Rockbox mail archive
Subject: Re: Gmini Firmware question
From: Magnus Holmgren (lear_at_algonet.se)
Laurent Giroud wrote:
> The first missing point is figuring the compression algorithm. Gzip
> can't compress the firmware file by more than 2 or 3 percents which
> is a good indicator and there's a 'CCOD' chunk which might stand for
> "Compressed code" and one 32 bits field yields a value which is
> approx 2 times bigger than each firmware file and would be a very
> good candidate for the decompressed firmware size.
Just as a side note, but gzip not being able to compress it much doesn't
necessarily mean that the file was compressed to begin with. A simple
"encryption" can have that effect too (I saw it with a file that was
"decrypted" by doing something like <byte n> = <byte n> XOR <byte n-1>,
with a seed for byte -1).
Page was last modified "Jan 10 2012" The Rockbox Crew