Apparatus for quantizing spectral envelope including error selector for selecting a codebook index of a quantized LSF having a smaller error value and method therefor

• US 6,275,796 B1
• Filed: 04/15/1998
• Issued: 08/14/2001
• Est. Priority Date: 04/23/1997
• Status: Expired due to Fees

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Moo-young, Cho, Yong-duk, Kim, Hong-kook
• Primary Examiner(s): Zele, Krista
• Assistant Examiner(s): Opsasnick, Michael N.
• Application Number:
  US09/060,345
• Time in Patent Office: 1,217 Days
• Field of Search: 704/219, 704/226, 704/230
• US Class Current: 704/230
• CPC Class Codes: G10L 19/07 Line spectrum pair [LSP] vocoders

Abstract

An apparatus for quantizing a spectral envelope with noise robustness showing high performance even under a background noise environment and a channel noise environment, and a method therefor, are provided. The spectral envelope quantizing apparatus includes a spectral envelope quantizing apparatus with noise robustness for representing a spectral envelope of speech by a minimum number of bits for the optimal coding of a speech signal. The apparatus includes a line spectrum frequencies (LSFs) input portion for converting linear predictive coding coefficients extracted from the speech into Nth order line spectrum frequencies coefficients and inputting the coefficients as the LSFs of a current frame. It also includes a linked split-vector quantizing portion for dividing the LSFs into a predetermined number of linked sub-vectors and quantizing the sub-vectors, and a predictive linked split-vector quantizing portion for obtaining the difference between the LSFs and the LSFs of a previous frame and vector-quantizing the difference. The apparatus further includes an error selector for comparing the error values of the LSFs quantized in the linked split-vector quantizing portion and the predictive linked split-vector quantizing portion, selecting the codebook index of the quantized LSFs having the smaller error value, and outputting the selected codebook index together with a mode bit.

Claims

1. A spectral envelope quantizing apparatus with noise robustness for representing a spectral envelope of speech by a minimum number of bits for the optimal coding of a speech signal, comprising:

a line spectrum frequencies (LSFS) input portion for converting linear predictive coding coefficients extracted from the speech into Nth order line spectrum frequencies coefficients and inputting the coefficients as the LSFs of a current frame;

a linked split-vector quantizing portion for dividing the LSFs into a predetermined number of linked sub-vectors and quantizing the sub-vectors;

a predictive linked split-vector quantizing portion for obtaining the difference between the LSFs of a current frame and the LSFs of a previous frame and vector-quantizing the difference; and

an error selector for comparing the error values of the LSFs quantized in the linked split-vector quantizing portion and the predictive linked split-vector quantizing portion, selecting the codebook index of the quantized LSFs having the smaller error value, and outputting the selected codebook index together with a mode bit.

2. The spectral envelope quantizing apparatus of claim 1, further comprising:

a line spectrum frequency decoder for receiving the codebook index and the mode bit and decoding the quantized LSFs;

a multiplication controller for multiplying the LSFs decoded in the line spectrum frequency decoder by predetermined predictive coefficients; and

a signal delayer for storing the value multiplied by the multiplication controller, delaying the value by the input time of a frame, and outputting the value to the predictive linked split-vector quantizing portion.

3. A spectral envelope quantizing method with noise robustness for representing a spectral envelope of speech by a minimum number of bits for the optimal coding of a speech signal, comprising the steps of:

inputting the LSFs of a current frame;

dividing the LSFs into a predetermined number of linked sub-vectors and linked split-vector-quantizing the sub-vectors and, at the same time, obtaining the difference between the LSFs and the LSFs of a previous frame and predictive linked split-vector-quantizing the difference;

comparing the error values of the linked split-vector quantized LSFs with those of the predictive split-vector quantized LSFs; and

selecting the codebook index of the quantized LSFs having the smaller error value and outputting the selected codebook index together with a mode bit.

4. The method of claim 3, further comprising the steps of:

receiving the codebook index and the mode bit and decoding the quantized LSFs;

multiplying the decoded LSFs by predetermined prediction coefficients;

storing the multiplied value for the predictive linked split-vector quantization of the next frame; and

delaying the stored value by the input time of a frame until the LSFs of the next frame are input.

5. A spectral envelope quantizing apparatus with noise robustness for representing a spectral envelope of speech by a minimum number of bits for the optimal coding of a speech signal, comprising:

an LSFs input portion for converting linear predictive coding coefficients extracted from the speech into Nth order LSF coefficients and inputting the coefficients as the LSFs of a current frame;

a clean environment quantizing portion for dividing the LSFs into a predetermined number of linked sub-vectors and vector-quantizing the sub-vectors under a clean speech environment;

a babble noise quantizing portion for dividing the LSFs into the predetermined number of linked sub-vectors and vector-quantizing the sub-vectors under a babble noise environment;

a car noise quantizing portion for dividing the LSFs into the predetermined number of linked sub-vectors and vector-quantizing the sub-vectors under a car noise environment;

a predictive linked split-vector quantizing portion for obtaining the difference between the LSFs and the LSFs of a previous frame and vector-quantizing the difference under all the environments; and

an error selector for comparing the error values of the LSFs quantized in the clean environment quantizing portion, the babble noise quantizing portion, the car noise quantizing portion, and the predictive linked split-vector quantizing portion to each other, selecting the codebook index of the quantized LSF having the smallest error value, and outputting the selected codebook index together with a mode bit.

6. The spectral envelope quantizing apparatus of claim 5, further comprising:

an LSF decoder for receiving the codebook index and the mode bit and decoding the quantized LSFs;

a multiplication controller for multiplying the LSFs decoded in the LSF decoder by predetermined prediction coefficients; and

a signal delayer for storing the value multiplied by the multiplication controller, delaying the value by the input time of one frame, and outputting the value to the predictive linked split-vector quantizing portion.

7. A spectral envelope quantizing method with noise robustness for representing the spectral envelope of speech by a minimum number of bits for the optimal coding of a speech signal, comprising the steps of:

inputting the LSFs of a current frame;

dividing the LSFs into a predetermined number of linked sub-vectors and linked split-vector-quantizing the sub-vectors through codebooks trained under a clean speech environment, a babble noise environment, and a car noise environment and, at the same time, obtaining a difference between the LSFs and the LSFs of a previous frame through codebooks trained under all the circumstances and predictive split-vector-quantizing the sub-vectors;

comparing the error values of the linked split-vector quantized LSFs with those of the predictive split-vector quantized LSFs; and

selecting the codebook index of the quantized LSF having the smallest error value and outputting the selected codebook index together with a mode bit.

8. The method of claim 7, further comprising the steps of:

receiving the codebook index and the mode bit and decoding the quantized LSF;

multiplying the decoded LSFs by a predetermined prediction coefficient;

storing the multiplied value for the predictive linked split-vector quantization of the next frame; and

delaying the stored value by the input time of one frame until the LSFs of the next frame are input.