I wasn't aware of the troubles that the Engadget article mentioned. It figures that Sony would be then one to cause a widespread screw-up on DVD players.
http://www.engadget.com/2007/04/16/sony-copy-protection-taking-heat-again-now-dvds-wont-play/ said:
Many older (or less sophisticated) players simply skip these corrupted areas as unreadable and continue on. Computers -- and unfortunately, some newer players -- try to perform error correction on these areas and fail playback.
That makes sense.
Also, I didn't mean to be misleading in the thread title - I was really just curious about how the protection technology worked (without getting too technical and obviously without getting into proprietary details). From an academic standpoint, it's an interesting problem that's nearly a paradox - how do you put out a single stream of information that's supposed to be publicly readable on one set of widely available devices, but not on another set. It seems similar to saying you want to publish a dead-tree paper book that gets sold in regular bookstores that women can read but men can't.
Clearly crypto is one possible answer, and CSS was an attempt to do that. But CSS was circumvented a long time ago (for more than one reason, as I understand it), and new crypto could not be added to the huge set of existing machines. So new protection methods would seem to have to use something that's different from crypto.
From reading here it seems that the protections use a variety of things like bogus files, bogus file metadata (sizes, etc. I think), and structural protections (whatever they are). For the time being, lets leave aside the gnarly Sony stuff that does seem to break on stand-alone players. I'd guess that the vast majority of protections do not cause problems on the vast majority of players (otherwise Blockbuster would have been out of business a long time ago). Also, let's leave aside whatever AnyDVD does to undo these protections.
So to wrap up my long question with a long summary of the question: why do these protections confuse or cause problems on PCs but not standalones? I'm not trying to gain any 'insider' information or figure out how to write AnyDVD or say that there's not much complexity to what AnyDVD does. Believe me, I wouldn't understand it at that level - I'm more looking for the level of detail that 's given to a topic on the howitworks.com website (you know, picture-book level). And, of course, I have no *need* for this information, I'm just curious.
Maybe the answer is simply in the fact that PC's get hung up on error-correction. But I would have thought there would be more to it than that.