LSF coefficient vector quantizer for wideband speech coding

• US 20040176951A1
• Filed: 12/30/2003
• Published: 09/09/2004
• Est. Priority Date: 03/05/2003
• Status: Abandoned Application

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Kang, Sang Won, Lee, Kang Eun, Sung, Ho Sang, Hwang, Dae Hwan
• Application Number:
  US10/749,745
• Publication Number:
  US 20040176951A1
• Time in Patent Office: Days
• US Class Current: 704/222
• CPC Class Codes: G10L 19/07 Line spectrum pair [LSP] vocoders

Abstract

A line spectral frequency (LSF) coefficient vector quantizer greatly affects wideband speech coding efficiency and performance. An LSF coefficient quantizer of an existing speech codec can be modified into a new structure in which a non-structural vector quantizer and a lattice quantizer are connected in series. Thus, memory capacity and search time required for the LSF coefficient quantizer can be reduced. In addition, a prediction structure and a non-prediction structure can be connected in parallel to stably perform quantization and reduce a quantization transfer error. As a result, an efficient LSF quantizer capable of reducing allocated bits and improving SD can be provided. Moreover, non-structural vector quantization can be performed prior to pyramid vector quantization to convert an input value into a Laplacian model suitable for a pyramid vector quantizer. Also, a high-performance quantizer can be provided by determining a joint optimisation vector between two serial quantizers using a small amount of computation of the pyramid vector quantizer. Furthermore, outliers unsuitable for the prediction structure can be correctly quantized by adopting the prediction structure and the non-prediction structure.

Claims

1. A line spectral frequency coefficient vector quantizer comprising:

a prediction structure quantizer that comprises a first vector quantizer which non-structurally quantizes a line spectral frequency coefficient vector to calculate a candidate vector to be quantized, a predictor which calculates a predicted line spectral frequency vector of the line spectral frequency coefficient vector, and a first lattice quantizer which lattice-quantizes the candidate vector with reference to the predicted line spectral frequency vector to calculate a final prediction quantization vector of the line spectral frequency coefficient vector;

a non-prediction structure quantizer that comprises a second vector quantizer which non-structurally quantizes the line spectral frequency coefficient vector to calculate a candidate vector to be quantized and a second lattice quantizer which lattice-quantizes the candidate vector to calculate a final non-prediction quantization vector of the line spectral frequency coefficient vector; and

a switch that determines one having a small difference from the line spectral frequency coefficient vector, from the final prediction quantization vector and the final non-prediction quantization vector, as a final quantization vector of the line spectral frequency coefficient vector.

2. The line spectral frequency coefficient vector quantizer of claim 1, wherein the prediction structure quantizer and the non-prediction structure quantizer are connected in parallel to quantize the line spectral frequency coefficient vector.

3. The line spectral frequency coefficient vector quantizer of claim 1 or 2, wherein the first vector quantizer and the first lattice quantizer are connected in series to quantize the line spectral frequency coefficient vector.

4. The line spectral frequency coefficient vector quantizer of claim 1 or 2, wherein the second vector quantizer and the second lattice quantizer are connected in series to quantize the line spectral frequency coefficient vector.

5. The line spectral frequency coefficient vector quantizer of claim 1, wherein the first lattice quantizer is a pyramid vector quantizer.

6. The line spectral frequency coefficient vector quantizer of claim 1, wherein the second lattice quantizer is a pyramid vector quantizer.