We propose a wideband CELP-type speech coder at 16 kb/s based on a mel-generalized cepstral (MGC) analysis technique. MGC analysis makes it possible to obtain a more accurate representation of spectral zeros compared to linear predictive (LP) analysis and take a perceptual frequency scale into account. A major advantage of the proposed coder is that the benefits of MGC representation of speech spectra can be incorporated into the CELP coding process. Subjective tests show that the proposed coder at 16 kb/s achieves a significant improvement in performance over a 16 kb/s conventional CELP coder under the same coding framework and bit allocation. Moreover, the proposed coder is found to outperform the ITU-T G.722 standard at 64 kb/s. key words: wideband speech coding, mel-generalized cepstral analysis, mel-generalized cepstrum, CELP coding

Wideband CELP coder at 16-kbit/s with 10-ms frame.

A 16kb/s Wideband CELP-Based Speech Coder Using Mel-Generalized Cepstral Analysis

Processing of LPC Cepstrum for Speech Coding

This paper proposes a design for an ISO/IEC MPEG-4 general audio encoder to improve the speech quality at low bit rates. The main contributions to the improvement are using i) a higher sampling rate to get higher time resolution for a given frame length and ii) adaptive preprocessing to reduce the bandwidth. Listening tests at 8 and 16 kbit/s showed that compared with a conventional audio coder and a speech-specific coder, the proposed coder provided better speech quality than the conventional audio coder (MP3) while keeping the quality for music. For speech signals, however, the speech-specific coder (MPEG-4 CELP) produced significantly better quality than the audio coders. The proposed design will be especially useful for low-bit-rate audio-visual delivery applications which may include both speech and music signals.

Wideband CELP coder at 16-kbit/s with 10-ms frame.

Citations

A 16kb/s Wideband CELP-Based Speech Coder Using Mel-Generalized Cepstral Analysis

Processing of LPC Cepstrum for Speech Coding

Design of an MPEG-4 general audio coder for improving speech quality

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