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Reading different docs and texts about codecs, I`ve found one strange thing. Many people repeats - "Default params ARE the best!" "Do not change!"
I respect that scientists, who created these `default` values for DivX 4+ codecs. But after some films viewing and coding, I`ve decided to experiment myself.
It costs me week of worktime, week of 4 computers (1.1 GHz and near) worktime, 20Gb disk space. I asked 10 people for attention, and they looked at my products 3-5 days.
Hardware details:
Computers were quick enough. Maximum PostProcessing Level was possible. Really only `ring`-artifacts were less or more recognizable from changing PostProcessing level.
Film effect, when using 5.02 ax filter - the good thing, but I`ve turned it off during my probes.
No cartoons, no 3D-animation, only play movies tested.
I assume, that eyes are important details, and if we see face in the frame, defects near eyes are extremly annoyning, in comparison with errors in any other place of picture.
It is possible to pack classic Video CD with 352 x 288 pixels frame with 280-320-400k bitrate instead of 700-800. And picture quality is kept!
When packing videostream from DVD with picture format 720 x 400 I have kept original picture quality even on 480-560-600k bitrate. In default settings state I have surely detected difference between 640k and 1280k bitrate.
These changes increase subjectivic quality of quick panorames and zooming. If picture are totally changed during 10-40 frames, additional keyframes gives better feeling.
Also you see less quality of tiny water waves (film `Minority Report`, crime scenes in water). If water waves` sizes are near 32 pixels - you see not real waves, but `ring defects` of packing process waving.
These 2 params affects visibility of packing defects on keyframes. Badly drawn keyframe updates to maximum quality in less steps. Note, that original 10 and 20 values cause up to 10 steps of updating, 3 and 6 - maximum 2 steps. 10 frames of updating is too many - 0.4 seconds. Eye detects `bad quality picture`.
Interesting fact is, that authors of some papers detect the visibility of `badly drawn keyframe` in DivX 4 stream (with default codec settings), but 5.02 has THE SAME problem. I think, these authors have not changed parametres from defaults. ;-)
This minimizes number of keyrames to `only-scene-changes`. 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.
DivX 4.12 tuning for comics, slide-show
There are many videomaterials, formed as .avi file, but actually they may
be called `slide-show`. Static pictures with very small changes, music,
rare moving of small details (as in anime).
Example - "Bezhin Meadow", made from one-frame pieces.
Best DivX settings to keep quality and minimize size are: