Are there any free ways to increase the framerate of a video? Suppose I have some footage at 30FPS that I'd like to have a copy at 60FPS with tween frames generated by interpolation (at this point I don't care too much about potential quality or artifacts.) And suppose I'm working on a tight budget, so I'd need stand-alone software that's free, or free plugins to other software that's free1. What options are available at this (lack of) price point?

Through my own Googling, the only thing I've been able to find is: Convert videos to 60fps. Unfortunately the software doesn't work for me (after installation, it won't open! :D), and after tons of troubleshooting I'd rather look for a different method.

I know that there are things like Twixtor out there, but right now they're beyond my budget, so any suggestions would be appreciated.

1. I'm willing to hear solutions that do involve money, but the cheaper the better!
what about creating image sequences and then using somehting like ImageMagick to interpolate between the frames.

So (assuming bash, zsh or similar shell) this should work:

mkdir tempdir
mkdir outputdir
ffmpeg -i input.mov -f image2 tempdir/temp_%06d.png #create a png sequence
len=$(ls -1 tempdir|wc -l) #count the files in temp dir
for f in {0..$len} 
do
    old=printf %06d $f #number of current frame
    next=printf %06d $((f+1)) #number of next frame
    new=printf %06d $((f*2)) #number of output frame from current
    newInt=printf %06d $((new+1)) #number of output frame from interpolation
    convert -morph tempdir/temp_${old}.png tempdir/temp_${next}.png outputdir/output_${newInt}.png #create the intermediate frame with imagemagick
    mv tempdir/temp_${old}.png outputdir/output_${new}.png #rename the old frame with a new number and move it to the output dir
done
mv tempdir/temp_${next}.png outputdir/output_${new}.png #move the last frame
ffmpeg -i outputdir/output_%06d.png &lt;&lt;codec etc. options here&gt;&gt; output.mov


basically that creates a temp folder, makes a png image sequence from ffmpeg, creates an intermediate by morphing the two frames into each other using imagemagick, and turns the output image sequence into a movie. 

If this is too slow you could do a quick and dirty interpolation by just blending the two frames together. In that case you'd use 

composite -dissolve 50 tempdir/temp_${old}.png tempdir/temp_${next}.png outputdir/output_${newInt}.png


in place of the convert -morph... line
Obviously you'll need to have imagemagick and ffmpeg installed, and you have to substitute your input and output filenames and preferred output video file format and codec etc options.