News and Reviews....
The Dreaded - Image Constraint Token .......... April 2008
By Robert Lieto
Image Constraint Token (ICT) is not a term that I would expect our customers to be familiar with, but one that we are constantly weighting in on and monitoring. It is less a weight in new system designs, depending on how elaborate your design, as it is in ones that are 4 to 7 years or more old because they probably use Component type wiring in their video signal feeds and paths.
To fully understand the ICT impact we need to know the common types of video signals used for ICT impacts the video signal directly. The least complex of all video signals is the composite video signal also called CVBS (Composite Video Blanking and Sync), or Composite Video Baseband Signal. It combines all elements or components of a Video signal onto one wire. The wire is in a coaxial arrangement with a center conductor for signal and shield to ground, and delivered typically through a RCA connector. It has some downside or reserve related to the mixing or intermodulation of the components of the signal. To advert the problems associated with the combining and un-combining of the signal within the composite realm, we would need to send the components of the Video signal on separate wires so they don't interfere with each other, or the need to be processed in any way. The components of the video signal can be sent on as little as two (2) wires, plus ground to keep the integrity of the signals without having to mix or inter-modulate. Video signals made up of components are called Component Video Signals.
Component video signals are analog signals and known in name as S-Video, RGB and YPbPr, among others, which comprise the two or more separate wires needed. Component video outputs are capable of providing signals such as 480i, 480p, 540p, 720p, and 1080i and 1080p. Although many TVs do not support 1080p through the component video input circuitry.
ICT (Image Constraint Token) is a limit on the highest resolutions allowed or passed out of the component video signal outputs of a source device, and are set in place on a "one by one" basis in the High Definition programs of the device, be it a Blu-Ray Disc, Satellite or Cable box, TIVO..... and others. The reason is to prevent a High Resolution Analog copy of material crossing over onto a Disc form in the Digital Domain.
A first generation copy, of a High Resolution analog signal, say in the 720P range, onto a HD-DVD recording machine will produce a copy of better then standard DVD quality. Not Bad. The movie studios want to limit that quality by means of the ICT, and the limit on the analog component outputs to 480 lines. It will not make much difference with conventional DVDs, for the maximum native resolution obtainable is about the same, but to copy onto the new high resolution discs will get very good results. And so, to the ICT advocates, any output on a source machine but the Digital DVI (Digital Video Interface) or HDMI (High Definition Media Interface) will deliver picture at a much lower grade. Thereby controlling the Highest resolution program to only the Digital Domain which will not allow a copy or output of the digital signal. A subsequent question arises of legitimate DVD players in market and existing now, that can up-convert to the higher formats and process out of their Component Video Outputs, will they be allowed to remain in the market place, or in turn set off another battle in the courts as to their rights and worth to the consumer, set against cost within, and to, the market in general.
The DVI or HDMI are the newest edition to the Video signal realm, as mentioned above. The DVI or HDMI interface send digital signals on separate wires and include the audio channels as well, all in one connector. The two cable formats control the digital signals and use the Image Constraint Token as the wedge to prod the consumer to upgrade to the Digital Domain as dictated by the new Digital signal form of DVI and HDMI. You see in products that use the DVI or HDMI connector the HD Digital source manufacturer can control the Digital signal and not allow it to be copied in digital form by requesting a sort of hand shake before the signal can be passed. It is the copy protection of an exact digital copy related to the highest resolutions in HDTV that are at risk, if you listen to the pundits. They have a right to protect an exact copy and digital provides that kind of copy, it is the nature of the beast. But are we be subjected by the advancements in technical process itself. And, what if in years to come, they (the powers at be) decide to eliminate all the analog outputs, with just DVI and HDMI existing, the system hookup would be easier but very inflexible. The job of the A/V integrator increased 5 fold in complexity and know-how separates the men from the boys.
The latest report is that the ICT will probably not be used until at least 2010, which means that Blu-Ray disc releases will be feeding the component video outputs and subsequent inputs of all early generation HDTVs with true high-def signals without invoking..... The Dreaded Image Constraint Token.
Comment ..... We are in a time when the Analog program materials and Digital Domains are starting to mesh. Once the combinatiion is complete, will the world of Digital Audio and Video develop to become one closed loop with the source manufacturers and software programmers, the gate keepers, or maybe we will grow to have, all materials ever written, spoken, filmed, sung, televised, and recorded... at our fingertips, in an instant, at any particular time, for a monthly charge, thereby eliminating the need for copy or storage. Very Possible. For now, we feel the intent of limiting quality to the consumer is debatable, it stymies creative talents, inhibits innovation and is fundamentally wrong. It embarks down the path to a deepening in customer dissatisfaction based on limits and will ultimately slow down the very market it needs to support. It sheds a light once again on the personal right to use issue on the products purchased for convenience, enjoyment or service, for your person, family or friends. Should the DVI and HDMI interface be controlled and not allowed to overtake and become the standard interface? More to come on this subject.
