Compression
By Jim Boston
The art and science of compression continued its onward, and upward, march at this year's NAB. Some claim that compression products shown this year can deliver the same quality using a third of the number of bits as was required by offerings just eight years ago.
Compression exhibits at NAB included demonstrations of new products that use fewer bits to deliver higher quality content.
Improvements in compression algorithms, hardware and noise reduction technology have led to a 10 percent to 15 percent decrease in bits required for comparable quality from one year to the next. The common toolkit used by most compression systems is still MPEG-2. But MPEG-4 is increasingly present, and MPEG-1 is still around, as the streaming folks still find it computer-friendly.
HD seems to be slowly moving to critical mass. Neil Brydon, product marketing manager for Harmonic, noted “significant interest from the ATSC, cable and DBS space,” attributing the increase in interest to factors including competition between cable and DBS, more HD content and a reduction in the cost of HD receivers.
The theme of increasing efficiency in MPEG compression was demonstrated by a significant number of telco suppliers at the show. Harmonic showed delivery of two broadcast quality video signals over a single DSL line. Optibase demonstrated a TV streaming platform designed for streaming multiple live channels over broadband networks such as DSL, fiber and Ethernet LANs. Compression is also transforming the architecture of cable systems. Instead of the traditional RF multiplexed approach to sending services from headend to the home, telco and computer LAN topologies are now being employed. SONET rings carrying MPEG wrapped in ATM is one approach that cable is using to upgrade their systems. Another approach is Gigabit Ethernet. A single Gigabit Ethernet LAN can handle approximately 250 SD television programs, thanks to the ever-increasing power of today's MPEG encoders. The topology used in such an approach would be MPEG over IP on Ethernet from headend to QAM devices that reside in distributed hubs near the viewer. The capacity that compression and telco technologies bring to the game is allowing the rollout of video-on-demand services to be offered in a growing number of locations.
Just as video servers have become closely aligned with asset management, compression systems are beginning to be integrated into asset management. Francois Abbe, a product manager at Snell & Wilcox, points out that broadcasters have realized that media asset management is fundamental to the workflow of a new business. The problem he sees today is that there are many media asset management systems, but few asset creation systems. By ingesting content and creating metadata effectively from the start, the broadcaster has relevant information about the content that will help to index that content properly. Once ingesting is done, the broadcaster can have accurate shot-change information and can know exactly what is in those shots. Down the line, it will help to distribute content outside of the main distribution channel, which in most cases is the broadcast television station. This content can also be sent to Web sites, or from business to business. Content owners now have the potential with ingest and management systems to reference content, advertise it, and put it online for a faster turnaround and greater return on investment.
Compression technology enabled the video server to take root and rapidly come to dominate the storage realm in television. As such, servers and many VTRs today have embedded compression systems. Therefore, these vendors face many of the issues that vendors of stand-alone compression systems face. Doremi Labs, a manufacturer of HD disk recorders, points out that the MPEG-2 standard maximum bit rate is 100 Mbits/s, which covers only high quality broadcast equipment, but not high quality editing equipment that requires higher bit rates. In addition, there is no standard defined for compressing 10-bit component video.
According to Jay Adrick, vice president of strategic business development at Harris, the continual evolution of compression systems are constantly evolving, with bit rate usage improvements, simplification of GUI control, the introduction of lower cost encoding and the addition of options such as stream remultiplexing.
ATSC encoders continue their feature growth. More broadcasters are becoming interested in statistical multiplexing as they put multiple program streams into their ATSC MPEG transport stream. Increasingly ATSC multiplexers, which can contain multiple encoders, act like master control switchers. Some can switch between network “pass-through” streams and multiple locally encoded streams by rapidly assigning a program ID (PID) from one program stream to another. These systems can also key like a switcher as the number of encoders that provide bug insertion to brand the station, and even individual program streams, continues to grow.
AgileVision, which was recently acquired by Leitch, is a good example of a compression system moving past the master control stage and into what they call a “DTV station in a box.” The AgileVision box not only does MPEG encodes, switches and keys over live MPEG HD, SD or data, but also drops/adds programs from the incoming network transport stream and handles Emergency Alert System requirements. As additional evidence that distinctly different technologies increasingly find themselves in the same box, the AgileVision system also can store incoming MPEG streams, generate PSIP and act as an automation control system. Jerry Berger, vice president of marketing for AgileVision, points out that using the AgileVision system also allows you to “localize” your DTV transmission of network programming and meet the other requirements posed by DTV.
Let's look at a sampling of compression solutions introduced at this year's NAB:
Harmonic has a number of new items at this year's show. Their DiviCom MV400 HD encoders are now enabled with variable bit rate capabilities for statistical multiplexing. Their systems are able to statistically multiplex HD, SD and data. They also showed expanded adaptive behavior in the MV50 encoder with its ENRGY intelligent noise reduction system, which attacks noise only when it is present. Harmonic also introduced Narrowcast Services Gateway for cable video-on-demand deployments. The gateway employs Gigabit Ethernet to increase video-on-demand (VOD) network scalability and capacity. They also introduced a Broadcast Network Gateway for HD and SD digital turnaround applications in cable networks. This product accepts four program inputs and provides either two ASI or two 256 QAM RF outputs. The ASI is intended to feed downstream scramblers for premium channel use.
Harris introduced the NetPlus HD IRD to complement the HDP 100 FlexiCoder, which encodes HD video. NetPlus decodes both 4:2:0 and 4:2:2 HD signals in most formats. NetPlus accepts satellite RF input signals as well as ATM- and ASI-based transport streams. CBS uses Harris FlexiCoders and NetPlus IRDs to support their HD contribution and HD network distribution requirements. Harris also introduced two new FlexiCoder modules, the EVA 162 for single-channel SD 4:2:0 applications, and the EVA 210 for dual-channel SD 4:2:0 applications. Both have optional statistical multiplexing.
Microspace Communications of Raleigh, NC, featured four live video and data demonstrations centered on the company's Velocity digital broadband satellite-based delivery service. They included MPEG digital video at 1.5 Mbits/s, streaming video to a desktop over 512 Kbits/s video channels, video-to-TV and video-to-PC solutions, and Velocity's File Forward service — a pay-per-megabyte means of delivering bandwidth-intensive corporate data or similar business-critical content.
Optibase introduced the latest version of MGW 2000. MGW 200 transmits multiple channels of live TV and video-over-IP networks. It can receive up to six live analog signals, encode them in real time to MPEG-1 or MPEG-2, and then stream them over an IP network in multicast or unicast mode. MGW 2000 also supports near on-demand transmission of 10 prerecorded streams, including MP3 files. The latest release, version 2.7, supports low latency and scheduled encoding and streaming. Optibase has also released the MGE-200D FD1, an entry-level digital MGW encoding module.
Stellat announced preparations to launch a new satellite in May. Positioned at 5°W, Stellat 5 in C-band provides full connectivity with the United States and near Asia, and high elevation angles across Europe, Africa and the Middle East. The satellite features four 72 MHz and six 36 MHz transponders. The satellite supports a variety of applications, including TV and Internet content distribution and IP backbone connectivity.
Snell & Wilcox introduced Ingest Station, which is used for compressing video (SD or SD/HD) for archive storage and broadcast playout. It is intended as the front end of a media asset management system and uses proprietary and open standard technologies including Ph.C phase-correlation motion estimation technology, and MOLE. MOLE is metadata about how video was initially encoded into MPEG so that MOLE-aware devices that decode the MPEG stream can re-code the video back into MPEG with minimal loss of quality. The Ingest Station is designed to achieve the quality content while generating relevant metadata so that the user ends up with an MPEG-2 master plus data for the media asset management system.
TANDBERG Television introduced the E5710 and E5720 ATSC SD encoders. These are targeted at broadcasters looking for a cost-effective solution to begin ATSC transmissions. The E5720 has six expansion slots and will have an HD upgrade card in the future. TANDBERG Television perceives a number of issues that have affected ATSC encoder sales, and they say that their new encoders address those. Barry Hobbs, director of new technology for TANDBERG Television, notes that the modulation debate and early lack of HD programming coupled with the high cost of DTV consumer electronics have prompted many broadcasters to delay implementation of their DTV channel for as long as possible.
Compression has become central to television operations, from acquisition through storage and on to transmission. While the compression efficiency slope might not be quite as steep as the computer industry's Moore's Law (computing power will double every 18 months), compression itself is rapidly becoming a pervasive utility that binds the source, be it video, or even multimedia, with the viewer. Given that compression is central to DTV, it is understandable that compression vendors are branching out in an attempt to handle more of the broadcasting process.
Jim Boston is a West Coast consultant.
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