HD/SD under control - TvTechnology

HD/SD under control

The transition from 525/625-line standard definition to 720/1080-line high definition is well under way, spurred by the increased affordability of HD
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The transition from 525/625-line standard definition to 720/1080-line high definition is well under way, spurred by the increased affordability of HD equipment at every point in the broadcast delivery chain. At the front end, the HDV videocassette format allows 720p and 1080i 16:9 acquisition at a prosumer price point. At the display end, respectably large LCD television receivers are now competing fiercely for customer attention in retail stores.

Broadcast equipment manufacturing has gradually migrated from dedicated hardware towards software. The hardware approach allowed potentially high reliability but commensurately high price and low flexibility.

Software-only products initially appear more attractive. They combine low price and high flexibility. But they are only as reliable as the platforms they run on.

If these platforms are in turn engineered down to a price for multirole applications (e.g., the ubiquitous personal computer under Microsoft Windows control), the software manufacturer cannot honestly claim to have total control over the final product.

There is a third option: firmware based on field-programmable gate arrays (FPGAs). A single-chip FPGA can deliver most of the functions associated with a computer microprocessor. The flexibility and inherently low cost of FPGAs allows dedicated products to be developed almost as easily as software while maintaining tighter control over the stability of the operating platform.

How to buy: Think modular

Turning technical generalities into a specific purchase plan is best achieved by carefully studying current operational process paths and then mapping your entire system from incoming lines right through to playout. This exercise clearly identifies single-points-of-failure and shows the extent to which a current system can be expanded without having to be pulled temporarily off-air.

From that foundation, an expanded or entirely new process path can be mapped out on a module-by-module basis to incorporate each required additional function.

You may also find value in mapping out the process path of your entire organization. It is an extremely powerful way of identifying the strengths and weaknesses of any corporate structure.

Modularity is a valuable feature for today's television stations. Every designer plans and builds in a modular fashion but does not always pass the full power of that modularity on to the end user.

A multidefinition master control system should ideally be scalable from a simple SDI A/B switcher up to a full-blown mix/wipe/key/DVE/clock insertion master control combination by adding different modules. This makes the whole system flexible and configurable to individual clients' requirements. Equally important, it should be inherently easy to reconfigure to accommodate extra channels or a changing operational environment such as greater automation.

Figure 1 on page 38 outlines key questions for you to consider when planning a multidefinition master control switching system. Starting with the up-front considerations of audio and vision switching, it then works through the requirement options for automation, embedded audio, voiceover, downstream keying, and animated or static logo generation. Power supply redundancy and failsafe relay bypass then need to be factored in along with audio monitoring, file transfer interfacing, manual/motorized control panel facilities and so on.

Modular thinking does not necessarily mean you are obliged to implement modular solutions. However, the strength of a modular approach is the ease with which the system can be rescaled to match increased demand or modified to meet an unanticipated requirement.

Gearing up for 1080p

The most important decisions in any multidefinition system structure are at what points to down-res or up-res, and where to operate in dual-definitions. Don't forget to consider how the resulting process paths could impact overall operation if any one module or side-chain should fail.

With 1080p looking increasingly likely to become the worldwide standard for program origination, a cautious system integrator or station engineer may want to structure the entire master control system to operate at 1080p and leave all the down-res processing to the point immediately prior to playout. A well-designed modular system should allow the technical staff to make these judgments for themselves rather than them be limited by the rigidity of predefined hardware.

Multichannel presentation suites need fast and efficient control over channel branding logos, including the ability to handle static and animated artwork. Be sure the technology you select for your station can accommodate today's and tomorrow's needs.

Dual signal squeezeback processing with integrated keying is another valuable presentation tool. Consider, does your application need real-time delivery with picture-in-picture and image-squeeze applications? Do you need real-time horizontal and vertical resizing effects? While a modular approach is flexible, it's best to plan now for your ultimate needs so you'll be ready when those needs arise.

External controllability

The ability to control broadcast equipment from an external computer is particularly vital in the case of a master control switcher. Ideally, the system should permit a complete health check to be performed on new and existing installations, with automatic repair of any misadjusted parameters. Logging facilities should also be incorporated to assist integration with third-party automation systems.

IP-based fault-finding is increasingly taken for granted by systems integrators. It means that an engineer can check from a remote location individual modules all the way up to an entire network.

A long-term goal for this technology is the ability to monitor the whole system automatically using out-of-boundary sensing of key operation parameters. It can then trigger switch-over to a standby channel or request a human response.

Maintaining signal legalization is perhaps as essential in high-definition production as in standard definition. In fact, it might be considered even more so given the ease with which HD audiences can see image artifacts when viewing on large-size picture displays.

This usually necessitates 10-bit processing in the legalizer, which enables the master control operator to ensure that the station's output is within the levels set for the target delivery chain or transmitter. Some features to consider include independent adjustment of hard and soft clipping levels along with independent control of luma gain, chroma gain and black level, and power-protected user memories.

The latest generations of 16:9 wall-mountable LCD and plasma screens are selling well. However, 4:3 displays will inevitably remain commonplace for many years. This means that you will have to handle multiple aspect ratios and be able to verify that the program remains within the visible screen area for each of your output channels.

Selected safe-area markers are normally superimposed onto the HDTV video feed, which can then be viewed on a monitor display without being visible on the main transmission output. Commonly used guidelines include:

  • safe-action and safe-title areas;
  • center markers (short and full screen);
  • moveable horizontal and vertical cursors; coordinates indication;
  • variable aspect ratio box; and
  • edge blanking lines (analog and digital).

Preset aspect ratios should be switch-selected for all common film and television formats down to 4:3.

The multidefinition future

Program originators, post-production facilities and broadcasters in Europe, India, Latin America and Southeast Asia are following the United States' lead in introducing high-definition services. The transition will not be a straight switch from standard definition to high definition, but instead an expansion into multidefinition, meeting the demands of Internet-based broadcasting as well as terrestrial and satellite-based 525i, 625i, 720p and 1080i.

Multidefinition will be a standard requirement in television broadcasting for the rest of this decade and probably well beyond. Plan correctly now, and the transition will be easier for both you and your staff.

Martin Moore is the managing director for Eyeheight.