Speedig up video - alot

[Cralis]

I would like to film clouds, and speed the video up to get the mice coud movement effect. So, I have ahot at video of 15 minutes, but would like it to run about 15 seconds. Is can maybe avidemux or ffmpeg do this for me?

[Cralis]

Is this not possible with these tools? Maybe a different tool?

[jagabo]

What's the frame rate of your source?

If you want an AVI file you could use AviDemux and its Resample FPS function followed by AviFrate. Set the new FPS to 1/60 the source video's frame rate. That will give you a video with 1/60th the frame rate, the same running time. Then use AviFrate to change the frame rate back up to the original frame rate. For example, if your source is 30 fps, resample to 0.5 fps. Then use AviFrate to set the frame rate back to 30 fps.

If you know how to use AviSynth you can do the equivalent with ChangeFPS(n/60) and AssumeFPS(n). Using the above 30 fps video as an example:

WhateverSource("filename.ext")
ChangeFPS(0.5)
AssumeFPS(30)

[Cralis]

I record in HD format on my JVC Everio. So, not 100% sure what the framerate is. 30fps? I'm PAL.

Which of those methods is easiest. I tried to change the frame rate using Avidemux to 99, but that didn't do anything at all, except make the picture stranger than the original...

I have not used avisynth before...

[guns1inger]

PAL is 25 fps or 50 fields per second.

It depends how smooth you want it. I compressed an hour down to 2 minutes using avisynth scripts. For the most part it was done by shedding frames in multiple passes, then smoothing the result with changefps/assumefps in the final pass. It worked for what I needed.