--> sudo apt-get install mencoder


mencoder -nosound -ovc lavc -lavcopts vcodec=mpeg4 -o test.avi -mf type=jpeg:fps=20 mf://@files.txt

This will encode all the files listed in files.txt into a movie called test.avi using the mpeg4 encoder with no sound and a framerate of 20 frames per second. 
Messing with the fps gives very different results. See “Encoding from multiple input image files” in the mencoder documentation for more info.

Here’s an example video made using this method:

    I used this to create my timelapse videos and thought I’d post my finished (and working) product. The first line finds all files older than 720 minutes and 
puts them in a list as you described. The second line encodes it. The third converts it from an .avi to a .flv format. I hope this will hope someone!

    find /var/motion/elp/data/archive -maxdepth 1 -cmin -720 -type f -name *.jpg -exec ls -1tr {} > /var/motion/elp/data/archive/webcam.txt \;

    mencoder -nosound -ovc lavc -lavcopts vcodec=mpeg4 -o /var/motion/elp/data/webcam.avi -mf type=jpeg:fps=10 mf://@/var/motion/elp/data/archive/webcam.txt

    ffmpeg -i /var/motion/elp/data/webcam.avi -b 800k -s 640×480 -r 10 -y /var/motion/elp/data/webcam.flv