Here is a movie processed by a IIR* filter. Essential each frame is blended with the previous frame.
This is the movie without filter:
The key line of the script is
composite -blend 15 new.jpg last.jpg -matte blend.jpg
So imagine a directory full of images. Image001.jpg to Image100.jpg
Each newly processed frame is a blend of the current frame with the previous frame. The parameter -blend 15 you can change from anything from -blend 01 to -blend 99. Play around a bit to understand it better.
The exact script I used is available here on github:
https://gist.github.com/1123061
It’s a bash script and it uses Imagemagick to do the image processing and FFMPEG to make the frames into a movie. Both Imagemagick and FFMPEG are free, open source programs that run on linux, windows and macosx. Plenty of other ways to do the same in other languages as well.
*(Infinite Impulse Response) a technical term for the engineers.
timelapse farm 
Where to find the IIR filtered version? Thanks!
good question. blip is long gone and all those files lost. who said the internet is forever?? this vid has a similar IIR filter on it but is a much higher frequency environment. https://youtu.be/RNe4yf5i4EE
So true! 🙂 Thanks!
On another note, are IIR filters meant to be always a frame blending effect?