Analog reconversion and copy quality

All copy-protection schemes have at least one prominent hole. At some point, they have to deliver you something. A music player has to play music, a document viewer has to show you a document, and so forth.

There's nothing at all stopping you from recording the sound that comes out of the headphones, or taking a picture of a document on a screen (and in the Trusted Computing nightmare scenario of the disappearing order, that might be a very good idea).

Of course, the usual objection is that you've lost information in the process. You've lost sound quality in the case of music. In the case of a document, you're just seeing text on the screen, not the underlying markup or structure.

Well yes, but ... if all you can do with a piece of music is play it on your headphones, and you record the analog signal going to the headphones (or even coming out of the headphones), then you have copied all the information needed to listen to the music with the quality those headphones give. Which is all you had in the first place.

Similarly, if you capture the images on the screen as you view a document, then you can go back and re-read the document any time you want. With optical character recognition, you could even reconstruct the text with fair accuracy. The process in general is called analog reconversion.

If all you are granted is the ability to view images or listen to sound, then you have already lost information. Recording the analog signal results in further loss, but as playback and recording equipment gets better and better, the loss becomes less and less perceptible. The ultimate limit here is human bandwidth, not computer bandwidth.

At the moment, recapturing the full glory of an HD DVD is beyond most people's capability. There are just too many bits going up on the screen and compressing would take too long. But grabbing enough to re-sell as a cheap pirated copy is clearly within many people's capability, and Moore's law will come into play sooner or later.

Attempts to plug this "analog hole" tend to be draconian, e.g., restricting the use of digital recording devices, and don't tend to get very far. Not that that will keep people from trying.

Hypertext is an interesting counterexample. I could record my viewing of a web site, and probably even analyze the results and reconstruct the links I've followed. What I can't do, however, is know what's behind the links I didn't follow, or even where they point.