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Tuesday, October 20th, 2009

Reverse Engineering the param.cfg file of Cowon's iAudio 7 player

Categories: [ IT ]

While I'm eating at work, I like to listen to the same podcast I was listening while commuting. But I don't want to search manually which file I was listening to, and at what point in the podcast I shut the player down. Since this information is probably in the player's system files somewhere, I just had to hack a bit and see if I could extract it.

The relevant file is system/param.cfg. At offset 0x0F, one can read a big-endian 16-bit number which is the offset in seconds from the beginning of the file where playing was stopped. That part was easy.

Now for the actual file. At offset 0x879, one can read a big-endian 32-bit number which is the first File Allocation Table entry of the file. And somehow, this wasn't difficult to guess, I probably would have designed it that way myself… Thankfully, the Mtools package in GNU offers a tool called mshowfat which takes a DOS path as an argument and returns the FAT range occupied by that file.

And Bob's your uncle.

[ Posted on October 20th, 2009 at 12:23 | no comment | ]