Instead of coding values of the sampled waveform in

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P.36A Simple MP3 Encoder Perceptual noise shapingConvert the signal from time domain to frequency domainTime Domain toFrequency DomainConversionPerceptual Noise shaping AnalysisQuantization and Huffman CodingInput music+MP3 music
P.37MPEG – A Family of Audio-Visual Coding StandardMPEG(pronounced M-peg) stands for Moving Picture Experts Group. It is the name of the family of standards used for coding audio-visual information (e.g., movies, video, music) in a digital compressed format. The major advantage of MPEG compared to other video and audio formats is that MPEG files are much smaller for the same quality. This is because MPEG uses very sophisticated compression techniques.MP3 is part of the MPEG standard.
P.38MPEG-2 for Cable TV and DVDMPEG-2is the first popular MPEG standard. It is typically used to encode audio and video for broadcast signals, including direct broadcast satelliteand Cable TV. With some modifications, it is also the coding format used by standard commercial DVD movies andHDTV (High Definition Television).Key techniques used include inter-frame prediction and coding in the frequency domain(Discrete Cosine Transform coding/DCT).In predictive coding, the coder and decoder use an algorithm to predictwhat many intermediate frames should be based on some anchor frames. The coder encodes only the difference between the actual frame and the predicted. If this difference is small most of the time, there is not as information to encode.DCT takes advantage of the fact that most signal energy is at low frequenciesand that there are often many consecutive zero valuesin the amplitudes of adjacent frequency components
P.39MPEG-4 MPEG-4 is a more advanced standard for video and audio compression introduced in late 1998. (HKUST played a key role here!)The MPEG-4 standard is now used in web(streaming media) and CD distribution, conversation(videophone), video-conferenceand broadcast television. MPEG-4 absorbs many of the features of MPEG-2, and adds advanced techniques such as motion estimation – predicting how blocks of pixels will move across the picture in successive frames.Most features included in MPEG-4 are optional and left to individual developersto decide whether to implement them.
P.40Summary – Lecture 14Introduced the Huffman code as an algorithm for symbol-to-codeword assignment. The Huffman code minimizes the average number of bits needed to encode symbols by assigning long codewords to less likely symbols.Huffman works by repeatedly combining the two least likely symbols/sub-treesto form a bigger sub-tree. Huffman is used as part of almost all source coding algorithms, lossless or lossy• Demonstrated entropyas the fundamental limit on the least

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