Broadcast Engineering - April 2008 - (Page 16)

TECHNOLOGY IN ACTION BEYOND THE HEADLINES Wavelet compression This technique promises a new way to upconvert SD programs to HD. BY TED TAYLOR ver since the necessity for international exchange of TV programs in electronic form rather than on ﬁlm, there has been a need for standards conversion. Over the last half century, equipment has seen much research and development effort to produce devices with improving transparency. Early devices used optical techniques, sometimes with remarkably good results for the day. In the late 1960s, huge analog frame store devices were developed using ultrasonic glass delay lines as the E for more and even better standards converters became paramount to address broadcasters’ needs for better quality at more affordable prices. The two key factors in choosing rate and format conversion equipment for the broadcast industry today are consistently high picture quality across a wide variety of content types as well as affordability. A small number of manufacturers currently produce devices that will deliver high picture quality, but the price tag is not attractive enough for Figure 1. Deinterlacing of mobile and calendar sequence. Upper left: line doubling. Lower left: spatial interpolation. Upper middle: time weaving. Lower middle: time interpolation. Upper right: motion adaptive. Lower right: Let It Wave’s deinterlacing. a fundamental need to use SD originated material in an HD TV environment. This requires an upconverter, which will be required in substantial numbers as the world migrates to HDTV over the next few years. Due mainly to the interlaced structure of SD television, upconverted pictures can often look worse on an HD display than the original on an SD display. This is despite the development of some complex and expensive technologies over the last couple of decades. A substantial change in expectations on performance and cost has been enabled by a new process referred to as Super-Resolution Bandlet Technology. This has demonstrated an improvement over current technologies while being implemented in a single medium-cost Field-Programmable Gate Array (FPGA). Super-Resolution Bandlet Technology is a set of mathematical image processing algorithms based on geometric wavelet theory and used for deinterlacing and upconversion in this application. The algorithms have been developed by a mathematics team at Let it Wave, led by Stéphane Mallat, professor of applied mathematics at Ecole Polytechnique in Paris. How does it work? To illustrate the beneﬁts of the new technology, let’s compare it with current technologies — deinterlacing and scaling. In the 1980s and 1990s, the ﬁrst challenge of deinterlacing was real-time digital video processing at a minimum cost. Minimizing the number of operations and memory requirements was thus necessary, which ﬁrst led to two simple methods: spatial line doubling or time weaving. storage elements. It was not until the application of digital signal processing that standards conversion equipment started to approach anything close to the levels of transparency demanded by the broadcasters — but initially at very signiﬁcant cost. As digital TV production, along with the introduction of HDTV services, started in the 1990s, the requirement them to be purchased in large numbers. And even these expensive devices can exhibit subjectively annoying artifacts on certain types of material, particularly material involving lots of detail and movement at critical velocities. Notwithstanding the performance limitations, price is an increasing issue as the demand for format converters is growing rapidly. In particular, there is 16 broadcastengineeringworld.com | April 2008 http://broadcastengineeringworld.com

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Broadcast Engineering - April 2008 Contents Editorial HD Newsrooms Wavelet Compression Mobile TV Audio Processing for HDTV, Part 1 QoE for IPTV End Users NAB Update Asset Management Advertisers Index

Broadcast Engineering - April 2008

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