Published: TV Technology Magazine

Issue:  27 July 1998



Gennum Eases DTV Transition Woes



by Joe Fedele



BURLINGTON, Ontario

  Engineers anxious over utilizing an analog infrastructure for digital distribution may have found a 

potential solution. 



  Gennum Corp., a Canadian-based IC chip manufacturer for professional video products, has developed 

several new chipsets that will allow manufacturers to build equipment that can route and distribute high-

speed data over analog and digital coaxial cable in a more robust manner.



  Touting it as "the video industry's first  integrated HDTV cable equalizer and cable driver for 1.485 

Gbps 

HDTV applications," Gennum has introduced the HD-LINX, a line of serial digital cable equalizers and 

cable driver chips. The chips, according to Gennum, enable manufacturers to produce equipment that 

utilizes an existing coaxial infrastructure for full bandwidth, 1.485 Gbps DTV routing and distribution.  

  This will allow broadcasters to use their existing coaxial infrastructure for full bandwidth 1.485 Gbps 

DTV routing and distribution.



  Without this kind of cable equalization, some broadcasters would be faced with replacing part, if not 

most, 

of their existing infrastructure with more expensive cabling.  



  Much of the older cabling used in some facilities is often limited in its bandwidth-handling capabilities. 

This is primarily due to fact that it was simply not designed to carry the 1.485 Gbps payload specified in 

the 

SMPTE 292M standard over long distances (see sidebars). As broadcast stations begin to transition to 

DTV, some engineers will be faced with delivering 1.485 Gbps data throughout their facility. Those 

requirements may translate into the replacement of a sizable portion of a facility's infrastructure. 

  "Uncompressed, 1.485 Gbps datarates put a tremendous strain on a plant's infrastructure," said Paul 

Scaglione, director of engineering for the Telemundo Network in Miami. "Inferior grades of coax cable 

simply will not meet the challenges imposed by high very speed data rates like those specified in SMPTE 

292M." 



  "Through the use of products made with Gennum's IC chipset line, broadcasters would not have to 

upgrade 

their entire facility with higher-quality cable or expensive fiber optics," added Eric Fankhauser, manager 

marketing of video and broadcast products for Gennum.



  According to Gennum, by "future proofing" a facility, broadcasters would be able to use standard 

coaxial 

cable and higher-quality serial digital interface (SDI) cabling as the interconnect of choice for 

uncompressed HDTV digital video's bandwidth-intensive applications.





CABLE SPECIFICS



  The Gennum model GS1504 cable equalizers and GS1508 cable drivers are specified to achieve 

transmission distances of more than 150 meters (492 feet) with high-quality cable. This yields about a 

27-

percent improvement in transmission capabilities at 1.485 Gbps.



  Earlier this year, Gennum introduced several other chipsets that enable 540 Mbps serial digital routing 

and 

distribution. A 540 Mbps standard is desirable in new studio applications where a higher-speed 

infrastructure is needed to support applications such as the interconnecting of 4:2:2 sampled 525- or 625-

line progressively scanned video formats. Other applications for the 540 Mbps distribution include a 

higher 

payload link for Serial Data Transport Interface (SDTI) packetized interconnect, which includes lossless 

compressed HDTV signals, twice real-time transfers of 4:2:2 uncompressed video, and single link 

4:4:4:4 

transfers for high-end compositing and effects applications. 



  According to Gennum's specifications, the utilization of a 540 Mbps SDI link, rather than a standard 

270 

Mbps one, will allow all these bandwidth-intensive applications to be facilitated without the need of new 

high-grade coax or fiber-optic cabling. Gennum has also made its line of equipment to be fully backward 

compatible with older equipment and will operate at data rates of  143 Mbps to 540 Mbps. The company 

is 

offering several other lines of 540 Mbps chipsets that include serial digital crosspoint switches and 

reclockers as well as cable equalizers and drivers.



  The inclusion of 540 Mbps distribution capabilities hinges on the availability of higher-speed routers, 

distribution amplifiers and other products which are currently not available, the company said. A number 

of 

manufacturers are currently developing such 540 Mbps terminal gear. But until a wide variety of high-

speed 

equipment is readily available, some of these capabilities are reserved for future use, Gennum believes.

  Several manufacturers have already begun new designs to replace older 270 Mpbs and 360 Mbps 

products 

and produce equipment that can handle HDTV data rates. Equipment makers likely to use Gennum's new 

chipsets include Tektronix/GVG, Miranda, Matsushita, Philips BTS, Pro-Bel and Leitch, the company 

said.