Counting On Conversion

Regardless of their success in launching HDTV services, broadcasters will continue to deal with scaling and conversion issues as they upconvert archival material to HD and, in some cases, downconvert the HD output for legacy SD receivers as mandated by market forces or regional legislation. Both SD and HD content will need to be handled by broadcast facilities for years to come, so it makes sense for facilities to invest in the best technology for upconversion and to choose infrastructure and production gear that can handle both formats with equal ease.
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Though an increasing number of broadcasters can now say they’ve completed the transition to HD broadcasting, many facilities will still operate with islands of analog, SD digital, HD and file-based equipment that must be interconnected to ensure that all media resources can be used effectively in program production and broadcast.

Among the most important elements in conversion for HDTV is implementing the right conversion technology to handle SD and interlaced material. The quality of a facility’s conversion gear and suitability of its workflow can have a significant impact on the end product delivered to viewers. Most solutions available today are based on linear, motion-adaptive or motion-compensated conversion technologies, and each offers benefits appropriate to different broadcast applications.

High-density playout applications or lines-in/lines-out applications dealing with a high variety and volume of conversion are best served by modular infrastructure and conversion products. Typical users of such solutions would include a playout center working with many incoming feeds in many formats, a multichannel transmission facility playing out channels in SD and HD formats or even the live production environment, such as in an OB van.

Modular decoder/synchronizers provide front-end processing for any type of input coming into a broadcast facility. Features such as video decoding, frame synchronization and noise reduction help ensure maximum picture quality while minimizing downstream compression artifacts. Higher-quality systems are capable of extracting the most possible information from analog picture sources, which in turn helps to maintain the value of media throughout the transition from analog to digital or from analog direct to HD. Some modular systems include full-frame synchronization with horizontal and vertical phasing controls, which allow the output to be timed to a facility’s master clock, as well as proc. amp controls.

Synchronizing HD/SD-SDI upconverter, downconverter and crossconverter solutions also helps users complete the transition between SD and HD formats in multirate broadcast operations or variable input/output environments. These types of solutions convert SD-SDI signals to HD-SDI and vice versa and crossconvert HD-SDI signals of the same frame rate (1080i and 720p). Fixed-mode aspect ratio conversion and closed-caption support for analog line 21 formats help to automate and streamline the conversion process. Various levels of audio support include handling of embedded PCM and non-PCM audio, processed alongside the video signal.

Though more and more people are paying a premium for HD content, there is still a limited amount of HD content available. To fill this void, broadcasters have been searching for affordable means of outputting HD content. Until recently, the choice of solutions for high quality HD upconversion has been slim. Now this is changing, but most products appropriate to the task have been designed for the post-production market—or simply haven’t been designed with the level of conversion quality necessary to provide viewers with the visual standard associated with HD pictures.

If HD is to succeed among consumers, broadcasters who opt to retain an SD infrastructure for their production operations will require a solution capable of providing the stunning quality this technology promises without the expense of upgrading an entire facility to HD. Likewise, the cost-effective multicasting of an SD channel in HD from a broadcast or transmission facility requires a system that will allow for provision of HD services without compromise to the quality of a network image or brand. This kind of implementation also applies in mobile productions that are produced in SD but distributed in both SD and HD.

Upconversion is the most difficult of conversion functions because it involves creating something from nothing. In the case of upconversion of NTSC material, it means generating pictures that are twice as high and three times as wide, or nearly six times the area of the original image. One of the greatest challenges in HD upconversion is to ensure flawless results regardless of the type of material being processed and the amount and variety of motion it contains—whether it’s action-packed sporting events or graphics-rich commercials. A further complication is that the majority of video material to be upconverted is likely to be composed of a mixture of sources such as film with its 2:2 and 2:3 cadences, mixed film and video, captions, graphics, logos and, most importantly, station branding.

The system must be automatic, work reliably with repeatable performance and output video with the barest minimum of conversion artifacts. Automatic handling of all these elements in the live environment and at a very high quality has been available in several incarnations, but never in a comprehensive system capable of delivering true HD quality in all aspects of the broadcast. The resulting broadcast will look good most of the time, but not all of the time. This is one of the greatest challenges presented by HD upconversion.

Conventional HD upconverters use either linear or motion-adaptive processing techniques, both of which tend to produce visible artifacts. Linear conversion involves processing compromises that can create motion blur or softness in the output and adaptive mode switching causes random intermittent loss of clarity and definition, as well as producing objectionable artifacts on all but the simplest material. With both these approaches, the maximum vertical resolution possible with a moving video scene is half the resolution of the input. This means that HD upconversions are always completed at a lower resolution than the SD video source.

Snell & Wilcox’s newest contribution to the HD conversion market is the 1RU Quasar Ph.C motion-compensated HD upconverter, which employs its unique FormatFusion process. FormatFusion ensures that each individual element and characteristic of the picture is seamlessly processed with absolute precision, using the most appropriate conversion algorithm to guarantee a clear and sharp HD output, regardless of the nature or complexity of the source material.

In fast-paced sports action, detail and definition around key parts of the images such as the ball or player is critical to the overall quality of the picture. Quasar Ph.C uses phase-correlated motion estimation and motion compensation to ensure full resolution and well-defined motion. The magic of the Quasar is that it is capable of providing this post-production-quality processing without any user controls. It’s a plug-and-play solution featuring hands-free operation and the highest-quality conversion. Additional compression pre-processing capability allows call-letter stations to work better with lower-quality sources requiring noise reduction and to squeeze HD content into sometimes-limited amounts of bandwidth.

Given that broadcasters will need to live with both SD and HD for years to come, the best solution for live production is one that makes no distinction between these formats from the point of the user. The solution is a multiformat SD/HD switcher that can handle both formats within the same mainframe and control panel with complete transparency, in realtime.

The Snell & Wilcox contribution to this market is the Kahuna multiformat SD/HD production switcher, which allows the operator to mix SD and HD content while working on a single control panel, allocating mix/effects banks (M/Es) to either SD or HD sources, or mixing the two together on a single M/E.

With upconversion integrated into the live production workflow, facilities needn’t invest additional dollars in external processing gear. Instead, they can extend the useful life of their existing SD hardware and take a gradual and selective approach to the purchase of HD gear rather than investing in systems such as HD upconverters, new HD graphics capabilities and new HD cameras in order to move to HD production.

Ian Ellis is product manager, conversion, for Snell & Wilcox.