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I'm trying to reverse a qdsp6 modem file but I'm stuck with the (probably) compressed segments.

There is also a third compressed segment which simply uses zlib but the other two are not recognized by binwalk. I also compared the header to the compressed segments of a Pixel 2 modem firmware. Pixel 2 uses q6zip and delta (as mentioned here and maybe here), but not even the first bytes of those segments match.

Also searched for both segments offsets in the binary, but they can't be found as immediate. So simply looking for them to find the decompression function isn't possible.

The entropy of them looks like that:

modem.b26

enter image description here

Binwalk mentions parity information, but it is in the area of high entropy. So maybe it is a false positive?:

> binwalk modem.b26

DECIMAL       HEXADECIMAL     DESCRIPTION
--------------------------------------------------------------------------------
25953729      0x18C05C1       MPEG transport stream data
29114525      0x1BC409D       PARity archive data - file number 16432

The first few bytes are:

> xxd -c 16 modem.b26  | head -n 3
00000000: 3c9b 9ed4 bb7b 281c 050f 8a9c d875 4130  <....{(......uA0
00000010: 801d 8619 2c17 8028 2ea1 bbee db57 0160  ....,..(.....W.`
00000020: e17c 846c 2a18 14c8 2db0 20ae f952 0041  .|.l*...-. ..R.A

modem.b28

enter image description here

  • Binwalk returns nothing.

The first few bytes are:

> xxd -c 16 modem.b28  | head -n 3
00000000: 1200 0000 4c00 59ce 3c11 59ce 3c22 59ce  ....L.Y.<.Y.<"Y.
00000010: 3c33 59ce 3c44 59ce 3855 59ce f465 59ce  <3Y.<DY.8UY..eY.
00000020: bc76 59ce bc87 59ce bc98 59ce bca9 59ce  .vY...Y...Y...Y.

Do you have any idea how to proceed to decompress those segments?

1 Answer 1

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Possible solution for unpacking could be here. But haven't tested them yet. https://github.com/tewilove/q6dlpager

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  • Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.
    – NirIzr
    Dec 9, 2021 at 12:54
  • Will add them once I managed to decompress those segments myself. Just wanted to not forget about it and give others a hint as soon as possible.
    – ASDdoogle
    Dec 9, 2021 at 17:40

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