As I noted yesterday, part of the license that DVD makers have to sign is <a href="As I noted yesterday, part of the license that DVD makers have to sign is available on the DVD Copy Control Association (DVD-CCA) website. It’s 48 pages of dense technolegalese, consisting mostly of a list of things that DVD players aren’t allowed to do. On reading it, three things jumped out at me.
First, DVD region coding, the mechanism designed to stop DVDs bought in one part of the world from being played in another part, is the subject of much more regulatory effort than I expected. For example, there are special robustness requirements for region coding. (In the weird Orwellian language of DRM vendors, “robustness” is a code word denoting the use of deliberately complex, nonmodular designs so as to resist diagnosis, analysis, and repair.)
Second, it seems to be impossible to build a software DVD player that complies with the requirements. According to section 6.2.4.2 (page A-20),
Specificially, [software] implementations shall include all of the [required anti-reverse-engineering characteristics] which shall be implemented in a way that it is reasonably certain they: cannot be defeated or circumvented using widely accessible tools such as but not limited to debuggers, decompilers, and similar Software development products; and can only with difficulty be defeated or circumvented using professional computer engineering equipment such as … logic analyzers …
To comply with this, one would somehow have to write a piece of software whose data and algorithms absolutely cannot be determined by a person using a debugger or decompiler. We can be “reasonably certain” that any program written today can be understood using these tools. (It seems reasonable to read “cannot” as requiring absolute impenetrability, given that the next clause says “only with difficulty”.)
Third, the document bans DVD players from taking a movie that is encoded on a DVD at one level of resolution and outputting that movie on an analog output at a higher level of resolution. (Section 6.2.1.1 (2), page A-11) This ban holds even if the DVD publisher wants to allow a higher-resolution output. I couldn’t figure out what the purpose of this restriction might be. Maybe the document’s authors just got carried away after writing pages and pages of text limiting the functionality of DVD players.