Hi Ticker, my thought for the struct bytes was that the 1-bits might represent the position of leafs, but the bit counts don't match. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Ticker Berkin <rwb-mkgmap@jagit.co.uk> Gesendet: Sonntag, 19. Dezember 2021 10:12 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] [mkgmap-svn] Commit r572: MDR16 is some kind of codebook. Hi Gerd It looks like the order of the letter patterns approaches canonical Huffman (but not quite as far as I can see). With this, only the number of codes of each length is required to form the tree. The "struct for {level}" looks like 2 numbers. Both increasing as levels go from 20 to 6. The first, a single byte from #00 to #3d - this could be give the accumulated lengths at each level (but I didn't get it to match). The second, variable length, from #000006 to #180c00 and I've no idea what it could mean. Levels 1 - 5 seem to be handled differently. with the repeat * 4, repeat * 2, no repeat and the padding. Ticker _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk https://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev