If you want to manually set keyframe intervals in FFMPEG, for, say, transcoding to FLV for your online video site, the correct parameter you want is -g <int>. Like most of the ffmpeg documentation unless you’re a video code guru it’s 100% non-obvious, but there it is. I got nice, very dense keyframing for doing things like seeking to anywhere in the video.
Ex:
ffmpeg -i myvideo.mpg -g 1 myvideo.flv
Beware though, the resulting size of the video will vary widely based on a variety of factors, including original codec, length of the original video, frame rate, etc.
