Progressively Accelerate Video with ffmpeg

Question

I'm currently trying to make a time lapse video. This can be done fine with iMovie, however, I'm having one simple issue. Is there any way to accelerate a video progressively with any open source software?

I specifically named ffmpeg, because I've always had the feeling ffmpeg can do anything :). However, if there is any other (free) alternative, I'd be quite glad to hear of it as well.

If you want to know why, I want to progressively increase the speed to give a dramatic effect to my video.

Essentially, I want the video to get faster as it progresses.

Answer 1

If you have a Linux machine with an nVidia card you might try this: http://slowmovideo.granjow.net/

I've been using slowmovideo. It's still very much alpha software. However, I've been getting some pretty impressive results.

I also progressively speed up video using Blender VSE. Just like slowmovideo, blender lets you change the video speed by manipulating an IPO curve.

Answer 2

if i unterstood correctly - you are asking for a speed-ramp? check this out, and tell us if it works for you:

ffmpeg -y -i 15.mp4 -filter:v "setpts=(1.5-0.002*N)*PTS" new.mp4

this ist the movie making slow to fast, and the other one from fast to slow:

ffmpeg -y -i 15.mp4 -filter:v "setpts=(0.003*N+0.5)*PTS" new.mp4

where N is the framenumber starting at 0 to the max of 30fps*15seconds = 450.

The numbers 1.5 and 0.002 and 0.003 and 0.5 are parameters to change for your belongings, it tells at which speed to start, which speed to reach and how fast.

For more details look at the ffmpeg-filter-documentation

Answer 3

DaVinci Resolve free version can do variable speed control on a clip if this is what you're after i.e. for the duration of the clip, it's playback speed changes gradually from A to B.

If your video is missing frames e.g. due to excessive slow down you can even make it insert generated frames by using the "Optical Flow" feature.

Answer 4

If someone wants to do this on a Mac, here's how.

Download the free trial of Final Cut Pro X (it's 30 days).

In Final Cut Pro X, you have two options that essentially do exactly what SlowMoVideo does:

• Optical Flow (the creation of frames based on the direction pixels move), for smoother slow motion.
• A Retiming Ramp, which lets you either gradually go to 0% speed, or from 0% speed.

Answer 5

I think you could script it. For each picture, make a video of only this picture, but make the time show sorter and sorter. After all pictures are processed, then concat all the videos into one video, where each picture will now be shown a shorter and shorter time.

Answer 6

Render your movie as series of images. To speedup your timelapse simply delete every other image. Then combine rest of images with ffmpeg like this: ffmpeg -i image-%03d.jpg foo.avi

Answer 7

Neither Kdenlive nor Shotcut can do speed ramping, but here's a workaround:

1. Have the two clips next to each other. The transition will transform the last 7 seconds of the first clip into 3/8s, and the first 7 seconds of the second clip into 3/8s, for a total transition time of 6/8s.
2. Seek to the end of the first clip.
3. Seek back 4 seconds, and split. Set the speed of this 4s clip to 32x.
4. Seek 2 more seconds back, and split. Set the speed to 16x.
5. Seek 1 more second back, and split. Set the speed to 8x.
6. Repeat steps 3, 4, 5 in reverse order for the second clip. I.e. Split at 4, 2 and 1 seconds, and set the speeds to 32x, 16x, 8x.
7. Remove the blank spaces between the clips.

Note that each of the ramp sections lasts for 1/8 seconds: 1s @ 8x, 2s @ 16x, 4s @ 32x <-- for the first clip; the second clip will have 18/s second sections in reverse order: 4s @ 32x, 2s @ 16x, 1s @ 8x.

Note that due to a bug in Shotcut, you may see extra frames. You'll have to remove those manually.