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Re: [libredwg] reed solomon

From: Till Heuschmann
Subject: Re: [libredwg] reed solomon
Date: Mon, 30 Aug 2010 18:49:05 +0200
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; de; rv: Gecko/20100711 Thunderbird/3.0.6

Hi Mike,

I'am working on the R2007 reader which for now just extracts the encoded data and ignores the rs parity bytes.
So I can provide you some data and give you some hints how to read it.
Attached is the rs data found at offset 0x80 in a .dwg file. The data is
0x3d8 bytes long and contains 3 blocks of rs data. One block contains 239 bytes of data and 16 parity bytes.
The blocks are interleaved with a factor of 3.

The given data starts like this:
B3 01 68 D2 58 01 70 67 51 9E 00 7F 26 01 01 80 CD F0 68 A5

...and so the first rs encoded block starts with:
B3  D2  70  9E  26  80

the rest of the data (0x3d8 - (3 * 0xFF) = 0xDB) are padded and not rs encoded.

If you need some more data feel free to ask. I will push a first version of the reader in the next weeks.


Am 30.08.2010 08:02, schrieb address@hidden:
hi all,
I have started to research into this reed solomon stuff, it does not
look that hard.–Solomon_error_correction
also MIT OCW :

can you please provide me with a block of pure data that is in RS
format and the encoding parameters. I am going to work on a decoder.


Attachment: rsdata.dat
Description: Binary data

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