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Examine issues of HD apps

Posted: 18 Dec 2006 ?? ?Print Version ?Bookmark and Share

Keywords:HD implementation? HD vs. SD? HD video implementation tips? high definition transition? Jeremiah Golston?

High-definition (HD) video development is heating up, fueled by the availability of better display and storage technology. Recent advances have enabled new video capabilities in equipment, ranging in size from cellphones and MP3 players right up to video walls and billboards. Video system designers, lured by the promise of wider screens and higher resolution, must now fully investigate the issues of implementing HD.

It's important to understand what HD involves, since a variety of display formats can be called HD, and some or all of them may be inappropriate in certain applications. TV, with its new digital formats, is an important application, but every type of display is a potential target for upgraded technology. The real question for the developer is not so much whether HD is required, but how to achieve the best possible quality, given the system's display, bandwidth, and storage and cost constraints.

Any changeover in technology involves issues that may not be immediately apparent to system developers. Here are a few do's and don'ts to remember as you undertake the transition to HD.

Do

  • Be aware of the greater system requirements of the HD format. Decompressed 1080i60 video has six times the data of decompressed standard-definition (SD) video. So in raw terms, the system has to provide 6x the processing throughput and memory. Also, the advanced codecs that support HD achieve greater compression by using more memory, I/O bandwidth and processing, pushing system requirements further.

  • Focus on audio and video, since they figure just as highly in perceived quality.

  • Consider the display size. HD is only effective with displays measuring 40inches or more diagonally. With smaller displays, viewers can't tell the difference between HD and SD. Compression algorithms are lossy, so the decompressed image is less well-defined than the original.

  • Realize that programmability allows the system to be scaled and redesigned to meet requirements for different regions and markets.

  • Keep in mind that it is important to be able to interoperate with legacy systems. Systems that exchange video within home networks will increasingly require transcoding among standards.

  • Analyze the trade-offs in quality, bandwidth and cost. An SoC using DSP can offset some of the cost with the right combination of flexibility, optimized video peripherals and acceleration. Processors that integrate DSP and RISC cores can partition performance. Programmability provides versatility and scalability for system implementation, and comprehensive software platforms, with A/V APIs and standard codec algorithms, can speed development.

Don't

  • Assume that digital video is the same as HD video. The general public may be a bit confused about the difference between HDTV and DTV, but the entire spectrum of digital video applications is enormous, and HD is only a portion of it.

  • Consider only one format. HD encompasses a range of display resolutions.

  • Underestimate market complexity when choosing a processor. All of the ITU/MPEG standards offer variations in implementation, and the changeover from MPEG-2 to H.264/MPEG-4 AVC codecs will be significant in the next few years. Competing standards such as WMV9/VC-1 and China's Audio Video Standard will also claim their share of applications. Systems such as STBs may have to deal dynamically with any number of standards and variations, as well as interface to entertainment and gaming consoles, and transcode and transrate video for home computer networks.

  • Forget that system integration is lowering the cost of HD rapidly. Thus, a system that is not cost-effective today may be so in the next generation. The system developer has to decide whether to support HD now at today's higher cost, or stay with SD for a year or two until HD component costs are lower and HD demand has increased.

  • Let HD hype make system decisions for you. HD is not required for all applications. The real question is how to achieve the best possible video quality for the target display, within system bandwidth and storage constraints and that ever-present factor: cost.

    - Jeremiah Golston
    Chief Technology Officer, Streaming Media Division

    - Gene Franz
    Principal Fellow Texas Instruments Inc.




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