Keyframes
Keyframes, are the pictures you see when you fast forward through a DVD. They are inserted by one of two methods under MPEG-4.
- Max Keyframe interval - typically this is done by multiplying the framerate of the movie (e.g. 23.976 or 25 or 29.97) by 10 (e.g. 240, 250, 300), to deliver an automatic keyframe insert every 10 seconds. Typically left at the default value under DivX.
- Keyframe threshold - this intelligently tracks the percentage of blocks not tracked by the motion search algorithm. Typically it is best left at 50%, but can be varied between 40% and 60%. For example, at default, if more than 50% of blocks have changed between frames, a new key frame is inserted.
Read more about this topic: Dr. Div X