RFH: ARM/Thumb Programing

Feb 01, 2007 6 Replies
R

G'Day, I have a stand-alone Liteon 5115 DVD recorder that I purchased to transfer my VHS tape collection to DVD before VHS hardware becomes obsolete. Unfortunately, many tapes cannot be transferred as the recorder displays "Protected Content" (i.e. Macrovision) and recording will not proceed. Legally, under our fair-use law, we are allowed to make a personal copy.



Therefore, I did a hex-dump of the firmware (a copy of the firmware is available at:

formatting link
) and discovered the following:



At 0x2DB9F1 a reference to Mediatek (Manufacturer of DVD Recorder chipsets who have also signed an agreement with ARM).



At 0x361DC a reference to ARM



At 0x2D78DD the following hex string: 55 53 00 00 00 00 00 01 00 00 00



00 (This is the same string that a Liteon 5005 recorder uses for its Region Code and Copy Protection switches which can be modified to 55
53 00 00 00 00 00 00 00 00 00 01 to make that recorder Region Free and Copy Protection disabled.

Please advise, in layman terms if possible, the steps and tools required to fully reverse engineer (disassemble/decompile/debug) this firmware to discover checksums, etc. TIA!



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L

Legally, under the DMCA, all of us living in America cannot disclose to you a method of defeating copy protection, regardless of your fair- use laws (and for that matter, regardless of ours). This works both ways, too - if you work out how to do it, and let America know, you can be arrested if you visit here. Look up the case of Dmitry Sklyarov vs. Adobe. Remember that every time you buy an MPAA movie or RIAA audio recording, you are subsidizing this theft of freedom.

This can't be made layman-friendly. Even if the structure you have found is in fact what you think it is [and the chances are very good that it is a mere coincidental run of bytes], substantial work will be necessary to locate the checksum routine and patch it out. A very useful time-saving tool for this sort of work is Ida Pro, but it is not a layman process.

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L

By the way, the best way to get around your specific problem is to put a Macrovision scrubber between the VHS deck and the DVD recorder. Of course, these devices are not manufacturable legally (since Macrovision holds patents on most or all of the technologies required to build such a scrubber). However, they are readily available.

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M

I am not sure about your problem - but I can advise you that there are such things as "video clarifiers" (check Ebay) that take care of this problem.

-Mike

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R

Thanks Mike, I know but I would prefer the firmware route.

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L

If the structure you're looking at is what you think it is, it will doubtless ONLY disable Macrovision on the video OUT of the device.

Detecting Macrovision in an incoming analog video stream is a different task and you'll likely have to patch actual code to remove it.

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R

Thanks larwe, you might be correct, however, in Liteon's previous model (5005) modifying that string disables MV completely (changed to

55 53 00 00 00 00 00 00 00 00 00 01) without hav> >
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