Implementation of speech coding technique in MPEG/audio coding

Pao Yue-kong Library Electronic Theses Database

Implementation of speech coding technique in MPEG/audio coding

 

Author: Cheung, Sai-hang
Title: Implementation of speech coding technique in MPEG/audio coding
Degree: M.Sc.
Year: 2000
Subject: Speech processing systems
Coding theory
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Electronic and Information Engineering
Pages: 51 leaves : ill. ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1517721
URI: http://theses.lib.polyu.edu.hk/handle/200/332
Abstract: In multimedia applications such as video transmission and storage, the ISO standard MPEG/audio has been used extensively. This algorithm was developed by the Motion Picture Experts Group (MPEG), as an ISO standard for the high fidelity compression of digital audio. Unlike vocal-tract-model coders specially tuned for speech signals, the MPEG/audio coder gets its compression without making assumptions about the nature of the audio source. Instead, the coder exploits the perceptual limitations of the human ear. Much of the compression results from the removal of perceptually irrelevant limitations of the audio signal. Removal of such parts results in inaudible distortions, thus MPEG/audio can compress any signal meant to be heard by human ear. In addition, for different level of resulting quality, the compressed bitstream can have one of several predefined fixed bit rates ranging from 32 to 192 kbit/sec per channel. While the coding quality of MPEG/audio is satisfactory, there is room to further reduce the bit rate of compressed signal. CELP-based approach has been very successful in telephone bandwidth speech coding, but is not suitable for coding non-speech signals because of the assumed signal production model. Low-delay Code-excited Linear Prediction (LD-CELP) is ITU/CCITT standard G.728 which is a 16 kbit/sec low-delay speech coder. It can achieve a high speech quality better than G.721 with a one-way coding delay less than 2ms. In this project, an approach is proposed to mixed speech/music coding, which uses a discriminator to separate music signals from speech, and codes them with the MPEG/audio coder and a LD-CELP speech coder, respectively. In testing for different audio clips, the system shows promising results.

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