time. There is also a chance that the drop/dupe frame isn’t even seen if there are enough jump cuts to not reach the 33-second mark in a clip.

With that in mind, I would consider creating the project in whichever frame rate had the most footage time-wise, as that will create the fewest frame drops or dupes in the non-matching footage.

If you do run across a frame dupe/drop that is glaringly obvious, or you decide you want perfection after all, then the post by @Elusien is a decent fix, and could be done on a per-clip basis to save conversion time.

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If you’re happy with FFmpeg, you can change the video and audio Presentation Time Stamps on the 30000/1001 fps (it’s not exactly 29.97) to display each frame at 30 fps.

You would need to do something like:

ffmpeg -i -filter_complex "[0:v]setpts=0.999000999000999*PTS[v];[0:a]atempo=1.001[a]" -map "[v]" -map "[a]"

No one will notice the slight audio change (unless you’ve got 1k tone) or speed change.

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There are several options for using different frame rates.

    • Use video clips “as is”. If the project is set to 30 fps, then the video clip at 29.97 frames will still be smooth, only occasionally and in rare cases will twitching be noticeable due to the fact that sometimes frames have to be duplicated.
    • In the “properties” tab in the “speed” field, you can set the speed to 1.001, this will speed up the video to the desired 30 fps, but there may be problems with sound. In order to find out the speed you need to enter, use a simple formula: 30(desired frequency) / 29.97(video clip frequency) = 1.001001001001001 (acceleration factor), which can be rounded up to 1.001.
    • You can use the built-in video converter in shotcut with the settings that I have given in the screenshot. The advantage of this method is that you will get the smoothest possible image without interfering with the sound. There are also disadvantages of this method - sometimes artifacts of the frame prediction algorithm may appear and the encoder will work very slowly with such settings. I recommend cropping the right part of the video first, and after that, encoding to the right frame rate, otherwise it can take forever.
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Thank you for clearing this up for me. The project was comprised of mostly 30 fps footage so I went ahead and set the video to 30 fps. The 29.97 fps clips were mostly all under 33 seconds so I exported the project and I could not notice anything irregular.

I’ll post the video once I upload it to youtube and timestamp the 29.97 parts for anyone interested.

I bookmarked your post that Elusien linked above, I’ll definitely reference that in the future.

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