I was trying to convert a Quicktime screencast (saved as .mov) to a format my professor could more readily use. For those who don’t know, FFmpeg is an amazing tool with a wide range of applications, including converting between video formats and ripping audio from a video. Anyway, this took me a little to get quite right (and maintain output quality) so I thought I’d post it here both for others and a place to save it for myself. Although it looks really simple in hindsight:
ffmpeg -i screencast.mov -f avi -vcodec mpeg4 -sameq -ac 2 -ab 128k screencast.avi
It is necessary to specify a video codec because AVI can be used with multiple codecs. To maintain video quality use -sameq. When converting screencasts, it may also be useful to crop out parts of the screen since Quicktime only does full screen capture. For this, you can use the -croptop, -cropbottom, -cropright, and -cropleft arguments. Last, make sure the arguments come before the output file; otherwise they are not applied.
Maybe I will later do a more full post of the different ways I use FFmpeg. But for now, that is all.