Correction
Dear Gary: In Issue 64, Bob Perry replied to Don Shannon’s letter about IEEE 1394 versus DVI. In that reply, he stated that DVI is not recordable—which is not true. There is nothing preventing a DVI recorder from being built. Silicon Image, Genesis Microchip, and Texas Instruments are at least three manufacturers that make TMDS decoding chips that could be used to build a DVI input on, for example, a DVD recorder, like the one WSR reviewed in that issue. I imagine that Bob would probably respond that DVI’s (and HDMI’s) HDCP encryption would prevent recording. For material protected by HDCP, that’s true, but that’s also true for IEEE 1394 material protected by its equivalent 5C encryption. Pretending that same issue doesn't exist for IEEE 1394 will only prevent consumers from having their voices heard until it is too late.
Jeff Irwin
mailto:jirwin@rescomp.stanford.edu
Mitsubishi’s Bob Perry Comments:
With regard to Mr. Irwin’s comments, it is technically possible but practically unreasonable, to record the TMDS signal that is carried by the DVI connection. To record such a broadband (almost two gigabits per second) signal requires professional broadband recording technology that today sells for about $100,000. No DVD recording interface is capable of such recording data rate. If one wanted to compress the signal for recording, you would use a MPEG-2 type encoder ($80,000) and would end up with a MPEG-2 bitstream on.IEEE1394. With regard to DVI, the CE industry is rapidly moving to set a new form of DVI, known as HDMI, which is DVI with digital audio built into the connector and includes HDCP. The license agreement for HDCP, which is public, prohibits connecting an HDCP interface on a recording device. Therefore, the HDMI connector cannot be installed on a recorder. Some interpretations of the license indicate it would violate the license if you installed a HDCP enabled connector on a television with an integrated HD digital recorder. There is no question that the 5C encoding rules allow certain, specified content to be encoded as Copy Never, or Copy Once. This is the type of content that is currently not recordable and does not take away something that the consumer enjoys today, or expects to enjoy. DVI is quite different—from a practical standpoint, and specifically with regard to HDCP, it is unrecordable. In my article, I attempted to focus on what is reasonable and rational. I believe with an unlimited budget and resources, anything is possible—but quite unlikely. Thanks for reading and taking the time to respond.
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