Recording of Lectures: Tips for compressing video with mostly still images I have several recordings of lectures, some with powerpoint slides, some with writing on a blackboard. They are several GBytes each. However most of the time the video is a still image (besides maybe some movements of people, occasional shaking/adjustment of the camera).

How can I compress the video effectively without loosing sharpness and the audio? I thought about making the frame rate super low (say 1fps, or even less). Even better would of course be something that analyzes the change in the image and only updates if the image changed by a certain amount.

The output format doesn't necessarily need to be a video, something like a html format or a ppt/libreoffice presentation would be fine too. However the Audio should be in sync with the images, and it should not require an exotic software to play it back.

I think I could program something that does the job, but I would really prefer to just use an existing software, dump my video file into it and get the result out. Who has suggestions? Did anybody try something similar?
Cross-platform or Linux solutions are preferred :)
H264 is actually a pretty good codec for such content. Its based on motion vectors and you can define in which intervals the codec should encode a full frame, everything in between will be based on the last and next keyframe (simplifying here).

x264 is probably the best h264 encoder out there and luckily open source. Probably the best way to use it is through ffmpeg (open source, cross-plattform).
Here is a good general guide for x264 and ffmpeg:
https://trac.ffmpeg.org/wiki/Encode/H.264
Especially take a look at the -tune option, it has a preset for still images, so perfect for you.

And this guide shows some of the advanced options like keyframes/GOPs.
https://sites.google.com/site/linuxencoding/x264-ffmpeg-mapping