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Evaluation criteria for high-definition video

Posted: 08 Jan 2007 ?? ?Print Version ?Bookmark and Share

Keywords:HD video? high-definition video standard? digital TVs? digital TV? standard-definition video?

By Jeremiah Golston and Gene Frantz
Texas Instruments Inc.

High-definition video development is heating up, fueled by the availability of better display and storage technology and by the looming deadline for digital TV transmission in North America.

Recent advances have enabled new video capabilities in equipment ranging from cellphones and MP3 players to video walls and billboards. Thus, manufacturers are now looking to introduce HD capability in many applications where standard-definition (SD) video was previously acceptable.

In this environment, it is important that the designer understand what HD involves, since a variety of display formats can be called high definition, and some or all of them may be inappropriate in certain applications. The real question for the developer is not so much whether HD is required, but how to achieve the best possible quality for the system in question, given its display, bandwidth and storage constraints-and, of course, how much people will pay for it.

Any changeover in technology involves issues that may not be immediately apparent to system developers. To help you work through such issues, here are a few points to remember as you undertake the transition to HD:

? Be aware of the greater system requirements of the HD format. Decompressed 1080i60 video (1,920 x 1,080 at 60 frames/second interlaced) has six times the data of decompressed SD video, so in raw terms the system has to provide six times the processing throughput and memory. Also, the more advanced codecs that support HD resolution achieve greater compression by employing more memory, I/O bandwidth and processing.
? Focus on audio as well as video, since sound contributes as much as images to the perceived quality.
? Consider your system's display size first. HD is only effective with displays measuring 40 inches or more diagonally; with smaller displays, viewers can't tell the difference between HD and SD.
? Realize that programmability allows the system to be scaled to accommodate new functionality, so the same platform can be readily redesigned to meet requirements for different regions and market segments. Even HD video will soon be transported over IP networks, but the most efficient compression will be required.
? Remember that HD is a relatively new format and should interoperate with legacy systems. Systems that exchange video within home networks will increasingly require transcoding among standards. Flexibility is the key criterion for such transcoding.
? Thoroughly analyze the trade-offs among quality, bandwidth and cost. With HD's huge data throughput and the need to support various codecs and application software, the system may be much more expensive to implement than SD.

? Assume that digital video is the same as HD video. The spectrum of digital video applications is enormous, and HD is only a portion of it.
? Stop at considering only one format. HD encompasses a range of display resolutions (the table shows some of the more-common DTV formats). While most commercial TV broadcasters in North America are implementing 1080i60, other formats may be more advantageous for your application.
? 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 AVS will also claim their share of applications. Set-top boxes 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. High performance and programming flexibility are the keys to addressing the diverse, rapidly evolving video market.
? Forget that system integration is lowering the cost of HD rapidly, so that a system that is not cost-effective today may be cost-effective in the next product generation. The system developer has to consider whether to support HD now, at today's cost, or stay with SD for a year or two until 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 video quality for the target display within the system bandwidth, storage and cost constraints.

About the authors
Jeremiah Golston
is the CTO for Texas Instruments' Streaming Media Division. Comments may be sent to

Gene Frantz is a principal fellow at Texas Instruments. He may reached at

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