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Old 01-18-2011, 04:16 PM   #1
nekron
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Device: PRS650
Lightbulb Anyone knows how to fix the random "protected by DRM" message?

I recently started to examine porcus PRS650 dump in order to fix the problem many PRS350/650/950 owners expire sooner or later: When you are reading a DRM protected and the device turns off (not standy) and you power it on again and try to open your current ebook sometime you get "protected by DRM" message. If you switch back to the main screen of your reader and try to re-open the book again the message still displays. As a fix you can open a different book and return to your original reading afterwards, but however you will lose your latest reading position, all of your bookmarks and notes. So this is really annoying for me since I read my ebooks until the battery dies and I have to fully recharge the beast. At one time my battery went dead as the reader was in standby screen powering off and after recharing it the message appears. Oh well, so good' ol Nekron thought: Get that damn firmware and have a look at it (after I emailed Sony but I bet we will never see this fixed ...). So what I think is:

- the "procted by DRM" screen appears randomly (yesterday I tried to simulate the error by turning the device on and off, but got that DRM screen only once).
- often you get the DRM screen when you are on low battery and wait until it dies (e.g. if on low bat turn on the MP3 player on a endless loop. It will turn off in a while and next time for sure you power it on your current ebook will show that message if you where reading DRM protected content)
- since there is now way to reproduce the DRM screen in a safe way it looks like a randomly error
- your current book is cached somewhere on a non-public accessable partion (I did not yet manage to flash the usb over serial stuff) I found DEFSKing the .so and .xsb files
- after the linux rc script mounts a lot of stuff and loads kernel drivers the tinyhttp binary is started launching the PRS application (kbook)
- when tinyhttp exists a few lines of the startup bash script are execute to sync the filesystem and execute the poweroff command which turns of the reader

Conclusion so far:

- since the "procted by DRM" screen appears randomly a software bug for the kbook (tinyhttp) application seems unlikely to me
- your current ebook is cached, The javascript found in xsb and .so files show that some DRM parameter is cached, too
- when the device is turned off i/o operation to the flashdisk is sync'ed three times before it powers off

I am not sure, but might it be possible that the current books cache is corrupted when the device powers off in case of low battery or by manual turn off and that this happend, because of unwritten or incomplete written cache files? Since I havent yet seen the fiel system in action and do not know if there is a cache / database for your ebook, could this possibly the fault?

Any ideas or maybe someone (our Russian friends) fixed it?

Cheers,
Nek
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Old 01-19-2011, 09:23 AM   #2
elcreative
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nekron, a separate issue... try not to totally discharge the battery, this behaviour will shorten the life of lithium batteries which, not only don't need, but are actively harmed by full discharge/recharge cycles... this is from the battery manufacturers...
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