IBM this week eliminated the Linux multimedia gap with the release of the T22 ThinkPad. Big Blue's latest offering is the first commercially available Linux computer with the ability to play back DVDs.There is no love lost between the communities of Open Source and the Motion Picture Association of America, especially since the MPAA hauled a Web site operator into court for merely linking to a few lines of code that bypassed the DVD location restriction features. The court decided that DVD's not-so-secret workings were protected by copyright.
Using existing Open Source solutions to provide DVD playback under Linux was out of the question for IBM. The challenge for Big Blue's mobile computing division was to create a solution that could preserve the copy protection essential to avoiding an MPAA lawsuit.
That challenge became the responsibility of Keith Frechette, the Linux development lead for IBM's Mobile Computing Options and Software Development division. "While I can say (those challenges are) 'interesting' now, several months ago I would have chosen a different word," wrote Frechette in a post to the linux-thinkpad mailing list.
IBM chose a new product from InterVideo, known for its WinDVD software for the Windows operating system, and bundled with many new computer systems. LinDVD offers many of the same features as its Windows counterpart, including movie and interactive DVD playback along with support for Video CDs (VCD) and MPEG files. Also included is a decoder for multi-channel Dolby Digital audio.
Getting the copy protection features working with Linux and LinDVD took considerable time. "For laptops, the primary mechanism for stopping DVD movie piracy over the S-Video port is to encode out-going video signal using Macrovision," said Frechette. First developed to thwart copying of videotapes, Macrovision is now the industry standard "digital rights management technology" to prevent the transfer of DVD contents to tape or hard drives.
Windows' video driver architecture offers developers a standard mechanism for enabling Macrovision; no such standard exists for Linux. Frechette's group worked with InterVideo to develop an interface that allows LinDVD to enable Macrovision's copy protection when it's needed. Pratchette considers IBM's work a start, not a standard, instead hoping that "perhaps the Linux community will define a standard interface for this, possibly taking advantage of some of the work that we did."
After tying all that together, it was time to figure out where to put the Macrovision control logic code. Windows places it in the video driver, which is a perfect location for a closed-source operating system. The video drivers behind X, however, are Open Sourced. While some users would love to take a crack at the Macrovision code, that simply wouldn't do for this project.
Frechette's solution was to drop the code into a binary-only kernel driver. "This provides adequate protection, but it does tie the Macrovision support to specific kernels," he admitted. Plans for future version of IBM's Linux ThinkPad DVD playback system might include placing the Macrovision code into a user-mode driver/daemon.
"I hope that our success helps to raise the bar just a little, that in the future DVD movie support on Linux will be commonplace, and that we can say to Windows users, DVD movie playback -- yeah, we've got that."
The IBM T22 ThinkPad features a base configuration that includes Caldera OpenLinux eDesktop 2.4, a 900Mhz Pentium III processor, 128MB RAM, 14.1" TFT active matrix display, and a 20GB hard drive -- and DVD support, of course. Manufacturer's suggested retail price is $3,499.
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