which video editors have great slow-motion effects?

[shun]

I'd like to edit slow-motion videos using high-FPS clips (from my cellphone or other devices). I'm looking for good motion interpolation where the software creates additional artificial frames based on nearby frames, to allow for smoother motion. My old Vegas Movie Studio 10 has this feature, but the software is getting old. What tools or NLE editors will create high-quality slow-motion clips?

Specifically, does anyone know if Adobe Premiere Elements can do this well?

[racer-x]

You can try slowmoVideo. It allows to make slow motion using frame interpretation and even speed ramps. Then import your newly created slow-mo video clip into your favorite editor.

[pippas]

Some of the notes in THIS GUIDE might be useful, if you want to include the idea of 'optical flow' - rather than just simple frame interpolation - to help with smoothness.

This clip : https://www.youtube.com/watch?v=MDCN5srjM_E shows an example of how 'optical flow' differs from the Sony Vegas 'velocity envelope'' frame interpolation technique...

[johnmeyer]

I'd like to edit slow-motion videos using high-FPS clips (from my cellphone or other devices). I'm looking for good motion interpolation where the software creates additional artificial frames based on nearby frames, to allow for smoother motion. My old Vegas Movie Studio 10 has this feature, but the software is getting old. What tools or NLE editors will create high-quality slow-motion clips?

No, Vegas Movie Studio does not have motion interpolation software. Instead, slow motion in all versions of Vegas is done by blending adjacent frames to create the tween frames. This is a completely different way of doing slow motion. The good news is that it never creates weird artifacts, something that is a huge problem when using motion interpolation software like Twixtor. However, since it is simply blending adjacent frames, the resulting video is very, very blurry.

If you want to create slow motion using motion interpolation, there are all sorts of plugins available for AVISynth that do exactly this operation and which work as well as any of the very expensive commercial options.

[shun]

You can try slowmoVideo. It allows to make slow motion using frame interpretation and even speed ramps. Then import your newly created slow-mo video clip into your favorite editor.

That tool's concept looks interesting. I tried it but the rendered output was less smooth than the original and had artifacts. I reduced the lambda value as the documentation suggested but it didn't help. Maybe my ffmpeg settings need adjustments.

Some of the notes in THIS GUIDE might be useful, if you want to include the idea of 'optical flow' - rather than just simple frame interpolation - to help with smoothness.

This clip : https://www.youtube.com/watch?v=MDCN5srjM_E shows an example of how 'optical flow' differs from the Sony Vegas 'velocity envelope'' frame interpolation technique...

Thanks so much for mentioning this tool. I skimmed over the tutorial (I don't think the HQX format and AvsPmod are necessary for this process), but the result is amazing! Any tips on editing the original audio to match the stretched video? I think I could do it separately in my video editor if the slowed speed is constant, but I'm not sure how to do it easily if the new video involves acceleration or deceleration (at least I think that's what the Slowdn function is doing with the "startRatio" and "endRatio").

No, Vegas Movie Studio does not have motion interpolation software. Instead, slow motion in all versions of Vegas is done by blending adjacent frames to create the tween frames. This is a completely different way of doing slow motion. The good news is that it never creates weird artifacts, something that is a huge problem when using motion interpolation software like Twixtor. However, since it is simply blending adjacent frames, the resulting video is very, very blurry.

If you want to create slow motion using motion interpolation, there are all sorts of plugins available for AVISynth that do exactly this operation and which work as well as any of the very expensive commercial options.

Ah I think what they call optical flow is the motion interpolation you are referring to. I think "frame blending" or "frame interpolation" are less misleading terms for what I meant (as opposed to creating no frames at all). And yes, the Avisynth tool I tried is great; it's good that some of the best things in life are still free! If you can recommend other specific plugins, that'd be great too.

[johnmeyer]

Ah I think what they call optical flow is the motion interpolation you are referring to. I think "frame blending" or "frame interpolation" are less misleading terms for what I meant (as opposed to creating no frames at all). And yes, the Avisynth tool I tried is great; it's good that some of the best things in life are still free! If you can recommend other specific plugins, that'd be great too.

Yes, you are correct.

I created a very simple comparison many years ago showing the difference between creating slow motion in Vegas with resample turned on (which blends adjacent frames); then with Vegas' resample turned off (which simply repeats frames); and finally using MVTools2's MFlowFPS function to create what everyone here is calling optical flow (a correct name for it). This video is only a few seconds long:

https://www.youtube.com/watch?v=UEfpP1zZKVs

I did this a long time ago and used interlaced SD video as the source. Vegas doesn't handle the interlacing correctly which is why you see ghosting in the two Vegas slo-mo examples.

[pippas]

Any tips on editing the original audio to match the stretched video? I think I could do it separately in my video editor if the slowed speed is constant, but I'm not sure how to do it easily if the new video involves acceleration or deceleration (at least I think that's what the Slowdn function is doing with the "startRatio" and "endRatio").....

Slo-mo for video can work really well.... Audio - on the other hand - doesn't usually 'stretch' very well at all!......The audio for the demo clips in the guide I linked to above was entirely reconstructed. As it consisted of a mostly sea background sound, that example was pretty easy to insert extra audio to fill the extra time created. Not always so easy of course. Some folk just leave it silent - or add background music. Only rarely does a stretched version of the original audio work well ... and that kind of manipulation is best achieved separately in an audio editor....

[johnmeyer]

Any tips on editing the original audio to match the stretched video? I think I could do it separately in my video editor if the slowed speed is constant, but I'm not sure how to do it easily if the new video involves acceleration or deceleration (at least I think that's what the Slowdn function is doing with the "startRatio" and "endRatio").....

Slo-mo for video can work really well.... Audio - on the other hand - doesn't usually 'stretch' very well at all!......The audio for the demo clips in the guide I linked to above was entirely reconstructed. As it consisted of a mostly sea background sound, that example was pretty easy to insert extra audio to fill the extra time created. Not always so easy of course. Some folk just leave it silent - or add background music. Only rarely does a stretched version of the original audio work well ... and that kind of manipulation is best achieved separately in an audio editor....

I have to disagree on that point. I use Vegas Pro, and it was upgraded about a decade ago to use audio stretching technology that they licensed called "élastique". With the older Vegas sound stretching, if you changed by more than 2-3%, you would get obvious flanging (an artifact that makes the audio sound hollow, like it was recorded inside a tunnel). So, if you use an NLE with that technology, pippas is entirely correct.

However, with élastique you can stretch a LOT, perhaps as much as 2x down to 50% without having the audio sound too bad. And, subtle changes like 5-10% introduce no noticeable (at least to me) artifacts whatsoever.

Of course you have to decide if you really want the audio to match the slower (or faster) video. This actually is seldom done because, when slowed, it makes people seem quite drunk and foolish. While this is funny the first time you hear it, you probably don't want to do it unless you are trying to create some sort of comic effect. Instead, you usually mix some new audio, possibly consisting of the original audio combined with something else. For this, it is important to have a NLE that makes it easy to separate the audio track from the video track so you can operate on it independently. Since Vegas was originally an audio editor to which video was later added, it is especially good for making audio edits on video material.

Here are two examples that I uploaded for another thread a year ago to let you hear the difference between common audio stretching and what you can get with élastique. They each use the identical source clip. One is stretched using the older technology, and the other is stretched using élastique:

Stretch_Example.zip

BTW, if I were to do this example again, I'd choose audio that was NOT recorded with reverb. This one had lots of reverb in the original recording and because that reverb is similar to the artifact introduced by the slow down software, it is difficult to judge how cleanly the audio is being slowed down. So, in this case you'll have to take my word that the reverb in the "good" example is almost entirely from the original audio and was not introduced by the élastique slow down.

Someone uploaded this cut from the exact same LP from which I transferred my own audio, so you can listen to the original here:

https://www.youtube.com/watch?v=v7X0WYwgcGU