Larger AVI files take much longer to process than smaller ones. Why?
The obvious answer is “Because they’re bigger”. The real answer has to do with the way AVI files are constructed. AVI files contain video streams which are composed of “key” frames and in-between frames. A key frame is a whole image frame. It is (usually) compressed, but contains all the information required to reproduce a single frame of video. These frames are spaced throughout the video sequence, usually evenly. In-between frames are all the frames that occur between key frames. These frames are not stored as whole frames but are actually changes to make to the preceding frame. To construct an in-between frame, you need to build off of all previous frames back to the nearest key frame. Ex.
