The good news is that there is a fully-compatible HD FireWire configuration called “DTV Link.” Because FireWire connections are “selfconfiguring” and “self-recognizing,” you can connect a FireWire device to a DTV Link television, and the set will sense the new device and configure for it. The DTV Link sets will also display on-screen controls for the new device, such as the FAST FORWARD, PLAY, and RECORD controls for a DVR. In some cases interoperability is enhanced by device-todevice control protocols such as AVC (Audio Video Control) and HAVi (Home Audio Video interoperability). One word of caution: A number of FireWire-equipped 2004 models lacked the software for full “DTV Link” functionality. Non-DTV Link sets may be unusable as hubs, or incompatible with some current or future HD recording devices.
If you want to connect a FireWire device to a DTV Link HDTV, plug in the appropriate FireWire cable between the display and the device. Both HD-video and digital-audio signals pass through FireWire, so only one cable is needed to connect a pair of devices, but it is also possible to configure “daisy chains” that link up to 64 devices! The maximum length of each FireWire cable is 4.5 meters, but this could soon change to a whopping 70 meters. Cable companies are required to provide FireWire connections upon customer request for rented HD boxes. As noted, neither DISHNetwork nor DirecTV offers this connection, making it impossible to archive any satellite HD content on removable media.
There are three types of source-component-to-HD-display connections today, each with different characteristics and limitations.
The first is component video, which is an analog form of HDTV. It requires three connector cables that run between the source and the display. We expect component video will be phased out as an HD connection, owing to complexity of its structure (three wires instead of one), the relatively limited length of cable runs possible with it, and its inability to support digital copy protection. Toshiba has, for example, announced that its upcoming HD DVD disc player will deliver HD signals via digital (HDMI and FireWire) outputs only, while component-video outputs will be limited to down-rez’d, standard-definition versions of HD content. Next, we have two digital connection formats: DVI (Digital Visual Interface) and HDMI (High-Definition Multimedia Interface). Both are copy-protected interfaces (using a protection scheme called HDCP) that use decompressed HD-program streams. (See page 94 for an extensive discussion of each.)
DVI carries video signals only, while HDMI carries both digital audio and video, which may make HDMI the interface of choice. HDMI also enjoys an edge in terms of maximum cable length; DVI interfaces support maximum runs of 9.6 meters (about 30 feet), while the more robust HDMI allows cable runs of up to 75 feet.
Either format can transmit HD signals over even longer distances via powered repeaters (also called active cables). FireWire can also be extended by use of an active cable or repeater.N