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A MFCC-Based CELP Speech Coder for Server-Based Speech Recognition in Network Environments Jae Sam YOON Gil Ho LEE Hong Kook KIM Publication IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences Vol.E90-A No.3 pp.626-632 Publication Date: 2007/03/01 Online ISSN: 1745-1337 DOI: 10.1093/ietfec/e90-a.3.626 Print ISSN: 0916-8508 Type of Manuscript: Special Section PAPER (Special Section on Multimedia and Mobile Signal Processing) Category: Speech/Audio Processing Keyword: MFCC-based coder, server-based speech recognition, speech coding, safety-net PVQ, Full Text: PDF(440.4KB)>>
Summary: Existing standard speech coders can provide high quality speech communication. However, they tend to degrade the performance of automatic speech recognition (ASR) systems that use the reconstructed speech. The main cause of the degradation is in that the linear predictive coefficients (LPCs), which are typical spectral envelope parameters in speech coding, are optimized to speech quality rather than to the performance of speech recognition. In this paper, we propose a speech coder using mel-frequency cepstral coefficients (MFCCs) instead of LPCs to improve the performance of a server-based speech recognition system in network environments. To develop the proposed speech coder with a low-bit rate, we first explore the interframe correlation of MFCCs, which results in the predictive quantization of MFCC. Second, a safety-net scheme is proposed to make the MFCC-based speech coder robust to channel errors. As a result, we propose an 8.7 kbps MFCC-based CELP coder. It is shown that the proposed speech coder has a comparable speech quality to 8 kbps G.729 and the ASR system using the proposed speech coder gives the relative word error rate reduction by 6.8% as compared to the ASR system using G.729 on a large vocabulary task (AURORA4). | ||||||||||
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