Abstract: A speech encoder, decoder, system, method, and machine-readable software which determine whether to enhance the quantization of speech modeling information depending on the change of one or more identified parameters. An encoder outputs a base quantization value that represents a communication signal information quantized at a base quantization level or sends an enhanced quantization value that represents communitcation signal information quantization level higher than the base quantization level.

Abstract: A fixed codebook response is able to better characterize an input signal of a vocoder because the entries of the fixed codebook are tailored to the input signal being processed. A uniformly distributed random noise signal is stored in a transmitting vocoder. During encoding by the transmitting vocoder, the noise signal is shaped by a weighing filter and a pitch sharpening filter, which are condition controlled by the linear predictive coding, pitch and pitch gain characteristics of the input signal being encoded. The shaped noise signal is passed though a thresholding filter to arrive at a pulse sequence having a given sparcity. The fixed codebook response is chosen as that portion of the pulse sequence which best matches a residual signal of the input signal. The indexed location of that portion along the pulse sequence is designated as the fixed codebook bits which are included within the bit frame. The identical random noise signal is stored in a receiving vocoder.