DTV Answer book

Questions? We’ve got answers! Technology, business, standards, consumer acceptance and equipment selection are issues on the minds of most professionals. Trouble is, where can you get the “inside” information on trends and technology? Broadcast Engineering coordinated a group of experts and surveyed them on the top issues facing production and broadcast facilities. Headed by leading technologist Craig Birkmaier, key experts in five subject areas were asked to provide their professional guidance on these topics.

What are the benefits of 24p,and for what applications should it be considered?

By Larry Thorpe

The advantages of 24p center largely about the augmented creative capabilities facilitated by this digital production system. 24p digital acquisition offers new creative freedoms when compared with shooting on film. While all of the craftsmanship of the film director and cinematographer – in terms of lighting, filtration, lensing, framing, etc. – is fully utilized in 24p digital shooting, the digital camera further empowers them both. The camera allows real-time intervention to the imagery being shot – aided by the presence of a large-screen HD monitor on set. Picture sharpness, tonal and color reproduction can all be digitally altered to refine the imagery to a chosen aesthetic look. On the audio side, the 24p camera includes the capability to record up to four tracks of 20-bit AES sound. Being inherently sync-sound this can be a special boon on location shooting.

The 24p camera has impressive operational sensitivity – combining in one acquisition package the equivalent of a very slow-speed low-grain film (an exposure index of perhaps EI 50 – for shooting in brightly lit scenes), with instant switchability to effective high-speed operation (exposure index around EI 1000 – for image capture in deeply shadowed or nighttime scenes). This obviates the need for the later “matching” of different film stocks within a given production. The visible economic benefits lie in the low cost of 24p tape vs. that of 35mm film stock, the absence of processing costs, lower shipping costs and, in the case of television production, the absence of telecine transfer costs. This lowering of “front-end” costs offers better cash flow management on a production.

The 50-minute load of the 24p cassette can greatly lower costs in the case of underwater and aerial shooting, and on difficult location shooting. That same long record time compared to a 35mm film load can expedite uninterrupted multiple takes – thus maintaining spontaneity and emotional dynamics between the director and talent. This too has been reported as saving time and, hence, related costs.

Being digital, the 24p capture can expedite the creation of blue/green screen imagery in that the related compositing can be viewed in real time and in high resolution. This further facilitates optimization of lighting, framing and camera moves, contributing to a considerable speed-up of a traditionally time-consuming process.

The digital capture and downconversion abilities within the 24p VTR expedite the offline editing process. This has proven a major boon in improving workflow on episodic television production where rigorous schedules are the norm. The low noise in 24p imagery allows wider latitude in post production – tape-to-tape color correction or digital image manipulation in workstations—that can be particularly beneficial when the final output is transferred to 35mm release film. Workflow innovation will be dramatically extended as new metadata capabilities are incorporated into the total 24p acquisition and post production system.

Larry Thorpe is senior vice president, content creation systems, for Sony.

By Jeff Rosica

Production in 24p has some very obvious benefits. The first, since commercial production is a business, is the cost savings over film stock and lab fees. Compared to 16mm and 35mm film stock and lab fees, a 24p format tape cassette is extremely inexpensive. The longer the shoot schedule (with more takes and more coverage), the greater the savings that can be realized by shooting in 24p.

Another major consideration is whether the spot will have complex CGI elements. If the raw footage is already electronic, there is savings (in time and money) in not having to telecine the film in order to import shots into a CGI system.

One caveat to 24p is that commercial production is also an art form, and quality matters. On the small screen (the television), the characteristics of 24p might not appear so obvious to the untrained eye, but they exist nonetheless.

Producing in 24p takes a little extra care as you first enter the medium. Those who have seen 24p say that it doesn’t look like traditional video or film, but something else. It is a different look, but electronic filtering can make 24p “appear” like specific film stocks or video. In this way, 24p electronic footage can be almost seamlessly intermixed with existing film footage (stock footage, for example), especially since 24p’s frame rate matches that of 35mm film.

Today, 24p electronic cinema production (1920x1080) does not have the same resolution as film (2048x1536). In fact, the most common HD recording formats offer significantly less resolution than film with the ability to record only 1440i (HDCAM) or 1280i (DVCPROHD) pixels. True 1920x1080i recording on tape is only available on D5-HD and the Thomson VooDoo Media Recorder (D6-based), which records HD uncompressed.

Film will always have its place in the production world. It truly is a question of the right tool for the right job. For an electronic format such as 24p to truly be equal in quality to film, a mindset change needs to happen. We have to stop thinking of 24p as “video” and start thinking of the images that are acquired as true “electronic cinematography” or “virtual film.” To provide a true choice of formats (film or electronic), the 24p signal must not be processed like video. The 24p signal must be a full, unfiltered, uncompressed 4:4:4 signal with full color RGB gamut from the camera.

The camera itself must output everything that falls on the sensors without any modifications. This may be an idea that is hard to swallow for video people used to traditional video processing, but 24p isn’t (and shouldn’t be considered) video.

Jeff Rosica is vice president of Thomson Multimedia Broadcast Solutions.

Is DTV now a two-step (first low power, then high power) process?

By Bruce M. Allan

The FCC’s action of Nov. 8, 2001, on low power requirements could conceivably offer some relief to smaller market television broadcasters from new expenditures to meet the DTV transition deadline.

At first blush, this two-step approach looks promising. For broadcasters that are under budget constraints, low power equipment may not require costly modifications to the existing facility.

Television broadcasters may be able to use their existing tower as it stands or place a low-power transmitter and antenna on the broadcaster’s STL tower, if the studio is centrally located in the city of license.

There are several drawbacks to broadcasting low-power digital television. First of all with cable carriage unresolved, how is the broadcaster going to get that signal into the home? Penetrating houses and buildings attenuates the signal to a large degree and set-top, in-door antennas with decreased gain capabilities (over conventional outdoor antennas) degrade signals further. In other words, a broadcaster may end up with a limited coverage area and frustrated viewers.

With low-power transmission, the ability to cover a station’s city of coverage depends on the location of the transmitter. If the transmission facility is located outside of the city, then chances are the low-power transmitter will not be able to provide full coverage. And if their competition decides to go full power for the digital transition, then the broadcaster runs the risk of losing viewership to the stations offering the extended coverage.

Ultimately, a two-step approach to the transition to digital may satisfy the FCC’s new digital rollout rules. This action provides new opportunities for stations to cost-effectively get DTV on the air, but it also may raise competitive business issues for each station to consider.

Bruce M. Allan is president and general manager of Harris Corp., Broadcast Communications.

By Dane E. Ericksen, P.E., CSRTE

In its Nov. 15, 2001, Reconsideration Order to MM Docket 00-39 (the “DTV review” rulemaking) the FCC decided that DTV stations would be deemed to have met their May 1, 2002, on-air deadline (May 1, 2003, for noncommercial DTV stations) if they build facilities that place a DTV “city grade” contour over their principal community. What many broadcasters, and possibly even the FCC, may not realize is just how low an ERP this allows. For example, Table 1 lists DTV stations (all UHF) in four example markets, all with construction permits already granted for either maximized or class maximum DTV facilities.

These ERPs are based on continued use of the permitted, high-power antenna, generally top-mounted or side-mounted near the top of an existing tower.

I believe that such power reductions are typical; the FCC decision to only require the ERP necessary to place a DTV city grade contour over a station’s principal community turns out to be a breathtaking reduction, typically on the order of 20 dB to 30 dB below the station’s allotted ERP.

Does it make sense actually to build such low-power DTV facilities in order to meet the FCC deadline? Probably not, for two reasons: First, it is unlikely that such low ERPs would provide usable service, particularly in light of some recent technical papers suggesting that the FCC got the DTV threshold contour too low by 10 dB to 20 dB. Second, if a DTV allotment has tolerable interference from an existing NTSC full-service TV station, that interference could become intolerable for a “micro power” DTV facility that just meets the new FCC minimum coverage requirement. This is because the interfering NTSC station will not be lowering its power, so the desired-to-undesired signal ratio will then also be worsened by 20 dB to 30 dB.

It probably makes sense for stations fortunate enough to have received in-core DTV allotments to go ahead and install their permitted high-power transmitting antenna and large transmission line, but for now only install a 100- to 500-watt DTV transmitter.

Such low transmitter power outputs (TPO) will likely meet the DTV city grade requirement and represent virtually no “lost assets” to be discarded when higher operating powers make economic sense. For IP DTV stations with out-of-core assignments, the opposite likely makes sense: forget building a high-power DTV plant, and instead purchase a low-power LPTV/TV translator antenna, use 7/8-inch or 1 5/8-inch transmission line, operate with 100 to 500 watts of TPO, and take the FCC up on its “gift.” One exception might be for a UHF NTSC/UHF DTV combination where the NTSC antenna is either in marginal condition or where a broadband UHF panel antenna can be used, allowing an immediate benefit for the station’s UHF NTSC signal.

Dane E. Ericksen, P.E., CSRTE, is senior engineer, Hammett & Edison, Consulting Engineers.

By Harvey Arnold

The FCC’s recent decision to relax its rules on minimum DTV coverage is a very welcome and reasonable response to the broadcast industry’s concerns relating to the digital conversion. It recognizes the range of difficulties and realities broadcasters face in rolling out DTV, and acknowledges the size and scope of the efforts needed to transition the consumer and our industry from one technology to another. By the end of this year we expect to have about 40 of our 62 stations on the air with DTV.

From the beginning, our plan was to “build it right the first time” using a maximized full power RF design. That way, we don’t have to go back and rebuild the plant at a later date. The downside to this approach is that it takes longer to implement because of factors out of our direct control.

Since there are few over-the-air DTV receivers in consumers’ homes, initially, the FCC’s decision will allow us to realize common sense power savings in operating expense during the rollout, while still serving our digital viewers. Sinclair is installing high-power transmitters, but initially operating them at lower power levels.

We would rather be broadcasting at full power and supplying greater field strength throughout our entire market but, like most broadcasters, we are bound by fiduciary responsibilities to not keep shoveling money out the door when there are precious few working receivers. When the population of over the air receivers increases to that which CEA predicts in the next few years, we can then simply turn up the power to accommodate this audience growth.

Stations can take several steps to “work smart” when implementing DTV. First, exploit common antenna systems and community towers. The economics and synergy of multiple station towers are hard to dispute. The use of N-1, N+1 and community panel antennas generally do save money if stations can live with common antenna radiation patterns. Second, combine UHF and VHF transmitters into common transmission line systems and then split them out before the antennas. Combining VHF and UHF into a single transmission line is very practical when tower loading is an issue. This strategy has saved Sinclair the cost of constructing at least two new towers, and has little downside to either station.

Another step stations can take is to design a quality transmission plant. Put money into important items such as high quality antenna systems and transmitters that will be with the station for the long term. Remember that it is expensive to replace an antenna system because it can’t handle the power you need it to or has substandard radiation efficiency. Transmitters from many vendors offer similar performance. Take a hard look at ease of maintenance, cost of ownership and overall stability – these areas may drive you to a specific provider.

Finally, build for high power, but initially operate at a lower power during the transition. The savings in electric and other operating costs is significant. Increase power when there is a real need to do so.

Harvey Arnold is corporate director of engineering for Sinclair Broadcast Group.

What are some key features and capabilities broadcasters should look for in a new camera?

By Philip Livingston

Stations needing to replace existing cameras are in a quandary. Let’s first address the studio/field production situation. If stations buy standard definition cameras that integrate easily with the existing production switcher and infrastructure, Murphy’s Law dictates that the station will surely decide to go high definition next week. If they buy HD cameras, then it means replacing “everything” or paying for downconversion options that may eventually be superfluous. Nevertheless, it’s reasonable to assume that for local stations that have been just carrying prime-time network HD programs the studio(s) will be the next element to go HD. Clearly, what users need is an upgradeable camera that can be SD today and converted to HD when the need arises.

One option is a multiformat DTV camera system that supports variable frame rate capture and is upgradeable to a 720p or 1080i HD output. The CCD technology utilized by the camera plays an important role in ensuring a flat frequency response through the 30MHz pass band of HD systems. This technology provides greater sensitivity than a 920x1080 CCD. (While more pixels give better resolution, they also reduce the area of each site and therefore reduce the sensitivity.)

Broadcasters can utilize a basic SD camera with a built-in signal converter that provides a 480i standard-definition output from the high-definition 720p CCD signal in today’s TV studios. The super-sampling effect of having an HD imager and SD output produces high quality video. Having a selection of optional output signal processing modules available allows the unit to be cost-effectively upgraded to 720p or 1080i when the station needs to go to HD, and provides an economical path for broadcasters investing in a DTV conversion.

Once a station begins to consider HD studio cameras, the inevitable “news” question arises. While visionaries like WRAL-TV and groups like NHK are doing HD News, many broadcasters are not sure that this is the right approach. There are three factors to be considered: We regularly accept the fact that news field material does not look like studio material. Storage capacity and signal data rates are factors as news systems become ever more NLE and server centric. Upconversion technology is becoming better and more ubiquitous. Therefore it is easy to design a system where field material is captured, edited and stored in SD and upconverted just prior to integration (e.g. at the studio switcher), but upconverted 480i is perhaps not quite good enough. For many customers, 480p 60 appears to solve that dilemma.

Philip Livingston is vice president, technical liaison and technical spokesperson for Panasonic.

By Mike Wolschon

The process of selecting the proper camera for your use truly depends on two things: your need and your budget. First - your needs. Today’s digital cameras provide the utmost flexibility while shooting. The choice of aspect ratios (4:3 and/or 16:9), multiple camera configurations and digital signal processing in a number of digital cameras all combine to produce the best possible image.

While carefully considering the situation you need a camera for today, it is imperative that you give some thought to the camera’s uses tomorrow. Consider the relative importance of image resolution, light sensitivity, signal-to-noise ratio, faulty pixel correction, and the ability to precisely control detail, contrast compression, black stretch, and color temperature, as well as other digital signal processing (DSP) functions. Especially important is how automatic controls can be manually overridden.

A major consideration is the possibility of upgrading your standard definition camera to high definition. Can the camera you buy today for standard definition production work be upgraded for high definition or will you be repeating this evaluation process a few years down the road (with the added capital expenditures)? Cameras that provide this feature without sacrificing quality provides you the biggest bang for your buck today and tomorrow.

Once you have narrowed your camera search based on your performance criteria, a review of a camera’s physical size, power requirements, location of controls (buttons and switches), and location and type of input and output connectors is in order.

Questions to ask include:

Are there any parts of the camera that stick out (such as a BNC connector for video output) that can easily be damaged because of where they are located on the camera body?

If a portable camera, what is the total weight with camera head, lens, viewfinder, tape and battery?

If a portable camera, is there shared power distribution for on-camera lights?

If a portable camera, what is the battery recharging cycle time and how does that compare to the battery draining cycle time? If a portable camera, how easily can it be reconfigured for studio operations (viewfinder and lens controls)?

For a studio camera, how much power throughput is available for a teleprompter and timer?

Is triax available and what is the maximum cable length?

How detailed is the camera’s control unit and what is the maximum cable length of multicore cable?

If the camera has a switchable aspect ratio, which ratio is native and which is derived? How does this affect resolution?

Probably the best way to actually compare cameras without an actual shoot-out is to take the product brochures and create a chart with the features that are important to you.

Finally, there are always trade-offs: resolution for flexibility, design for cost, etc. Assigning a weight to each of the features in your comparison chart can help in selecting a contender for purchase. Using a point scale (resolution is worth 10 points and this camera gets eight out of 10) can make the process much simpler as you narrow your search.

Mike Wolschon is director of segment marketing for the North American subsidiary of Thomson Multimedia Broadcast Solutions.

By Juan Martinez

In the standard-definition world, choosing a camera to serve in both the studio and the field is a trade-off between the necessities of studio conformity and control and the necessities of field portability.

While we recognize that some broadcasters are moving to HD, we realize that most will continue to use standard-definition products, cameras and systems for quite some time. We want to optimize users’ investments with high-quality cameras and with an up-converter that creates worthy DTV material.

Consider one of the key requirements of a studio camera—the ability to control and color match the device from a remote control room or truck. Having a DV camcorder operable from up to 330 feet from its CCU over a multicore cable allows a single camcorder to serve both EFP and ENG applications. A composite video input allows news gatherers to record pool feeds.

Another issue is compatibility between all the competing DV formats. Camcorder tapes need to be compatible with various formats. Finally, there should be no compromise in quality, whether the camera is set up for studio or field.

With advancement in camera technology, the importance of the Internet is increasing. Broadcasters should factor in Web streaming capabilities in their decision to purchase a new camera. Some cameras can be controlled via the Web. Streaming adapters enable these cameras to be plugged directly into any network or even the Internet, after which the camera becomes an IP addressable device, producing MPEG-4 streaming video on demand.

Upconverters are available to enable users working in an HD environment to conform their SD materials to HD. An upconverter can allow broadcasters to take SDI signals, especially scenes shot in 16:9, up to DTV resolutions like 720p and 1080i while maintaining audio synchronization. Once converted, broadcasters can add true HD graphic enhancements and deliver programming at a fraction of the cost of HD origination.

The importance of this type of upconverter is that it broadens the choices of suitable cameras for use in DTV. Virtually any camera in a broadcaster’s current lineup can be pressed into a transitional paradigm.

We like to concentrate on where the real need is, not where it is going to be. These are tough times, and broadcasters don’t want to hear about tomorrow, they just want to survive today. We know there is still an increasing movement to an inevitable HD world. We also know that someday the Internet bandwidth will become a real alternative to broadcast. But we want to offer solutions that work right now, out of the box, with an immediate return on investment.

Juan Martinez is national products marketing manager for JVC Professional Products Company.

What role does IP networking play in today’s broadcast plant?

By Clyde Smith

IP is becoming ubiquitous in the broadcast plant, from production and post-production through delivery, it is increasingly difficult to find areas where it does not apply.

Let’s begin with system and system component performance monitoring. The Simple Network Management Protocol (SNMP) is the de facto industry standard today for monitoring and management of devices on data communication networks, telecommunication systems and other globally reachable devices. Today’s broadcast plants contain many, perhaps hundreds, of networked computers and computer-based applications. Monitoring and logging their performance is essential to maintaining and improving the plant reliability. SNMP is an enabler of this functionality.

The SNMP Agent software is typically a subsystem software module residing in a networked device. Many broadcast manufacturers are including SNMP, or bridges from their proprietary monitoring protocols to SNMP, to provide greater knowledge of system status and performance as well as control of system elements.

Now that we know we have a well-running facility, we need to get content into it, process the content and distribute it. The File Transfer Protocol (FTP), a standard Internet protocol, is the simplest way to exchange files between servers on a network. FTP is another application protocol that uses the IP protocols.

Whether it is to transfer commercials, promotional material or programming, file transfer has many advantages; from the avoidance of delays through customs when crossing borders, through reducing the need for repetitive visual observation quality control monitoring processes. Material is delivered to the plant, distributed to editing, then transferred to air playout servers all using FTP.

A file transfer and networked storage-based architecture can greatly improve the efficiency of operations by reducing the real-time video based digitization and layoff functions. This architecture opens up tremendous possibilities for intra-facility operations as well by providing multiple, relatively inexpensive, high-performance network connections between the Networked Storage Library and networked attached server, non-linear editing, graphics, media management and browsing clients.

In Distribution, if you accept the proposition that the “plant” is extending well out “into the rest of the world” through VOD, NVOD, Forward and Store PVR functionality and “Station in a box”, as well as central casting centers feeding remote transmission sites, IP plays a key role here as well. Distribution to these diverse “plant elements” may utilize traditional methods or IP.

With all its attendant advantages of potentially reduced acquisition costs, improved workflow and operational efficiency, intelligent monitoring and reporting of errors, the question becomes: Why would you try to build a broadcast plant without it?

Clyde Smith is senior vice president of broadcast entertainment technology at Turner Entertainment Networks.