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Updated post about U-Media AudioMate (Allnet Allsound).

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Markus Birth 2016-12-27 13:36:27 +01:00
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title: AudioMate Firmware title: AudioMate Firmware
layout: default layout: default
created: 2009-01-26 00:47:15 +0100 created: 2009-01-26 00:47:15 +0100
updated: 2009-06-26 23:59:11 +0200 updated: 2016-02-01 17:42:11 +0100
toc: false toc: false
tags: tags:
- know-how - know-how
@ -74,3 +74,23 @@ Well, there still is the way of having lots of `.m3u` playlists with links to yo
I still have to find out how the firmware gets checked for validity - because without knowing it, the firmware I still have to find out how the firmware gets checked for validity - because without knowing it, the firmware
containing my custom logo gets rejected. Seems like they didn't use a common checksum (CRC16 or CRC32) - or I didn't containing my custom logo gets rejected. Seems like they didn't use a common checksum (CRC16 or CRC32) - or I didn't
find the correct range of where the checksum gets calculated. find the correct range of where the checksum gets calculated.
Checksum
========
A user called "tidy" has found out what the header bytes are meaning and how checksum is compiled:
> bytes 0-3: file magic `UMDA`
> byte 4: Platform *
> byte 5+7: Customer * * (whatever that means its extracted from decompiling the header parse code)
> byte 6: Model *
> byte 8-10: Version number
> byte 11-12: build number (little endian)
> byte 13: flags seem to have impact on the update process but I'm not sure in which function
> byte 14-15: checksum
> The checksum is calculated by interpreting the file as a little endian int16 stream, adding up its
> values, truncating the 16LSBs after every addition and calculating the value that is missing to
> sum up to 0x10000. I.e. if one calculates the checksum as described over the whole file including
> the calculated checksum the result has to be zero.