Slowing down a clip

lynn1102 wrote on 3/9/2014, 6:54 PM

I got a job putting super 8 movie film on dvd. Most of it is pretty good, but as usual, there are sections where the guy does a lot of fast panning. I have already cut out several spots, but would like to save some. Panning on a group of people fast enough so that most on screen a half second. Plus I'm getting seasick watching it. Stretching the clip did slow it down, but now it's all jerky.
Is there a limit to the stretch that works better, or a sweet spot I can try for?
I'm using version 10.0e.

Comments

xberk wrote on 3/9/2014, 7:34 PM

Using a "velocity envelope" on the clip will be more precise as you can see the percentage you are slowing things down and get it adjusted to the best point via trail and error. Using "stablization" might help but will likely degrade the image ..

Chienworks wrote on 3/9/2014, 7:34 PM

A sweet spot would be where the frames of the film line up with frames of the video. Most 8mm cameras shot at 18fps. I'm assuming you're in NTSC-land where the video is 29.97fps. If you slow the movie down to 14.985 then you'll end up with two video frames per movie frame. I'm guessing though that you've already captured the film to video, so that may complicate things quite a bit. To convert 18 to 14.985 you'd have to slow it down to about 0.833 of normal speed. Of course, that's assuming the camera ran at 18fps, and not 17.92 or 18.13 or whatever it might actually have been. Problem is that when it was converted to video you might already have picked up frame blending or strobing that could be made worse by changing the speed.

Do definitely try what you've already done with resampling disabled.

PeterDuke wrote on 3/9/2014, 7:39 PM

If you want to slow down video without jerkiness, you will have to interpolate new frames. Blending frames will do this but they will be blurred. For best results you need something like the rather expensive Twixtor.

See also http://eugenia.queru.com/2009/02/09/butter-smooth-slow-motion/
and http://www.sonycreativesoftware.com/Forums/ShowMessage.asp?Forum=4&MessageID=629373&lang=DEU

Rainer wrote on 3/9/2014, 9:58 PM

Or use AviSynth, VirtualDub and MVtools2, which imo gets a better result than Twixtor. The process used to be a bit fiddly, but Petr Schreiber has made a GUI which simplifies the whole process: get it from thinbasic.com/community/showthread.php?t=12274&highlight=petr

lynn1102 wrote on 3/10/2014, 8:34 PM

Thanks guys. I'll play with it some more. Have been mostly retired and haven't done much video. I remember a lot, but not this part.

Lynn

johnmeyer wrote on 3/11/2014, 1:29 PM

I do a lot of transfers of amateur 8mm, Super 8, and 16mm film. You raise two related issues.

First, with the 16 fps and 18 fps frame rates used by these cameras, any horizontal pan, unless done very smoothly and slowly will result in visual "judder" (apparent jerkiness) because our persistence of vision can still somewhat perceive individual frames at these lower frame rates. This is true even for 24 fps film. If you simply telecine (i.e., repeat frames or fields) in order to increase to 60 fields per second (normal NTSC video), this judder will still be there.

So, if you need to get rid of judder, then the best way to do this is to use a program like Twixtor, or After Effects, or AVISynth/MVTools2, or Motionperfect to synthesize artificial frames in between the existing real frames. You have to know what frame rate you are going to use when you deliver the video, and you then set these tools to change the film to that frame rate. However, these tools are far from perfect, and they can really ruin certain types of motion, such as people walking in front of the camera (the back and forth motion of people's legs gets all screwed up). However, the technology does a near perfect job when the camera is panning across a scene.

What I do is the edit my entire project, setting all events to disable resample. I then render this project to my final frame rate, using a lossless intermediate codec (or at least a high-quality intermediate like Cineform). With resample disabled, Vegas adds the telecine repeated fields during the render.

Then for those portions where the camera is rapidly panning, I do a second render of just those sections, but using one of the tools I mentioned above (and that others have mentioned as well). I then combine these two renders together on a new timeline, with the project properties on that timeline set to my final delivery fps. I then render to DVD or MP4 or whatever my delivery vehicle is going to be.

This is a little extra work, but it completely eliminates the judder on pans.

Now, if your problem is that the camera is simply panning too quickly, so the viewer doesn't have time to comprehend the scene; or if the camera operator did the typical amateur thing of wandering back and forth, then changing these scenes using slow motion can sometimes help. The tools several of us have now mentioned can give you very good slow motion.

One other idea: you might also try using the motion stabilization in Vegas (ProDad Mercalli). It can sometimes tame the wildness in wild panning and make it easier to watch.