How to mix different FPS movies on VSE.

Tutorials, Tips and Tricks
1

EDIT: 2.77 includes this new feature: “Strips - Importing new movie strips now uses movieclip framerate”
So, maybe this trick is not usefull any more (I’m just downloading 2.77 right now, I’ve never try it)

As a suggestion, the source movies have to be the same framerate as the final framerate. But, if we have different framerate movies, we have to do some tricks…

First, we select the final framerate, for example: 29.97 (29,97002997). Then, we import the movies. If the movie framerate is, for example, 30fps, you have to:

  • Select the movie track.
  • Add “Effect Strip” - “Speed Control”.
  • Make sure that “Use as speed” is checked and change the Speed Factor. In this case, the movie is 30fps and the final will be 29.97. So:

Source framerate / Final framerate = Speed factor
30 / 29,97002997 = 1.001 (check http://en.wikipedia.org/wiki/NTSC)

  • “Speed Factor” would be 1.001.

AUDIO

Now, the movie speed is fine. If the movie has no audio, it’s done. But, if it has, we have to change audio speed. We won’t do it with “Speed Control”, but with “Pitch” option, in audio properties (I think it should be named “Speed” or “Time stretching with Pitch”). We change to 1.001, too.

OTHER FPS

If the movies framerates (source and final) are different, we have to calculate. E.g.:

24 / 30 = 0.8
15 / 30 = 0.5
30 / 24 = 1.25
30 / 15 = 2
24 / 29.97 = 0.8008008008… (*)
…

(*) Blender stores values with 6 decimals in Speed factor. If you input 0.8008008008 (10 decimals), you will see 0.801. But, internally, it is 0.800801 (6 decimals). I didn’t test it, but I think it is far enough.

There is another way to do it: uncheck “Use as speed” and enter keyframes at start and end. The first, has to be 0 (or 1) and, the last, a “calculated last keyframe”:

Source total lenght: 2880 (2 minutes at 24fps).
So… 29.97 * 2800 / 24 = 3596.4 (Cross-multiplication)
Final total lenght: 3596.4.

WHEN CHANGING TRIM DURATION OPTIONS

But, be carefull using keyframes with Speed Control… because, if you change source movie Trim Durations (soft or hard) to change the start of the movie, the Speed Control moves itself automatically to the start of movie… and, in this move, the keyframes do the same. You will have move keyframes by hand.

2

Of course a large change in pitch can sound funny too.

3

Yes, for that, you can use the free program Audacity and its “Paul Shift” effect to change the length of something without effecting its pitch (too much, anyway).

It’s funny about changing frame rates: For movies switched to Europe and Australia’s “PAL” format, they were sped up a little bit from 24 frames per second to 25 (so 25/24, which leads to about 4%). I was recently watching a rip of ‘Batman’ and, during the opening music (which I’ve heard a billion times in my life), I was like, “Man, that sounds just a little bit off. What’s up?” So, I checked the length of the video: 2h1m. Then I went to Amazon and saw that the original movie is 2h6m. So even that tiny bit of speed-up was discernible. (Of course, as I said, I’ve heard that music so many times that it’s not surprising in this case. For other movies, I probably wouldn’t notice.)

4

I know that the podcast Friends In Your Head, where they provide an alternate commentary track to movies, they have to release PAL versions as they commentate to NTSC discs. That is a slightly sped up version.

I never notice it, living in Australia but there should be a difference from the cinema (at 24fps) and home (at 25fps) I guess.

5

@DavidBrennan, read again the Audio part. I explain what happens to audio. There’s no need to use Audacity or any other program. Blender has its own Pitch option.

Yes, I know this is an ooold post…

6

I think Audacity will do a duration change with a corrected pitch however, while Blender naturaly gets squeakier as the frequency increases (clip shortens).

7

Sorry guys… there’s a lot of time I don’t touch it. Yes, you are right, the frequency is also modified.

I reported a suggested name changing here: https://developer.blender.org/T45441?workflow=create

8

Very handy info, thanks!

9

I made an addon for this. Blender 3.0 required.

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