[工学]LectureNotes3.pdfVIP

Principal Multimedia Signal Processing Techniques Prof. Lu Yu Institute of Information and Communication Engineering Zhejiang University 2005. 9 Multimedia Communication Outline of multimedia processing techniques Compression Watermaking Organization, storage and retrieval Multimedia processor Multimedia Communication Yu, Lu, 2005 2 Outline of compression Entropy coding Prediction coding Inter frame Intra frame Transform DCT Transform integer transform Hybrid coding Multimedia Communication Yu, Lu, 2005 3 Entropy of a Memoryless Source Let a memoryless source be characterized by an ensemble U0 with: Alphabet { a 0 ,a 1 ,a 2 , ... ,a K-1 } Probabilities { P(a 0 ), P(a 1 ), P(a 2 ), ..., P(a K-1 )} Shannon: information conveyed by message “a ” k I(a k ) = -log(P(a k )) “Entropy of the source” is the average information contents: H(U 0 ) = E{I(a k )} = -P(a k )*log (P(a k )) For „log“ = „log 2 “ the unit is bits/symbol Multimedia Communication Yu, Lu, 2005 4 Entropy and Bit-Rate Properties of entropy: H(U 0 ) = 0 max { H(U 0 )}=logK with P(a j )=P(a k ) for all j, k The entropy H(U 0 ) is a lower bound for the average word length l av of a decodable variable length code