Some updates.-----------------
OK, that was kind of right. Part 5 has a 4 byte footer.
But whole file have like 4 byte counter after every 24 bytes. From the beginning we can see
6 bytes where last two are 65536 byte counters - 02 00 00 04 00 00 which 8-byte checksum
is next - FA. After that is starting data counter 18 00 00 00 and it continues 18 00 18 00...
18 00 30 00... 18 00 48 00. But not like this to the end, after every 65536 bytes is that
6 byte counter part.
After every data part is 8-bit checksum from previous data and counter, usually from 28 bytes.
So, counters are zeroed out and file is beginning:
02 00 00 04 00 00 --- counted 00 bytes
18 00 00 00 --- 18 - count 24 bytes
next is
18 00 18 00
| |---------24 bytes is counted
|---------------count 24 bytes
next is
18 00 30 00
| |---------48 bytes is counted
|---------------count 24 bytes
...
and so on until counter fills up
...
18 FF D8 00
10 FF F0 00
| |---------65520 bytes is counted
|---------------count 16 bytes
now counter is over FF FF and comes
02 00 00 04 00 01
|----first 65536 bytes is counted
and counter starts again
18 00 00 00
| |---------0 bytes is counted
|---------------count 24 bytes
...
and so on when last 2 are
18 F8 58 00
| |---------63576 bytes is counted
|---------------count 24 bytes
07 F8 70 00
| |---------63600 bytes is counted
|---------------count 7 bytes
and last bytes of file are
00 00 00 01 FF
|
|---------------count 0 bytes - so it is the end of file
This is 4 byte footer which 8-bit checksum is FF. Maybe 01 is marking "end of file 1".
Now if we remove all counter parts and checksums, we get clean file and after decompressing
it the Adler32 is matching with 95 88 CE 76 at the end in original Part_5.hex in last data packet
before checksum.
Now if I remove all of the counter parts I get clean file and after decompressing it
I get Adler32 from the end of data - 95 88 CE 76
I was hoping to see there something interesting, like logo in SDG1000 file but ... boring...
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decompressed second part from part 5 of sds2k_V100R02B01D01P38R07_fvA1606060606M160516.ADS