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

Wed Dec 15 17:35:05 GMT 2021

Hii Ticker,

reg. MDR16: When I print the encoded characters which require 8 or more bits in the order of the Huffman tree
they build a sequence which appears at the end of MDR 16 (last 60 bytes or so).
Those chars which are encoded with fewer bits are still a mistery to me.

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen at hotmail.com>
Gesendet: Mittwoch, 15. Dezember 2021 13:07
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev]       [mkgmap-svn]    Commit  r572:   MDR16   is      some    kind    of      codebook.

Hi Ticker,

it's almost impossible to guess when there is only one entry in MDR 30/31 and only one occurence of the code
"00000000000000000000".
I used '#' in my debug code to mark an "unknown" char.

A possible meaning could be that 30/31 are common prefixes and 32/33 are common suffixes in road names.
I doubt that this is related to the Huffman encoding. Maybe the code "00000000000000000000"
simply represents a special character that is replaced with a corresponding string in 30/31?

No idea how that would work with the suffixes.
Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Ticker Berkin <ticker at jagIT.co.uk>
Gesendet: Mittwoch, 15. Dezember 2021 12:47
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev] [mkgmap-svn]  Commit  r572:   MDR16   is      some    kind    of      codebook.

Hi Gerd

Do you think there might be some form of escape sequence that is
followed by a ref to the clear road names in Mdr 30..33. I noticed when
looking at MapInstall manipulated Mdr that the '#' sort got changed.

Ticker

On Wed, 2021-12-15 at 11:13 +0000, Gerd Petermann wrote:
> Hi Ticker,
>
> this is what I have so far. The non-printable characters 0x01..0x04
> are probably not correct.
> Note the special case with the last sequence. It only occurs once in
> the
> index and may as well be an error in the data.
> My code doesn't detect any unknown codes, so I think MDR16 must
> somehow contain this information.
> The character ž seems to appear both in upper and lower case?!? Might
> be wrong.

_______________________________________________
mkgmap-dev mailing list
mkgmap-dev at lists.mkgmap.org.uk
https://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
_______________________________________________
mkgmap-dev mailing list
mkgmap-dev at lists.mkgmap.org.uk
https://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev