High-quality speech coding at 2.4 to 4.0 kbps based on time-frequency interpolation
ICASSP'93 Proceedings of the 1993 IEEE international conference on Acoustics, speech, and signal processing: speech processing - Volume II
A mixed prototype waveform/CELP coder for sub 3kb/s
ICASSP'93 Proceedings of the 1993 IEEE international conference on Acoustics, speech, and signal processing: speech processing - Volume II
Voiced speech coding at very low bit rates based on forward_backward waveform prediction (FBWP)
ICASSP'93 Proceedings of the 1993 IEEE international conference on Acoustics, speech, and signal processing: speech processing - Volume II
Estimation of the parameters of a long-term model for accurate representation of voiced speech
ICASSP'93 Proceedings of the 1993 IEEE international conference on Acoustics, speech, and signal processing: speech processing - Volume II
Signal transformation and interpolation based on modified DCT synthesis
Digital Signal Processing
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A major source of audible distortion in current low-bit-rate speech coding algorithms is an inaccurate degree of periodicity of the voiced speech signal. If the correlations between neighboring pitch cycles are accurately reproduced, these audible distortions can be reduced significantly. To this purpose, a novel method of coding voiced speech is introduced, which transmits an encoded prototype waveform at 20-30 ms intervals. The prototype waveform describes a pitch cycle representative for the interval, and is quantized using analysis-by-synthesis methods. The speech signal is reconstructed by concatenation of interpolated prototype waveforms. The short-term and the long-term correlations between pitch cycles can be controlled explicitly. Unquantized reconstructed speech is virtually indistinguishable from the original signal. The method results in excellent speech quality at rates between 3.0 and 4.0 kb/s.