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HDTV interface spec sparks product rollouts

Posted: 01 Jun 2007 ?? ?Print Version ?Bookmark and Share

Keywords:3G SDI products chipset? 3G interface standard? FPGA for broadcasting equipment?

Chipmakers are rushing out competitive solutions for the emerging third-generation Serial Digital Interface (3G-SDI) standard.

Late in 2006, the Society of Motion Picture and Television Engineers approved the new 3Gbps SDI standard as SMPTE-424M. The third-generation serial link promises to double the transport rates of existing HDTV transmissions in the high-end studio environment. It is also said to boost the overall quality of broadcast transmissions in the network.

Hollywood interest
Major production studios and TV networks are jumping on the 3G-SDI bandwagon, presenting welcome opportunities for semiconductor makers in the midst of what many characterize as a chip industry lull. Suppliers of rival ASICs, ASSPs and FPGAs are vying for early sockets in high-end broadcasting equipment, though not all will benefit from the boom.

One coveted prize is the critical Serdes. Gennum Corp. and National Semiconductor are among those offering or planning to offer discrete Serdes solutions for 3G-SDI, while Altera and Xilinx provide the technology in FPGAs.

Richard Doherty, research director at the Envisioneering Group, doesn't expect a clear victor anytime soon. "Some will use National, some will use FPGAs. It will be a battle for quite a while."

"From our point of view, it depends on the application. There is room for both," said Stan Moote, VP of business development at Harris Corp.'s Broadcast Communications Division, a supplier of broadcast video equipment. FPGAs are better suited for higher-end systems with multiple channels, Moote said. ASICs or ASSPs may be ideal for systems with fewer channels, he said.

Serial digital interface evolves to rev HDTV transport rates in studios.

'Intelligent partitioning'
National sees a shift toward "intelligent partitioning," in which its analog-oriented broadcast chipsets work in conjunction with third-party FPGAs, said Stephen Kempainen, director of marketing for the chipmaker's Interface Division. National's 3G-SDI Serdes would perform the analog functions while the FPGAs do the heavy lifting in the digital domain, such as raster support, scrambling, CRC and line number insert. "I would not call it a collision course," Kempainen said. "We cooperate with Xilinx and Altera. It's competitive cooperation."

For systems houses and chipmakers alike, the SDI stakes are high. The broadcast equipment market overall is growing at an annual clip of 5.3 percent and is projected to hit $10.4 billion this year, according to market research firm SCRI International Inc. SDI itself is a serial link used in distribution amplifiers, video routers, production switchers, cameras and other equipment at the major studios and TV networks. It transmits uncompressed digital video over 75ohm coaxial cable over a short range within a TV studio or related facility.

But the bandwidth of the high-definition SDI flavor used today is inadequate for newer video applications. Standardized as SMPTE 292M, HD-SDI enables uncompressed video signals at a nominal data rate of 1.485Gbps.

SMPTE 373M, sometimes called the dual-link standard, is an interim step in use today that combines two HD-SDI cables to provide data rates of 2.97Gbps. The 3G-SDI spec hits the same rate using a single, 75ohm coaxial cable.

The new standard enables serial transmissions of uncompressed video signals in 1080p (1,080 lines of vertical resolution in a progressive format) at up to 60fps. Today, 1080p video is produced in the studio, but outbound video to the home is still delivered in a 1080i (interlaced) or 720p (progressive) format. Thus, the first target application for 3G-SDI technology is digital cinema, which benefits from the higher-resolution video enabled by production in 1080p, said Michael Hendricks, marketing manager for broadcast video products at National Semiconductor.

The next step would be to propel the technology into the broader network. At present, dual-link HD-SDI technology can transmit 1080p video at roughly 25fps. The goal is to enable studios to transmit 1080p at 50fps or 60fps, Hendricks said. Production in 1080p at the higher frame rates with downconversion to 1080i or 720p improves image quality in HDTV transmissions and requires less processing than cross-conversion techniques, he said.

Most, if not all, of the major studios and TV networks expect to migrate from dual-link SDI to 3G-SDI technology, said Harris' Moote. "That's an obvious choiceit saves cost and wiring." But "in broadcasting, nothing happens overnight. We're looking at a couple of years," he said, before equipment is upgraded and ready in the field.

Chip solutions
Chipmakers are already gearing up for that day. Last year, Mindspeed Technologies Inc. rolled out a video cable driver for 3G-SDI; in March, it followed up with a dual-output video cable equalizer.

In September, Gennum became another early entrant with the HD-LINX III chipset, comprising the GS2974A equalizer, GS2975A reclocker and GS2978 cable driver.

The chipset works in conjunction with FPGAs, which handle the Serdes functions, said Alan Ferguson, director of marketing for the Video Products Division at Gennum. Over time, Gennum plans to develop its own Serdes devices for 3G-SDI. "The FPGA can't do everything," Ferguson said. "We think we can do it in a more cost-effective fashion."

Not surprisingly, Tim Do, technical marketing manager at Altera, disagreed.

Altera's FPGA-based SDI MegaCore solution, which has been out for some time, supports SD-SDI, HD-SDI and 3G-SDI on the same transceiver pin. It works with analog-based cable equalizers and drivers from Gennum, National and others, Do said.

Rival Xilinx has a suite of reference designs based on its Virtex-5 FPGAs. The ML571 evaluation board will let OEMs convert from dual-link HD-SDI to 3G-SDI with improved jitter performance, according to the company.

The board can be used as an interoperability testing platform for professional broadcast and digital cinema applications. "The Hollywood postproduction houses are interested in 3G-SDI," said Paolo Masini, senior manager of broadcast vertical marketing at Xilinx.

National has unrolled an end-to-end solution comprising a 3G-SDI chipset and a multirate Serdes. The Serdes portion consists of the LMH0340 3G serializer with integrated cable driver and the LMH0341 deserializer with reclocked serial loop-through. The devices work in conjunction with FPGAs from Altera and Xilinx.

The architecture uses a proprietary technique to reduce the parallel bus between the serializer and FPGA from a 20bit single-ended interface to a 5bit low-voltage differential-signaling interface, Hendricks said. That, in turn, simplifies board layout by reducing the number of traces among the serializer, deserializer and FPGA, he said.

National's 3G-SDI chipset comprises the LMH0344 adaptive cable equalizer, LMH0346 low-power reclocker and LMH0302 cable driver. Applications include routing, distribution, video production and image processing. Each device supports the SMPTE-424M standard and enables serial transmission of 1080p video.

The LMH0344 automatically adapts and equalizes signals from 143Mbps to 2.97Gbps, according to National. The LMH0346 automatically detects and retimes the incoming signal to reduce high-frequency jitter.

The LMH0302 drives 75ohm transmission lines from DC to 2.97Gbps. A power-saving enable pin lets the user disable the output driver to reduce power consumption to 76mW in standby mode.

- Mark LaPedus
EE Times

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