News Changes/ Component & IEEE 1394
Dear Gary: have two questions for you. First, I have been frequenting your site for several years now, especially regarding your fantastic news areas. But, for some time now, instead of daily news, the news is very infrequent. What happened? For years the news was daily. Now though, it is almost non-existent, at least when compared to previous years. Is this the way it will be from now on? Second, It has recently come to my attention, through newsgroups on the Internet, that IEEE 1394 is being considered the “connection of choice” for high quality video transmission. Component has always been considered the best for video transmission, especially by video professionals in Hollywood post production work. Is component still the interface of choice for high quality video? Is IEEE 1394 considered better?
Jim Buchanan
Managing Editor Perry Sun Comments: We have decided to scale back the scope of news coverage on our site, focusing predominantly on consumer electronics/home theatre-relevant developments. Our staff devotes time both to our print magazine and the Web site, and, with our recent, dramatic growth, it has become difficult to manage the Web site in its current form. We now provide online news coverage every other business day. In regards to your second issue, IEEE 1394 is a potential solution for digital connectivity between DTV set-top boxes, DTV sets, and digital recorders for DTV. The other digital interface under consideration is DVI (Digital Visual Interface). IEEE 1394 is supported by the Consumer Electronics Association, as well as consumer electronics manufacturers (Sony and Mitsubishi among others) and two studios (Sony Pictures and Warner Bros.). Both interfaces have their own copy protection protocols (DTCP or “5C” for IEEE 1394, and HDCP for DVI), but many studios favor DVI, because the HDCP standard has a more stringent conditional access approach to copy protection. In order words, the studios want the maximum protection possible from having digital broadcasts pirated, even if it means potentially restricting the consumer from recording off-the-air broadcast programs. For video professionals, the digital video interfaces used are SDI (Serial Digital Interface), and HD-SDI for high-definition applications, both of which support uncompressed component video. Video Technical Editor Greg Rogers Comments: The best video interface depends on what you need it to do, and who gets to choose. Component video interfaces can be analog or digital, RGB or YPbPr. We currently use analog component video interfaces to connect consumer video products such as DVD players and HDTV set-top boxes to displays. Professional video, used in broadcast and production facilities, uses digital YCbCr component video to interconnect products, such as cameras to digital tape recorders or video processors. Analog component video uses parallel interfaces—one cable for each component video signal, and up to two more cables for separate sync signals. Digital component video is typically transmitted over a serial digital interface (SDI). Digital component video data and equivalent sync information can be transmitted in a single SDI cable, but the serial data rates are extremely high. Standard-definition 10-bit SDI (SMPTE 259M) video is usually transmitted at a rate of 270 Mbps (megabits per second), and high-definition 10-bit HD-SDI (SMPTE 292M) video is about 1.5 Gbps (1500 Mbps). The cost of implementing HD-SDI video for consumer products is too high, and more importantly, no content protection exists for these standards. But for professional video applications, SDI and HD-SDI provide high quality, uncompressed component video. IEEE 1394, otherwise known as FireWire® by its inventor Apple Computer (Sony calls it i.LINK), is a general-purpose serial bus that has been adapted for transmitting compressed digital video. It currently has a maximum serial data rate of about 400 Mbps, although faster versions of the standard are being developed (up to 3.2 Gbps). But for now it is primarily being touted for transmitting MPEG compressed video between devices such as satellite receivers and consumer digital video recorders. The cable TV industry had also adopted 1394 for connecting set-top boxes to high-definition TVs. The key enabler for using IEEE 1394 is Digital Transmission Content Protection (DTCP), also known as “5C,” which refers to the companies that developed it. Just as we are going to press with this issue, a broad group of satellite and cable TV providers (including DirecTV® and EchoStar’s DISH Network®), consumer electronics manufacturers, and content providers, have agreed to use the Digital Visual Interface (DVI) standard for transmission from HDTV set-top boxes to displays, and high-bandwidth digital content protection (HDCP) for HDTV content. The DVI/HDCP standard uses four pairs of differential signals (digital RGB & clock) and has a maximum data rate of 4.95 Gbps, to deliver uncompressed high-definition video. We will have much more to say about the implications of this announcement in future issues. For more technical information read Alen Koebel’s article, “Digital Video Interfaces And Consumer Displays,” in Issue 47.
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