CPU制造工艺(3)

Ensuring Quality Output

From the vantage point of professional broadcasting,quality is still one of the biggest issues when evaluatinga software-based approach to encoding. This becomesparticularly important when many media contenttransitions are involved. “Media these days tends to gothrough lots of encoding and decoding and re-encodingbefore it actually hits the TV,” Saint John said. “Thequality at the initial stage of encoding is exceptionallyimportant. When we first launched the MediaRigproduct line last year, we went to great ends to doactual benchmarks based on industry-standard ways ofmeasuring quality.”

The tools that proved extremely useful in this regardwas a product from Sarnoff Corporation calledJNDmetrix*. JNDmetrix (Just Noticeable Difference) isbased on a proprietary model of the human visualsystem that generates metrics for comparing videoquality. JNDmetrix measurements correlate withsubjective judgments of video quality, but they employcomputational techniques to establish quality levels.

The Ligos MPEG-2 codec,capable of transcodingmultiple streams of video on Intel®Xeon processor-based servers for

professional broadcasters,delivers exceptional

performance on the latestgeneration of desktopcomputers equipped withIntel®Pentium®4 processors.Professional

Broadcast Applications

At the high end of the spectrum, Ligos MediaRigtechnology has been successfully implemented atthe professional-broadcast level in the SeaChangeDigital Transcoder.

“SeaChange, which provides video-on-demand andadvertisement-insertion systems for cable multipleservice operators (MSOs), uses the MediaRig system todevelop their own encoder and transcoder products,”Robert Saint John said. “These systems are based onthe MediaRig Core product and are designed andmarketed by SeaChange. The MediaRigCore product isessentially a software development kit and an enginethat system developers use.”

The SeaChange Digital Transcoder, the first MediaRig-based product, takes advantage of the flexibility andscalability of software to provide an automated systemthat seamlessly reformats content from varioussources, and reformats it for delivery matched tochannel and network requirements. Systems are easilyand cost-effectively paired into redundancy groups toensure automatic recovery in the event of a criticalfailure, an important consideration for the broadcastmarket. Time-Warner and Cox Communications cable

“In metrics values compiled with JNDmetrix,” RobertSaint John said, “we were able to consistently meet orexceed the quality of those blackbox-based encodersagainst which we are competing directly. We’vecontinued to make advances in the software on theexact same platforms that we were using last year bymaking updates in the software—just by means ofoptimizations and improvements. We’re actually startingto step up the ladder to compete with encoders thatcost much more than standard $15,000 encoders—encoders that are focused on the cable and satellitemarket. In this market, each channel only getssomewhere between two and three megabits, but thecontent has to look just as good as a DVD, using only athird of the bit rate. Broadcasters pay dearly for flexiblealgorithm functionality, such as noise reduction,temporal filtering, and so on. Those are things that weare implementing and optimizing completely in softwareas we step up the attack on those blackbox models wecompare most favorably against.”

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