Vivid dividends

Broadcasters need not shy away from investment in HDTV migration.
Delivery & Transmission
Delivery & Transmission

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Broadcasters need not shy away from investing in HDTV migration during tough economic times, as long as the correct future-proof infrastructure is introduced gradually to a broadcast facility, writes Neil Maycock.

These are interesting times for today’s broadcasters. Not only must they find ways to stay competitive and profitable in the worst global economic downturn in recent history, but they must cater to viewers whose sophistication is growing in proportion to the availability and affordability of high-quality HD-ready televisions. Therefore, for broadcasters large and small, migrating to HD operations is no longer a question of if, but when and how.

The basic concept of high definition has been around since the 1940s, but only in the last decade has the technology progressed enough to deliver the requisite storage capacity and processing power (enabled by advances in compression) to make HDTV affordable for consumers and profitable for broadcasters. The digital revolution and the emergence of compression standards such as MPEG-2 and MPEG-4 have been a huge driver for the growth of HDTV, enabling delivery of up to two HD or five SD digital channels with the bandwidth of a single analogue channel.

Current HDTV broadcast standards include ATSC (in the US and Canada) and DVB (in Europe and most of the rest of the world). HDTV also enables 5.1-channel surround sound audio using formats such as Dolby Digital (AC-3). The most common HD transmission formats are 1080i (1920 pixels horizontal x 1080 lines vertical – interlace scan) and 720p (1280 pixels horizontal x 720 lines vertical – progressive scan). The new 1080p format promises to deliver the benefits of both progressive scanning and high spatial (horizontal and vertical) resolution, including an inherent match to current flat screen display technologies (flat screens are fundamentally progressive), ease of conversion (up, down, and cross), and highly efficient compression.

Designing or converting a facility to handle progressive scanning requires careful consideration and an infrastructure that can handle a data rate of 3Gb/s, since progressive consumes double the bandwidth of interlace scan for the same picture rate and motion portrayal. Fiber optic technology can play a key role in handling the longer runs required by 3Gb/s signals – especially when paired with a high-powered router designed to handle fiber inputs and outputs. Also, modular interface and distribution products facilitate delivery of 1080p signals via mono-mode fiber circuits, both locally and over long distances between buildings or even intra-city sites.

The digital-HDTV revolution has presented some unique content challenges for broadcasters. Even before the economic crisis began to wreak havoc on budgets, converting immediately to a completely native HD production environment simply wasn’t feasible for most stations. The reality is that many content sources will continue to exist in SD format for the foreseeable future, and any HD operation must take them into account.

The best strategy for these stations is conversion technology that enables a smooth, gradual transition to digital, HD, and 3Gb/s operations by leveraging sources in many different formats. Today’s high-quality conversion systems give broadcasters control over image quality – with the ability to up-convert video from almost any type of source. The result should be clean and sharp high-resolution HD images. Various conversion technologies exist, but only motion compensation is able to produce near-perfect images when converting 1080i signals.

Upconversion provides a cost-effective method of migrating to HD by simply upconverting the SD program – but care should be taken when selecting a solution for this since this processing step has such a dramatic impact on picture quality as compared to a native HD signal. Phase correlation works by measuring “true motion” in the scene, identifying motion and content on a pixel-by-pixel basis to enable correct processing for each pixel, regardless of motion speed or content type.

As phase correlation operates in the frequency rather than the spatial domain, it is able to zero in on details while ignoring such factors as noise and grain within the picture. In other words, the system is highly tolerant to the noise variations and rapid changes in luminance levels that are found in many types of content – resulting in high-quality performance on fades, objects moving in and out of shade, and light flashes.

Production switchers that can handle a variety of formats and standards offer another highly effective and economical technique for HD migration, especially for live news and sports operations. Many current switchers have been crudely adapted to handle sources different from the system’s operating standard, and some only offer conversion on dedicated inputs. However, adding conversion functions to the front end of a switcher can add unacceptable latency to the video stream, often creating delays up to four frames or 0.16 seconds.

This is more than enough to create significant lip-sync and shot matching errors that can only be overcome by compensating delays to bring video and audio back into sync, but these do not address the overall delay that has been inserted by process-intensive equipment. Therefore, the solution is a switcher architecture that is designed to simultaneously handle any broadcast format or standard with absolute “zero timing” on all inputs and no differential delay between sources.

Networking and signal transport for an HDTV operation is far more complex due to the higher data rates required by each HD signal, which can limit cable runs. Effective timing of a system can be difficult to achieve given the variable data rates of the multiple signals required, and associated line timing issues.

A technically advanced router with fiber input and output, can make cable length a non-issue by automatically handling all signals up to and including 3Gb/s in a format agnostic manner.

An effective automation system is a critical success factor for any multichannel HDTV operation; providing the means to handle different file formats and aspect ratios and ensure that the correct format is broadcast at the correct time. In addition to reliably airing a scheduled playlist, an important aspect of any automation system is its ability to smoothly cope with unscheduled programming, such as sports and live events for example, when the timing and running order of a schedule can vary significantly. This degree of scheduling flexibility also offers the ability to maximise revenues from advertising and other sources.

A state-of-the-art HD automation system, allows the operator to directly interact with equipment such as a master control desk to update the running automation schedule. Besides the ability to manage and control devices, other important capabilities for automation include moving media from location to location, tracking content and metadata, converting files to the appropriate format for playout, managing and scheduling playout, and logging any and all relevant data. Such a system takes a “hub and spoke” approach to media management to allow segmentation of channels into playout pods, each with nominated channels and dedicated resources including media databases. The automation system provides the ability to share content between pods via asset mail bridging across pods.

The business of television broadcasting has never been more complex, with rapid changes taking place on multiple levels. Further complicating the picture is the emergence of delivery platforms such as video-on-demand, mobile TV and Internet television, which is putting additional pressure on broadcasters to offer HD content to viewers whenever, wherever, and however they choose to receive it.

A broadcaster’s best defence against technological change is an HD infrastructure that is well-planned, open, and future-proof. Systems designed from the ground up to make the transition as cost-effective as possible, while maintaining high quality standards, are the building blocks for an infrastructure that will enable a successful, long-term broadcast business.

Neil Maycock, is chief marketing officer at Snell.

HD for the ear

One of HDTV’s great benefits to consumers is the ability to deliver multi-channel sound, such as Dolby surround sound. In a typical broadcast operation, HD equipment for transporting audio signals typically supports 16 channels, or up to eight AES pairs – with Dolby E setting the standard for HD audio. Dolby E enables the high-quality transportation of eight mildly compressed audio channels in a single AES pair, with six channels dedicated to 5.1 surround and the remaining two for stereo.

While systems integrators and broadcast engineers agree that integrating the video path is relatively straightforward, dealing with the audio portion can be fraught with problems. This is particularly true in the handling of Dolby E, which allocates a single Dolby E frame for every frame of video. Since the Dolby E frames are shorter in duration than their respective video frames, they are separated by intervals or “guard bands”. Misalignment of the audio frames with respect to the video frames can cause significant problems, resulting in pops, clicks, or even complete corruption and failure of the audio service.

These common audio issues have led Snell to develop a range of solutions. Automatic processing modules from the company’s Vistek and IQ Modular lines are designed to eliminate such audio misalignment issues and simplify integration and system commissioning processes.

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