[mkgmap-dev] [mkgmap-svn] Commit r572: MDR16 is some kind of codebook.

Sun Dec 19 21:12:27 GMT 2021

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 at lists.mkgmap.org.uk> im Auftrag von Ticker Berkin <rwb-mkgmap at 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

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