These recomendations are not absolute. Earlier I've tuned DivX 4.12 codec better, than it's standart settings. XviD standart settings are better 'tuned', but some trivial changes MUST be done to get better result for some appropriate videomaterial.
I work with VCD/DVD original, NOT with VHS/TV sources.
This minimizes number of keyrames to 'only-scene-changes'. Default forced keyframes per 10 sec (300 default settings) makes less bitrate for other part of stream. Difference may be measured in quantizer levels viewing analyse.log. You may gain even 2 quantizer levels.
But large keyframe interval make inconvinient travelling over time axis in any player. :-(
So - if you prefer to choose position smoothly - make this number less. I prefer to see film as normal film - from beginning to the end.
