High quality low bit rate celp-based speech codec

Details High quality low bit rate celp-based speech codec High quality low bit rate celp-based speech codec

1992-06-25

1996-02-27

Knepper, David D.

395 217, 395 232, 395 228, 395 22, G10L 302

Patent

active

054955556

ABSTRACT:
Code excited linear prediction (CELP) is performed using two voiced and unvoiced sets of windows, each set is used both for linear prediction and pitch determination. The accompanying degradation in voice quality is comparable to the IS54 standard 8.0 Kbps voice coder employed in U.S. digital cellular systems. This is accomplished by using the same parametric model used in traditional CELP coders but determining, quantizing, encoding, and updating these parameters differently. The low bit rate speech decoder is like most CELP decoders except that it operates in two modes depending on the received mode bit. Both pitch prefiltering and global postfiltering are employed for enhancement of the synthesized speech. In addition, built-in error detection and error recovery schemes are used that help mitigate the effects of any uncorrectable transmission errors.

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A High-Quality Multirate Real-Time CELP Coder by Peter Kroon and Kumar Swaminathan, IEEE Journal on Selected Areas in Communications, vol. 10, No. 5, Jun. 1992.
Shihua Wang and Allen Gersho, "Improved Phonetically-Segmented Vector Excitation Coding at 3.4 KB/S," Mar. 23, 1992 IEEE, I-349 to I-352.

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