pouët.net

@break: Screenmode is dynhires interlace, 16 colors of which 14 can be changed in the hblank. Color 0 is left black and some pictures have 1 or 2 fixed colors for aesthetic reasons. I do not calculate 14 fresh colors each line, but constantly reuse a K-Means' state. Input is a density function over line histograms with current line in the center. The K-Means is enhanced with motility/inertia factors per cluster, which are updated/fed-back from the number of pixels represented by them, so clusters have strong tendency to change little, sort themselves by popularity and into the same palette indices. So I get tightly packed line palettes (often only a handful minimal changes per line), and after render/dithering, 4 bit color indices. As Blueberry suggested, the color indices then undergo Move-to-Front transformation before entropy encoding. This idea saved the project 1 week before Deadline, but luckily we also had a canonical encoder and fast 68k Huffman decoder lying around, and MTF transformation is no big deal with only 2.7 bits per pixel on average. (The first picture is unpacked for getting the show up as quickly as possible, this drags down average compression.) The sync is factored around almost constant decrunching, the exact images and order were given by the art department. The music is a regular PT mod.

Minor fix available - now loops on real diskdrives without lambasting the stepper motor (this went unnoticed when coding against an USB drive, now I got hold of an Amiga with a real diskdrive again).