I added a new section to my book. http://mattmahoney.net/dc/dce.html#Section_438

I haven't tried Crinkler but I did think the description was interesting. It is essentially PAQ1 with sparse models, static weights tuned by the compressor, and a E8E9 filter all packed into 210-220 bytes of x86 code. It is for compressing self-extracting demos (programs under 4 KB).

I linked to a longer description, but the short version should be sufficient for those familiar with compression.