Building to Broadcast
Apr 1, 2004 12:00 PM, By Mel Lambert
Systems Integrators Develop All-New Audio/Video Infrastructure
Digital television has enjoyed a long gestation period from its bold and brash introduction a decade ago. For a myriad reasons, the availability of HDTV was delayed and on-air launch dates slipped forward. But consumer demand for receivers created by cornerstone productions such as The Tonight Show With Jay Leno, The Grammy Awards and The West Wing is rapidly accelerating. And with adramatically increased level of sports programming, hi-def is here to stay. Though it took a while to reach the public, broadcasters have not been idle. The key to any successful technical installation is a properly conceived and executed technical infrastructure.
Infrastructure is one of those oft-used expressions that can be hard to define, but for our purposes, in the media production industry, let's say it is the means by which data is transferred and distributed throughout a facility. The advent of digital technology has certainly broadened any manageable definition. Now, instead of relatively conventional balanced/unbalanced audio cables to transfer analog signals from place to place, we've added the complexity of real-time or on-demand streaming of digitized audio and video data. Data rates require more than just twisted-pair copper, so co-ax, fiber and other means of signal distribution are becoming commonplace. Also, with transfer of audio and video via Ethernet-based networked topologies, CAT5/6 and related nomenclatures are becoming more and more a part of our everyday vocabulary.
Furthermore, with the broadcast industry poised to offer — if not already embracing — standard/high-definition TV production, distribution and transmission, there is a pressing need to acquire, process and transfer ever-increasing amounts of high-bandwidth data streams. Fortunately, there now exists a new breed of systems integrators for whom this lexicography is familiar jargon — companies that specialize in analyzing the needs of a broadcast or post facility and turning it into a practical reality, one that will remain viable for the plant's projected life.
According to Scott Griffin, VP of engineering at The System Group (New Jersey), “A primary question to be put to the client is, ‘Green field or facility upgrade?’ It is an important difference and one that affects the reality of data infrastructures, because retaining legacy equipment and standards will [impact] what new platforms can be considered. It's also critical to know what the broadcast facility's programming needs will be, and whether those needs change dramatically during a work day. It therefore comes down to an interdependence between media flow and work flow. We identify areas where file transfers between servers and high-capacity storage systems can take the place of real-time streams, and we analyze areas of the operation where file retrieval and manipulation models can replace real-time stream processing and mixing. If the station will be handling a combination of live production and repackaged materials from a server or similar delivery system, then we need to devise an infrastructure that can handle the capture, manipulation and delivery of the appropriate range of material.
“In essence, we determine whether the transfer system is file-based — accessing a file and then delivering it to where it might be needed — or stream-based, where we need to deliver digital audio and video continuously,” Griffin adds. “If a file-based system is appropriate for the task, what are the computer platforms being used, and what are the file formats? We then select products that offer the best user interface and functionality, and also make a determination about whether a targeted manufacturer is going to be around to support the products for a reasonable amount of time!”
The system integrator will analyze media requirements more closely to accurately determine delivery bandwidth. “A facility planning, let's say, 30 user seats with bandwidth-intensive processing sessions dependent upon a central server will narrow the vendor choices because of the required bandwidth across the network,” he explains. “We're always looking for cost-effective solutions to our clients' objectives, but we are relatively conservative in our product selection. If we haven't observed first-hand that a given platform has addressed a given requirement in a working environment, then we'll visit facilities where a vendor or user group has successfully addressed that feature to see what is available. We develop a series of signal flow models that determine the high-level requirements — how to get the media from component ‘A’ to ‘B,’ and so on — as well as individual operations' work flows. Each edit suite, for example, will have its own storage and delivery requirements, as well as inflow/delivery of media based on the desired operator toolset. Finally, within each operations suite, we'll work with our client to illustrate the operations work space and identify the support equipment that will be required.”
Recent TSG projects include a new multimedia facility for PBS affiliate WVIZ-TV, Cleveland; upgrades for MTV Networks (including a new backup to Disaster Recovery Master Control Systems); station consolidation for Tribune-owned WXIN and WTTV, Indianapolis; Morgan Stanley's new East Coast — headquartered broadcast facility in Purchase, N.Y.; a new Broadcast Operations Center for CNBC's financial news operation in Englewood, N.J.; and Fox News' street-side studio in midtown Manhattan.
Once the basic infrastructure is determined, Griffin says, “We can develop the operator management scheme and move on to the execution phase. Basically, we now become general contractors for the project and work closely with the client's production team and engineering team, plus their architect and general contractor. The key to any successful design is project planning — the sequencing and implementation of each phase.”
In terms of networking, Griffin offers that the primary consideration is flexibility vs. broadcast integrity. “If it is an on-air facility with little post-production, we need to emphasize system reliability, which we balance against routing flexibility. Consider a system based on MADI routing, which might allow any mic to be accessed in any room in the complex. What happens if one of the fibers gets pinched? Or you might lose a feed to all the rooms if one clock source fails. In this case, we need one or more layers of system redundancy. We look at redundant power supplies, redundant node controllers [PC network interface cards], redundant disc controllers and multiple paths we can use to route signals. But if the design calls for a series of production environments, we can provide a means of swapping out vital elements. We do not need a high level of redundancy.”
Of critical importance to any infrastructure scheme is how to get signals from one location to another, either in real time via routers and dedicated highways, or by utilizing a real-time or packet-switched network topology. For dedicated highways, the choice is often between conventional balanced/unbalanced copper cabling and co-ax or fiber interconnects. “Copper is often a very cost-effective, non-complex way of taking care of the situation,” Griffin offers. “For networking, we typically have to combine GigE Ethernet and FireWire interconnect schemes at the desktop, with Fibre Channel, ATM and/or SCSI for server and data-storage platforms, especially when linear, uncompressed files are being moved around. The determining factor is Quality of Service and how the use patterns will stress the systems. From discussions with the broadcast client, we develop a statistical model that is based on 30 to 50-percent utilization and make sure that we can deliver the required bandwidths without interruption. But it's often an educated guess: While we can anticipate the delivery needs, in real-world applications, we cannot always model the entire system for worst-case maximum capacity usage due to financial realities.”
Recent TSG audio facility designs have incorporated MADI, TDIF, Dolby E and Dolby Digital, and audio over IP platforms; tape and disk-based storage elements also have been included. “The line between IT and audio transport and storage has been blurry for a long time,” Griffin says, “but some of the newer products available today present interesting applications and integration challenges.”
At Seattle-based Doyle Technology Consultants, the firm's director of engineering, John Hartwell, stresses the importance of determining the type of delivery system being considered by the facility owners. “We need to analyze the number of channels, system bandwidths, distances and wiring topologies,” he says. “If the final audio product is stereo audio, we can develop an AES3-format infrastructure. With multiple sources and multitrack wiring, we look at both AES3- and MADI-based infrastructures using fiber and copper for nonstreaming systems. But multichannel audio is becoming the delivery format for broadcasters — even more so in Europe — and so we need to accommodate 5.1-channel capacities. We prefer to carry audio as discrete channels, but if bandwidth is restricted, we will consider data compression of some sort. Dolby E seems to have a lot of the hooks we require and reduces the bandwidth by a factor of four. Up to eight audio channels can be carried over a conventional 2-channel AES3-format highway and/or recorded onto a conventional digital audio track that handles AES signals.”
SYNCHRONOUS, EMBEDDED AUDIO WITHIN SDI VIDEO
And 5.1-channel surround sound requires another infrastructure scheme for the companion metadata. “Because a broadcaster needs to come out of the PCM world and enter the Dolby Digital or AC3-encoded world for transmission,” Hartwell stresses, “we have to consider what happens to the important metadata during the translation process.” Doyle Technology Consultants, in partnership with Wohler Technology, is developing a VMC/Visual Monitor and Control System for this critical stage. “There is a lot of information carried within the Dolby E bitstream that needs to be passed on to the consumer to control; for example, dialog levels in set-top AC3 decoders,” Hartwell continues. “Also, the Dolby E bitstream might be carrying multiple-language versions of the same program material. Within master control, the operator needs to be able to extract the appropriate audio and add other elements. And we are also looking at asset management using metadata. While many of these applications might not be in use currently, we need to consider future developments.”
For networking of digitized audio and video, Hartwell considers, “We use what works! Full-bandwidth digital audio belongs on AES and MADI connections using copper or fiber via a nonswitched network. Data-compressed audio can be carried over a network connection, although we don't normally recommend such schemes for real-time delivery. Ethernet-based networks using conventional PCs and interface cards are okay for connecting workstations via a public network, but TCP/IP can be very slow and liable to interruptions. We can deliver files that are between five and 10-times real time using networks, but we have had few requests from broadcasters for real-time delivery. For our post facility clients, including Lucasfilm and Pixar, we specify real-time transfer over an appropriate network, because we can control bandwidth and access to highways. A dedicated DS3 network will carry 45 megabits a second.”
A. F. Associates is a leading systems integrator that has been involved in a number of design and construction projects, including American Production Services, NBC Burbank's The Tonight Show With Jay Leno (one of the first live network shows to be broadcast regularly in high-definition format), the Staples Center in Los Angeles, Madison Square Garden, National Mobile Television, Action Sports and Entertainment Network, Comcast Sports Network and a mobile truck for Core Digital. The firm is also handling design and fabrication of modular studio systems that will be packed into containers and shipped to Greece for NBC's coverage of the upcoming Summer Olympic Games. Director of technology Lowell Moulton emphasizes the use of synchronously embedded audio within SDI video bitstreams as a way of reducing the complexity of a facility's infrastructure, as well as saving weight, for example, in mobile trucks. “Such vehicles have an all-up weight limit of 80,000 pounds,” Moulton confides. “Anything that can save weight — including, for example, disk-based recorders and audio/video over Ethernet — can be a major design factor.”
NMT's HD2 hi-def truck required a number of I/O cables for each video machine. “Most video and audio signals were on single unidirectional cables,” Moulton recalls, “which means that many connections must be run to provide inputs, outputs and control signals to each device. Signal formats such as embedded audio in SDI interfaces, MADI and SMPTE 324M [a 12-channel AES-like protocol over co-ax] help reduce cable count by putting many audio channels on a single cable. In the future, the quantity, weight, volume and cost of cable in these trucks may be substantially reduced when all video, audio and control signals are multiplexed onto a single, high-bandwidth bi-directional cable such as CAT5e UTP and optical fiber. Weight, volume and cost are critical factors to truck operators.”
RELIABLE DATA NETWORKS FOR DIGITIZED AUDIO AND VIDEO
For the NBC 2004 Athens Olympics, the network had specified two
Calrec Alpha 100 and two Zeta 100 digital consoles. “We are using AES3 digital audio interconnects,” Moulton explains, “much of which is embedded into SDI video. And NBC is well-positioned to transition their Olympics productions from SDTV to HDTV. The 2004 Athens Olympics is wired with cable and connectors that will pass SMPTE 292M HD-SDI signals. We have measured production samples of each manufacturer's coaxial cable, BNC connectors and patch circuits using a 3-gigahertz Hewlett-Packard network analyzer. All components we have specified will provide excellent group delay across a wide range of frequencies.
“The Sony DVS 8000 standard-definition video production switchers [specified for the Olympics] can be easily converted to MVS 8000 HD models just by changing out [various component boards]; all wiring and control panels remain the same. By 2008, NBC coverage of the Beijing Summer Olympics should be done completely in HDTV.”
Regarding the use of data networks to deliver digitized audio and video, Moulton stresses that such topologies can be reliable, so long as several major design considerations are observed. “If we need to deliver guaranteed bandwidth for audio over Ethernet, then we use a packet-switching scheme, such as CobraNet. CAT5 cabling is a lot cheaper than multichannel audio and, because of its operational flexibility and use of off-the-shelf components, can be very versatile. We are also looking at AES47, which involves the delivery of multiple channels of AES-format digital audio using an ATM [Asynchronous Transfer Mode] network over single CAT5 cabling. [The format is being used experimentally in the UK by the BBC to connect between Radio 4 studios and to various transmitters.] Unlike IP-based connections, ATM offers extremely low latency [around 1 ms], supports mixed sample rates and bit depths simultaneously, and offers a routing and distribution structure that can be set up as one-to-one or one-to-many.” For example, the BBC uses 155Mbit/sec ATM highways to carry up to 40 channels of AES3-format 48kHz/24-bit signals in each direction. Two unused pairs on each CAT5 cable carry a “backup” AES3 stereo signal, plus a dedicated multirate sync reference.
“But we are convinced that Quality of Service must be provided for broadcast-quality audio and video over IP networks,” Moulton stresses. “Some of the QoS techniques we're exploring with network vendors include over-provisioning private networks, priority queuing using DiffServ and IntServ [protocols], forward error correction on low-latency paths and Multi-Protocol Label Switching for traffic engineering.”
Based in Virginia, HA Design Group recently completed a new facility for al Hurra, the government-run, Arab-language satellite television channel for the Iraqi people (formerly known as MTN or Middle East Television Network). The new channel was launched earlier this year to compete with al Jazeera and other Arab television networks and, according to a government statement, “will bring balanced reporting on international issues to an area of the world where one-sided coverage is the norm.” The production and broadcast complex currently houses an on-air studio and control room, 10 edit suites and a number of news-preparation workstations.
HA Design Group president Willy Halla was formerly with TGS Inc., a company with a solid track record in DTV and HDTV conversions. “For the MTN [al Hurra] project, we had looked at a way of using a shared-resource, software-based plant. As far as the audio consoles were concerned, there were a lot of potential vendors. In the end, MTN chose Lawo AG. That decision gave MTN [assignable digital] audio boards with an extreme amount of power and flexibility — flexibility was key — and yet they are very easy to use. In fact, the Lawo system is being introduced to the U.S. market at MTN, which is located in Virginia.
“A MADI distribution system is used for the digital audio paths while an Ethernet system handles control of source routing. When the Lawo software is completed, it will be able to assign any source on any audio board in the plant to a specific fader on the target control surface.
“The use of MADI has cut down greatly on the amount of cabling needed,” Halla says, “thereby reducing installation cost. Also, instead of using standard metering that would have cost between $4,000 and $5,000 on the larger audio console, we used a PC/LCD screen combination that costs $1,500, yet provides greater functionality. The screens can also be set to display the dynamics section of each channel.
“Thirdly, the [al Hurra] plant is server-centric,” Halla stresses. “Everything goes to the server. We have over 100 workstations on the network that are all capable of video and audio editing, accessing newswires, etc., plus standard office modules. We are distributing the audio news channels via streaming audio on the facility's Intranet, providing access to these via the desktop with the added ability to record a piece at will.”
Mel Lambert heads up Media&Marketing, a full-service consulting service for pro audio firms and facilities. Visit him at www.mel-lambert.com.
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