You're going to have to transmit digital signals. If you don't already have a plan in place, it's time to get moving.
Though questions remain about its particular manifestations, one thing for sure, digital television is coming and as broadcast engineers there are things that we can do to prepare for the inevitable.
- Have a plan - Gather as much information as possible about the direction your network or management is heading in terms of DTV and their expectations. Become part of the team. Capture the global picture and get it down on paper. Simple block diagrams, descriptive prose, wish lists, business plans, flow charts or just about anything you can document about where the station is heading will be enormously helpful. Develop your plan to at least the block diagram and signal flow level. As a systems integrator we are very big on having a process map on paper that takes all this into consideration. It makes it easier to see what must be done, and a plan evolves. It's a lot less expensive to change paper than concrete, steel and equipment. Consider utilizing as many assets as you have now with a simple phased approach to adding the digital capabilities.The simplest plan might follow this path:
- Establish digital transmission capability.
- Upconvert present analog program to DTV signal that matches your network feed and switch the DTV formats to air with a simple 10×1 switcher. Downconvert digital-only programming to integrate with existing analog facility.
- Build an HD-capable digital infrastructure even if you're only planning to broadcast single or multichannel standard-definition digital programming.
- Integrate existing analog signals necessary for the transition to the all-digital facility. Test analog and digital system off-line.
- Cut over to the all-digital system and place on-air.
- Re-purpose old analog system and components.
- Transmission - You're going to have to transmit digital signals. If you don't already have a plan in place, it's time to get moving. Many, if not most, broadcast facilities will have to add new antennas, transmitters and towers in addition to their analog transmission system in order to remain on-air while you're building the digital transmission path. It takes a long time to design, get approvals, and build those new towers, antennas and transmitters for stations across the country. Best to get in the queue now.
- The digital infrastructure- A good thing about DTV is that most of the signals the engineer will have to deal with are in a serialized digital format. It can travel down coaxial cable and is easy to terminate. While the various forms of DTV can include a wide range of data rates, the future-proof model is to design and build for the highest data rates that commonly exist today. At present, uncompressed serial digital data rates approach 1.5Gb/s with bandwidth requirements approaching 2.4GHz. Remember our goal is to create a digital island or digital facility that can handle anything that management or technology may throw at it. Luckily these cabling and components exist today and don't cost much more than what we have been using in the past. In the installation of any cabling system, the largest cost will be labor. It costs the same to pull, dress and terminate a cable/connector regardless of the material cost or quality. So put in the best components that exist and you won't have to do it again for a long time. Be careful replacing existing analog cable with digital cable in the same system, the cable has a higher velocity of propagation and different loss characteristics so they may not time or equalize properly with your existing equipment.
- Routers - If you already have an analog routing system in place and are happy with it, there is no need to replace it. Adding serial digital video and audio levels to your router may be possible if you purchased one that can be field upgraded and the frame can handle the data rates intended. You can always add these levels as additional frames but that will depend on the router control system and whether the manufacturer offers those components. Worst case, you can purchase a new control system that will work with your existing router frames and also the new digital ones you plan to add. Make sure the digital router can handle uncompressed HDTV data rates and also the Asynchronous Inputs (ASI) generated by digital compressed satellite systems. Because you may be working with your existing analog router frames and using A/Ds and D/As for integration with your new digital router/frames, make sure your control system has good path finding and tie-line management abilities. The user interface and how the router releases these tie lines are important.
- Switchers - If adding a digital production or master control switcher, choose one that will allow for multichannel/multiformat operation with a single control panel. Some are networkable which can prove to be useful. Choose a multichannel standard-definition DTV format having the ability to control them from one or more locations. A switcher that integrates tightly with your router will make for a more flexible system. Make sure the DVE will be tightly integrated with the switcher. The master control switcher is the one that will have to be the most flexible. You may need to switch your analog signal simultaneously with your DTV signal for a while. The HDTV signal may come as multiple standards from various sources that change throughout the day. Consider these possibilities when developing an initial plan and be sure the switcher will be flexible enough to handle these additions or changes.
- Networks - This is one area that will grow tremendously. Because Ethernet will be around for a while, you should build a solid, upgradeable 10/100Mb switched network. Use CAT 5 or better cabling and patching capability, which should handle most of the near-term applications. News systems are using Ethernet to browse ingested materials to servers from client workstations, perform low-resolution editing, control play-to-air functions and many other critical tasks. Higher bandwidth networks are emerging, each with its own set of assets and liabilities. Optical and copper Fibre Channel is evolving; however, it is peculiar to certain integrated systems. Production and graphic systems are making good use of it but, as an installed topology, I would add these capabilities as they are required. I foresee the Network Analyzer becoming as common a piece of test equipment as your present waveform monitor and vectorscope.
- Video servers - They are here to stay and will probably replace most VTRs for anything but portable use. Most use serial digital as standard I/Os with some offering analog as well. Use the analog I/Os today while you build your digital infrastructure. Transport streams are beginning to be more common for I/O. Multiple format compression codecs are in use and compatibility is necessary if you want to share. Think this one through carefully and consider all of your applications such as image quality, editing and recording non-synchronous feeds — they all don't perform the same. Also part of this game is storage for the servers. You'll never have enough storage, so analyze your requirements carefully. Plan for the inevitable growth. Leave space and allow for the AC power requirements and heat loads. Storage Area Networks (SANs) are getting popular for server and nonlinear edit file storage. Speed is important. File format compatibility between devices that share that storage is necessary and not always apparent, even between products by the same manufacturer that perform similar functions. Near online storage and archival storage is a must as your storage needs grow.
DTV is happening. Embrace it. You'll love it once you're in and it's just the kind of change you've been looking for. Treat it just like any other project that must be managed — plan it, organize it, implement the plan and control (refine) it. Be flexible because technology is changing quickly with fewer standards. Design for and build a solid infrastructure that can handle most anything that comes your way. Keep the pipes big and everything should fit down them. Leave room for expansion, if things get smaller or concentrated you gain space, if they grow, you have already planned for it and will accommodate it easily. Use a qualified systems integrator that works with many types of systems; their experience can be invaluable. Develop your plan NOW and don't wait until management wants it yesterday.
Gus Allmann is vice president and director of engineering for TV Magic, Inc.
