Gain quantization for a CELP speech coder
View Patent ↗There is provided a speech encoding system that receives a speech signal. The speech encoding system comprises a frame processor for processing a frame of the speech signal, where the frame processor includes a pitch gain generator that derives unquantized pitch gains, and a first vector guantizer that receives the unquantized pitch gains and generates quantized pitch gains. The speech encoding system also comprises a subframe processor that begins subframe processing after the pitch gain generator has derived the unquantized pitch gains and the first vector quantizer has generated the quantized pitch gains.
1. A speech encoding system that receives an input speech signal, the speech encoding system comprising:
a frame processor for processing a frame of the input speech signal, the frame processor including:
a pitch gain generator that derives unquantized pitch gains; and
a first vector quantizer that receives the unquantized pitch gains and generates quantized pitch gains;
a subframe processor that is configured to begin subframe processing after the pitch gain generator has derived the unquantized pitch gains and the first vector quantizer has generated the quantized pitch gains; and
wherein the speech encoding system is configured to convert the input speech signal into an encoded speech using results from the frame processor and the subframe processor.
2. The speech encoding system of claim 1 further comprising:
a periodic signal detector that determines whether the speech signal is periodic or non-periodic;
wherein the frame processor allocates less bits for coding the frame if the periodic signal detector determines that the speech signal is periodic than if the periodic signal detector determines that the speech signal is non-periodic.
3. The speech encoding system of claim 1 , wherein the subframe processor includes a closed-loop generator that generates unquantized fixed codebook gains, and wherein the speech encoding system further comprises a second vector quantizer that receives the unquantized fixed codebook gains and generates quantized fixed codebook gains in a delayed decision closed-loop after subframe processing by the subframe processor.
4. The speech encoding system of claim 3 further comprising:
a first codebook that generates an adaptive codebook excitation vector;
a first multiplier that multiplies the adaptive codebook excitation vector with the quantized pitch gain to produce a scaled adaptive codebook gain vector;
a second codebook that generates a fixed codebook excitation vector;
a second multiplier that multiplies the fixed codebook excitation vector with the fixed codebook gain to produce a scaled fixed codebook gain vector;
an adder that adds the scaled adaptive codebook gain vector with the scaled fixed codebook gain vector.
5. The speech encoding system of claim 3 further comprising a third vector quantizer that performs a joint vector quantization of the adaptive codebook gains and the fixed codebook gains in a closed loop.
6. A method for use in a speech encoding system that receives an input speech signal, the method comprising:
processing a frame of the input speech signal using a frame processor by:
deriving unquantized pitch gains using a pitch gain generator; and
receiving the unquantized pitch gains by a first vector quantizer and generating quantized pitch gains;
beginning subframe processing using a subframe processor after the pitch gain generator has derived the unquantized pitch gains and the first vector quantizer has generated the quantized pitch gains; and
converting the input speech signal into an encoded speech using results from the frame processor and the subframe processor.
7. The method of claim 6 further comprising:
determining whether the speech signal is periodic or non-periodic using a periodic signal detector;
wherein the frame processor allocates less bits for coding the frame if the periodic signal detector determines that the speech signal is periodic than if the periodic signal detector determines that the speech signal is non-periodic.
8. The method of claim 6 , wherein the subframe processor includes a closed-loop generator that generates unquantized fixed codebook gains, and wherein the speech encoding system further comprises a second vector quantizer that receives the unquantized fixed codebook gains and generates quantized fixed codebook gains in a delayed decision closed-loop after subframe processing by the subframe processor.
9. The method of claim 8 further comprising:
generating an adaptive codebook excitation vector using a first codebook;
multiplying the adaptive codebook excitation vector with the quantized pitch gain to produce a scaled adaptive codebook gain vector;
generating a fixed codebook excitation vector using a second codebook;
multiplying the fixed codebook excitation vector with the fixed codebook gain to produce a scaled fixed codebook gain vector;
adding the scaled adaptive codebook gain vector with the scaled fixed codebook gain vector.
10. The method of claim 8 further comprising performing a joint vector quantization of the adaptive codebook gains and the fixed codebook gains in a closed loop.