Sound Encoder And Sound Encoding Method

• US 20080091440A1
• Filed: 10/25/2005
• Published: 04/17/2008
• Est. Priority Date: 10/27/2004
• Status: Active Grant

• Current Assignee: III Holdings 12, LLC (Intellectual Ventures LLC)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Oshikiri, Masahiro
• Granted Patent: US 8,099,275 B2
• Time in Patent Office: Days
• US Class Current: 704/501
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders

Abstract

A sound encoder having an improved quantization performance while suppressing an increase of the bit rate to a lowest level. In a second layer encoding unit (40), a standard deviation calculating section (408) calculates the standard deviation &sgr;c of a first layer decoding spectrum after decoding scale factor ratio multiplication and outputs the standard deviation &sgr;c to a selecting section (409), the selecting section (409) selects a linear transform function as the function for nonlinear transform of the residual spectrum according to the standard deviation &sgr;c, a nonlinear transform function section (410) selects one of prepared nonlinear transform functions #1 to #N according to the result of the selection by the selecting section (409) and outputs the selected one to an inverse transform section (411), and the inverse transform section (411) subjects inverse transform (expansion) to a residual spectrum candidate stored in a residual spectrum code book (412) using the nonlinear transform function outputted from the nonlinear transform function section (410) and outputs the result to an adder (413).

Claims

1. A speech coding apparatus that performs encoding having a layered structure composed of a plurality of layers, the speech coding apparatus comprising:

an analysis section that analyzes spectrum of a decoded signal of a lower layer to calculate a decoded spectrum of the lower layer;

a selection section that selects one nonlinear transform function among a plurality of nonlinear transform functions based on a degree of variation of the decoded spectrum of the lower layer;

an inverse transform section that inverse transforms a nonlinear transformed residual spectrum using the nonlinear transform function selected by the selection section; and

an addition section that adds the inverse transformed residual spectrum to the decoded spectrum of the lower layer to obtain a decoded spectrum of an upper layer.

2. The speech coding apparatus according to claim 1, further comprising a plurality of residual spectrum codebooks corresponding to the plurality of nonlinear transform functions.

3. The speech coding apparatus according to claim 1, wherein the selection section selects, for each of a plurality of subbands, one nonlinear transform function among a plurality of nonlinear transform functions provided to each of the plurality of subbands.

4. The speech coding apparatus according to claim 1, wherein the selection section selects one nonlinear transform function among the plurality of nonlinear transform functions according to a degree of variation of an error spectrum that is estimated from the degree of variation of the decoded spectrum of the lower layer.

5. The speech coding apparatus according to claim 4, wherein the selection section further encodes information indicating the degree of variation of the error spectrum.

6. A radio communication mobile station apparatus comprising the speech coding apparatus according to claim 1.

7. A radio communication base station apparatus comprising the speech coding apparatus according to claim 1.

8. A speech coding method of performing encoding having a layered structure composed of a plurality of layers, the speech coding method comprising:

an analysis step of analyzing spectrum of a decoded signal of a lower layer to calculate a decoded spectrum of the lower layer;

a selection step of selecting one nonlinear transform function among a plurality of nonlinear transform functions based on a degree of variation of the decoded spectrum of the lower layer;

an inverse transform step of inverse transforming a nonlinearly transformed residual spectrum using the nonlinear transform function selected in the selection step; and

an addition step of adding the inverse transformed residual spectrum to the decoded spectrum of the lower layer to obtain a decoded spectrum of an upper layer.