10/21/2009

10-21-09 - The Day's News

ADCTC is the best published image compressor. It's a pretty obvious jamming together of various old ideas. It uses DCTs of various sizes for transform, up to 128x128 and allows non-square partitions. It picks optimal partitions like an old "Wavelet Packet" coder. Then the DCT coefficients are coded very much like ECECOW using a context coder with big contexts (ADCTC doesn't actually code bit planes like ECECOW does, it codes significance and top bit position, but uses contexts similar to ECECOW; the older verison AGU is really just like ECECOW/EZDCT).

DLI appears to be the best image compressor now. He's released zero info about it. So fuck him.

Twitter image compression challenge is cute.

I made new compiles of the LZP exes (as a I posted about before) ; they should not crash now. Back in the Amiga days I would always write my string matchers without bounds checks, because reading out of bounds was not an access violation, and then I would clamp the length after the fact. That is, rather than something like :


for(i =0; i < maxLen && ptr1[i] == ptr2[i] ; i ++ ) ;

I would just do

for(i =0; ptr1[i] == ptr2[i] ; i ++ ) ;
i = MIN(i,maxLen);

(this is simple pseudo-code to make the point, not actual code).

That doesn't work any more now that reading outside of the allocation is forbidden (there are ways you could make this style of thing still work of course, by allocating extra space off the end, and then concatenating a sequence that does not occur in the original text; I'm not sure if there's a very simple/fast way to find a sequence that never occurs in the original text).

Anyway, this was because the Squeeze Chart guy tested the old LZP's ; it's kind of amazing that they're still vaguely competitive in terms of speed/quality, though the more modern variants of course do better (such as Yann Collet's "LZP2" and of course higher compression LZP variants like the stuff by Ilia Mureyev etc. from compression.ru)

In other news :

Said the Gramophone is a good music blog.

From Busto to Robusto is a pretty nice poker show about real internet poker. (2 Months 2 Million is a fucking clown show)

George Nakashima is a fine wood furniture maker from Seattle. In the 50's he did seminal work creating simple furniture which explored the natural grain and shapes in the wood, letting it speak for itself. It's rather old hat now as so many cheezy places like ABC / DWR copy the Nakashima style, but the originals still have a profoundly elegant combination of understated refinement and untamed natural forms.

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old rants