| Summary: | 碩士 === 國立交通大學 === 電子工程系所 === 93 === In this thesis, based on the SNR-scalability scheme in MPEG-4, we propose a flexible approach, which can separately enhance the video quality for different frequency bands. We call this capability “Frequency Information Selection (FIS).” An architecture that provides FIS is also developed. In this architecture, we segment the DCT coefficients into different bands before bit-plane coding so that there is independent SNR-scalability in each frequency band. Then we properly design the entropy codes for each band to improve coding efficiency. Based on human visual perception, we design some experiments to help decide the proper mechanism for the enhancement of visual quality at a given bit-rate. On the other hand, based on the proposed architecture “spatial scalability” is achievable after some proper adjustment at the decoder side. Decoders of different spatial resolutions may receive data up to different frequency bands, scale the DCT coefficients properly, perform the IDCT transform of different sizes, and finally rebuild frames of different sizes. The motion vectors are also scaled down accordingly to perform motion compensation in frames of different sizes.
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