| 摘要 |
A method, system and program for encoding speech. The method comprises receiving an input signal representing a property of speech, quantizing the input signal, thus generating a quantized output signal, prior to the quantization, supplying a version of the input signal to a first noise shaping filter having a first set of filter coefficients, thus generating a first filtered signal based on that version of the input signal and the first set of filter coefficients. Following the quantization, supplying a version of the quantized output signal to a second noise shaping filter having a second set of filter coefficients different than said first set, thus generating a second filter signal based on that version of the quantized output signal and the second set of filter coefficients, performing a noise shaping operation to control a frequency spectrum of a noise effect in the quantized output signal caused by the quantization, wherein the noise shaping operation is performed based on both the first and second filtered signal and transmitting the quantized output signal in an encoded signal. The invention overcomes the problem of coding inefficiencies and noise by applying one filter to a signal before quantization and another with different filter coefficients to a signal after quantization. Therefore, the signal spectrum and coding noise spectrums are manipulated separately. |
