What are the scaleable modes of MPEG-2?
A. Scaleable video is permitted only in the High Profiles. Currently, there are four scaleable modes in the MPEG-2 toolkit. These modes break MPEG-2 video into different layers (base, middle, and high layers) mostly for purposes of prioritizing video data. For example, the high priority channel (bitstream) can be coded with a combination of extra error correction information and/or increased signal strength (i.e. higher Carrier- to-Noise ratio or lower Bit Error Rate) than the lower priority channel. For example, in HDTV, the high priority bitstream (720 x 480) can be decoded under noise conditions were the lower priority (1440 x 960) cannot. This is part of the “graceful degradation concept. Breaking a video signal into two streams (base and enhancements) has a penalty, however. Usually less than 1.5 dB. Another purpose of salability is complexity division. A standard TV set need only decode the 720 x 480 channel, thus requiring a less expensive decoder processor than a TV set wishing
Related Questions
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