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

From Gerd Petermann gpetermann_muenchen at hotmail.com on Tue Dec 21 16:49:29 GMT 2021

Hi Ticker,

looks good.
With your hints I was able to write a patch for MdrDisplay
that seems able to decode compressed mdr15 for my
maps which have mdr 16 section.
Maybe you have another map...

It also changes some details for mdr 30/31 and 32/33.
Open problem is the length of the gap between the end of data for the 6th level and the first bytes for level 5 (prefix 0b).
I see either 7 or 12 or 5 bytes. Check the code that calculdates value for variable skip.
The values might not at all depend on the depth of the tree.

Code is not at all optimized, it just started to work for me.
Lots of bytes in MDR 16 are ignored.

Gerd





________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen at hotmail.com>
Gesendet: Montag, 20. Dezember 2021 11:29
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev]       [mkgmap-svn]    Commit  r572:   MDR16   is      some    kind    of      codebook.

Hi Ticker,

yes, with your theory I found errors in my code. Here's the corrected version
                                // depth 3, prefix 0x07
                                addHuffmanNode("111", 'A');

                                // depth 4, prefix 0x09
                                addHuffmanNode("0111", '\0'); // 0x00
                                addHuffmanNode("1000", ' '); //0x20
                                addHuffmanNode("1001", 'E');
                                addHuffmanNode("1010", 'N');
                                addHuffmanNode("1011", 'O');
                                addHuffmanNode("1100", 'I');
                                addHuffmanNode("1101", 'R');

                                // depth 5, prefix 0x0b
                                addHuffmanNode("00101", 'C');
                                addHuffmanNode("00110", 'S');
                                addHuffmanNode("00111", 'D');
                                addHuffmanNode("01000", 'T');
                                addHuffmanNode("01001", 'M');
                                addHuffmanNode("01010", 'V');
                                addHuffmanNode("01011", 'J');
                                addHuffmanNode("01100", 'K');
                                addHuffmanNode("01101", 'L');
                                // depth 6
                                addHuffmanNode("000101", 'G');
                                addHuffmanNode("000110", 'Z');
                                addHuffmanNode("000111", 'U');
                                addHuffmanNode("001000", 'P');
                                addHuffmanNode("001001", 'B');
                                // depth 7
                                addHuffmanNode("0000110", 'H');
                                addHuffmanNode("0000111", '1');
                                addHuffmanNode("0001000", '2');
                                addHuffmanNode("0001001", '.');
                                // depth 8
                                addHuffmanNode("00000011", '5');
                                addHuffmanNode("00000100", '6');
                                addHuffmanNode("00000101", '-');
                                addHuffmanNode("00000110", '7');
                                addHuffmanNode("00000111", '3');
                                addHuffmanNode("00001000", '8');
                                addHuffmanNode("00001001", '9');
                                addHuffmanNode("00001010", '0');
                                addHuffmanNode("00001011", '4');
                                // depth 9
                                addHuffmanNode("000000010", 'F');
                                addHuffmanNode("000000011",',');
                                addHuffmanNode("000000100", '(');
                                addHuffmanNode("000000101", ')');
                                // depth 10
                                addHuffmanNode("0000000011", '*');
                                // depth 11
                                addHuffmanNode("00000000011", 'Y');
                                addHuffmanNode("00000000100", '"');
                                addHuffmanNode("00000000101", (char) 0x06); // non-print4
                                // depth 12
                                addHuffmanNode("000000000011", 'W');
                                addHuffmanNode("000000000100", 'X');
                                addHuffmanNode("000000000101", (char) 0x05); //non-print some shield code
                                // depth 13
                                addHuffmanNode("0000000000100", '&');
                                addHuffmanNode("0000000000101", (char) 0x1f); //non-print2
                                // depth 14
                                addHuffmanNode("00000000000011", 'Q');
                                addHuffmanNode("00000000000100", 'Š');
                                addHuffmanNode("00000000000101", '\''); // mdr16 says 0x8a
                                addHuffmanNode("00000000000110", 'Ë');
                                addHuffmanNode("00000000000111", '/');
                                // depth 15
                                addHuffmanNode("000000000000100", 'Æ');
                                addHuffmanNode("000000000000101", 'È');
                                // depth 16
                                addHuffmanNode("0000000000000101", (char) 0x04); // non-print3
                                addHuffmanNode("0000000000000110", '!');
                                addHuffmanNode("0000000000000111", (char) 0x9e); //Ž
                                // depth 17
                                addHuffmanNode("00000000000000110",'+');
                                addHuffmanNode("00000000000000111", '–'); // different to minus mdr16: 0x96
                                addHuffmanNode("00000000000001000", 'Á'); //Á
                                addHuffmanNode("00000000000001001", 'Ü');
                                // depth 18
                                addHuffmanNode("000000000000000110", '_');
                                addHuffmanNode("000000000000000111", '{');
                                addHuffmanNode("000000000000001000", '“'); // mdr16: 0x93
                                addHuffmanNode("000000000000001001", 'É');
                                addHuffmanNode("000000000000001010", 'Ð');
                                addHuffmanNode("000000000000001011", 'Ö');
                                // depth 19
                                addHuffmanNode("0000000000000000011", '?');
                                addHuffmanNode("0000000000000000100", '`'); // mdr16: 0x60
                                addHuffmanNode("0000000000000000101", '„'); // mdr16: 0x84
                                addHuffmanNode("0000000000000000110", 'ž'); // mdr16: 0x8e
                                addHuffmanNode("0000000000000000111", '’'); // mdr16: 0x92
                                addHuffmanNode("0000000000000001000", 'Ä');
                                addHuffmanNode("0000000000000001001", 'Ø');
                                addHuffmanNode("0000000000000001010", 'Ú');
                                addHuffmanNode("0000000000000001011", 'Û');
                                // depth 20
                                addHuffmanNode("00000000000000000000", '#'); // offset into MDR 30/31? MapSource displays "HWY "
                                addHuffmanNode("00000000000000000001", '%'); //
                                addHuffmanNode("00000000000000000010", ':');
                                addHuffmanNode("00000000000000000011", ';');
                                addHuffmanNode("00000000000000000100", (char) 0x8f);
                                addHuffmanNode("00000000000000000101", (char) 0xb8);

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Gerd Petermann <gpetermann_muenchen at hotmail.com>
Gesendet: Montag, 20. Dezember 2021 10:59
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev]       [mkgmap-svn]    Commit  r572:   MDR16   is      some    kind    of      codebook.

Hi Ticker,

OK, I see. It seems to work out for most of the delta values.
Deltas are 6,9,6,4,3,2,5,2,3,3,1,4,9,4

I'll try to find out if I can modify the tree so that it matches all numbers. Probably sometimes I found too short codes.
Good finding!

Gerd

________________________________________
Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Ticker Berkin <rwb-mkgmap at jagit.co.uk>
Gesendet: Montag, 20. Dezember 2021 10:38
An: Development list for mkgmap
Betreff: Re: [mkgmap-dev]       [mkgmap-svn]    Commit  r572:   MDR16   is      some    kind    of      codebook.

Hi Gerd

Are you OK with the idea of the letters at any level being to the
right. Then the letters at this level take decreasing values. When
exhausted, the next lower slot will be the start of the next level, so
subtract 1 to find it and append '1' to the bit-string to get the
starting position for the next level.

in the test map there is, say:

000002cf | 000019 | 11                      | struct level: 17
000002d0 | 00001a | 15 50 00 00             | struct for 17
000002d4 | 00001e | 10                      | struct level: 16
000002d5 | 00001f | 19 80 00 00             | struct for 16
000002d9 | 000023 | 0f                      | struct level: 15
000002da | 000024 | 1c c0 00 00             | struct for 15

The differences between the first byte after the level indicator ie 15,
19 & 1c) give 4 and 3, which are the number of letters at level 17 and
level 16

Ticker

On Mon, 2021-12-20 at 09:18 +0000, Gerd Petermann wrote:
> Hi Ticker,
> please explain. What counters do you see? What do they mean?
>
> Gerd
>
> ________________________________________
> Von: mkgmap-dev <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von
> Ticker Berkin <rwb-mkgmap at jagit.co.uk>
> Gesendet: Montag, 20. Dezember 2021 09:49
> An: Development list for mkgmap
> Betreff: Re: [mkgmap-dev]       [mkgmap-svn]    Commit  r572:   MDR16
> is      some    kind    of      codebook.
>
> Hi Gerd
>
> The tree is arranged so that letters at any level always have the
> highest values, ie come in from the right, and there are no gaps so no
> need for bit-flags. All it needs is the count of letters at each level
> to determine the tree.
>
> For levels 7 to 18 this is consistent and the count can be determined
> from the first byte in the "struct for {level}".
>
> Levels 19 and 20 are slightly out, but I think you found some
> strangeness here, including something indicate using Mdr3x data.
>
> Level 6 count might be mixed into the following
>
> I haven't been able to work out levels 1-5 yet, but somewhere would
> hope to find counts 0,0,1,7,9 maybe cumulative, maybe backwards, maybe
> without the first 2 values, maybe starting from the cumulative level 6
> value.
>
> Ticker
>
>
> On Sun, 2021-12-19 at 21:12 +0000, Gerd Petermann wrote:
> > 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
> >
> >
> > _______________________________________________
> > 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
>
>
> _______________________________________________
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