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The Intel-developed technology is called High-bandwidth Digital Content Protection (HDCP) and aims to prevent copying of digital audio and video content as it travels across a variety of display connectors, even if such copying is not in violation of fair use laws.
Among the connectors supported by the technology are the Mini DisplayPort found on Apple's latest MacBook, MacBook Pro, and MacBook Air, in addition to others such as Digital Visual Interface (DVI), High-Definition Multimedia Interface (HDMI), Gigabit Video Interface (GVIF), and Unified Display Interface (UDI).
ArsTechnica reports that Apple has apparently acquired a license for the technology and is now using it across its DisplayPort-enabled MacBook lines to to prevent transmission of purchased iTunes content to devices that don't include support for HDCP.
"When my friend John, a high school teacher, attempted to play Hellboy 2 on his classroom's projector with a new aluminum MacBook over lunch, he was denied by the error you see [below]," writes Ars' David Chartier. "John's using a Mini DisplayPort-to-VGA adapter, plugged into a Sanyo projector that is part of his room's Promethean system."
The report adds that only a portion of Tunes Store video content is presently HDCP-aware, and in each case the protected files are wrapped in either version 2 or 3 of Apple's FairPlay digital rights management software.
Apple has said that it plans to adopt Mini DisplayPort across its entire product line, meaning that all future Macs from the Cupertino-based company are likely to include the same restrictions experienced by users of its latest notebooks.
iTunes denies playback of Hellboy 2 on a Sanyo projector | Source: ArsTechnica
As a licensed adopter of HDCP, Apple agrees to pay an annual fee and abide by the conditions set forth in Inte's HDCP License Agreement [PDF].
For example, the terms stipulate that high-definition digital video sources must not transmit protected content to non-HDCP-compliant receivers, as described above, and DVD-Audio content must be restricted to CD-audio quality or less when played back over non-HDCP-digital audio outputs.
Hardware vendors are also barred from allowing their devices to make copies of content, and must design their products in ways that "effectively frustrate attempts to defeat the content protection requirements." As such, the technology sometimes causes handshaking problems with older high-definition displays, which may explain the intermittent connection problems experienced by some other Unibody MacBook and MacBook Pro adopters.