Techniques for compressing a slideshow presentation video?
x264 is the best-in-class encoder for generating H.264 video streams and you can use it via ffmpeg, a command-line tool, to encode to a small-sized file. Get a binary from here - opt for the latest nightly/snapshot release - and run

ffmpeg -i input.mov -c:v libx264 -crf 23 output.mov


The output will be the same constant frame rate as the input but x264 is very good at minimizing space consumed by frames which are the same as preceding ones. Lower CRF values produce better quality files at the cost of larger file sizes. 18 to 28 is a decent range to stick within.