Making video into timelapse, but adding frames

[oggologgo]

I have a long video, which I need to make into a timelapse, but for this particular video I don't want to just skip frame and use example every 10th frame. Instead I want to ad/merge every 10 frames into one.

Anyone knows of software/filters that can do this?

[filmboss80]

I'm assuming that your goal is to smooth out the motion, but you are going about it the wrong way. If you layer 10 frames onto one (Photoshop could do it frame-by-frame, with one frame incorporating 10 frames, each on their own layer with transparency), you'd just end up with a blurry muck.

Better to do one out of 10 frames, then go through a second stage, morphing an intermediate frame between frames to help smooth out motion. (STOIK MorphMan may be a place to start.)

[jagabo]

If you layer 10 frames onto one (Photoshop could do it frame-by-frame, with one frame incorporating 10 frames, each on their own layer with transparency), you'd just end up with a blurry muck.

It depends on how much motion there is in the frames. With no/little motion the frames will remain clear. With a lot of motion they will get blurry.

AviSynth can blur frames together with Overlay() or Merge(). You could also use multiple passes of some of the temporal smoothers or Average() followed by decimation. Here's a sample script using Average():

v1=AviSource("Video.avi").ConvertToYV12()
v2=Trim(v1,1,0)
v3=Trim(v2,1,0)
v4=Trim(v3,1,0)
v5=Trim(v4,1,0)
v6=Trim(v5,1,0)
v7=Trim(v6,1,0)
v8=Trim(v7,1,0)
v9=Trim(v8,1,0)
v10=Trim(v9,1,0)

Average(v1,0.1, v2,0.1, v3,0.1, v4,0.1, v5,0.1, v6,0.1, v7,0.1, v8,0.1, v9,0.1, v10,0.1)
SelectEvery(10,5)
AssumeFPS(framerate(v1))

That will give you a 10x increase in playback speed where each frame is the average (equal weighting) of 10 source frames. Attached is an example video (Xvid AVI).

[oggologgo]

Thanks, but I know what effects adding the frames will give, and that is what I want.

Would it be possible to do it with a script for AviSynth? I am not into AviSynth, but if it can be done that way, I'll learn it.

I case you are curious, what I need to do it this way for is two things. One, I have an hour long video of fireworks from newyears eve, and I want to keep the trails after the fireworks, and not lose them by cutting out some frames. The other is for making a timelapse of the stars passing over, where adding the pictures is a normal method to use instead of long exposure. In both cases the camera is on a tripod, so there's no other movement than the movement I want.

[filmboss80]

For the fireworks, you're better off doing a series of multiple dissolves (aka crossfades); timelapse would make the duration of the explosions too fast--like quick, flashy pops on the screen. As for the stars, keep in mind that layering and combining frames may cause the stars to "streak," instead of being tiny, pinpoint dots that move.

How are you shooting the stars, anyway? In order to get them to show up brightly, you won't be able to avoid a timed exposure, as they are so dim. Most filmmakers dealing with timelapses of stars actually use film, not video. Each frame is exposed for several seconds before advancing to the next frame.

[jagabo]

With the two proposed uses you'll have brighten up the videos after averaging. All the black background will darken the small fireworks and stars when averaged over frames. You may have to add frame rather than average them. Overlay() can add.

[oggologgo]

jagabo, thanks for the sample script. I will be using that, except in both cases, I do need to add instead of merging though.

filmboss80, you are right about the crossfades for the fireworks being better. For the stars, I'll use short enough intervals though for streaking not to be a problem.

Thanks for the help. AviSynth is what I'll be using.

[jagabo]

I'd love to see some sample clips when you're done.