Method and apparatus for subsampling phase spectrum information

• US 6,678,649 B2
• Filed: 02/01/2002
• Issued: 01/13/2004
• Est. Priority Date: 07/19/1999
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Manjunath, Sharath
• Primary Examiner(s): ABEBE, DANIEL DEMELASH
• Application Number:
  US10/066,073
• Publication Number:
  US 20020095283A1
• Time in Patent Office: 711 Days
• Field of Search: 704/215, 704/220, 704/221, 704/222, 704/500, 704/501, 704/504, 704/207, 704/230
• US Class Current: 704/207
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders
• CPC Class Codes: G10L 19/097 using prototype waveform decomposition or prototype waveform interpolative [PWI] coders
• CPC Class Codes: G10L 25/27 characterised by the analysis technique

Abstract

Method and apparatus for subsampling phase spectrum information by analyzing and reconstructing a prototype of a frame. The prototype is analyzed by correlating phase parameters generated from the prototype with phase parameters generated from a reference prototype in multiple frequency bands. The prototype is reconstructed using linear phase shift values by producing a set of phase parameters of the reference prototype, generating a set of linear phase shift values associated with the prototype, and composing a phase vector from the set of phase parameters and the set of linear phase shift values across multiple frequency bands. The prototype is reconstructed using circular rotation values by producing a set of circular rotation values associated with the prototype, generating a set of bandpass waveforms associated with the phase parameters of the reference prototype in multiple frequency bands, and modifying the set of bandpass waveforms based upon the circular rotation values.

Claims

1. A speech coder, comprising:

a prototype extractor configured to extract a current prototype from a current frame being processed by the speech coder; and

a prototype quantizer coupled to the prototype extractor and configured to produce a plurality of phase parameters of a reference prototype of a frame, generate a plurality of linear phase shift values associated with the current prototype, and compose a phase vector from the phase parameters and the linear phase shift values across a plurality of frequency bands, wherein the prototype quantizer is further configured to unquantize a plurality of quantized phase parameters associated with the current prototype to generate the plurality of linear phase shift values.

2. The speech coder of claim 1, wherein the prototype quantizer is further configured to compute discrete Fourier series coefficients for the reference prototype and decompose the discrete Fourier series coefficients into amplitude vectors and phase vectors for the reference prototype.

3. The speech coder of claim 1, wherein the prototype quantizer is further configured to identify the plurality of frequency bands.

4. The speech coder of claim 1, wherein the current frame is a speech frame.

5. The speech coder of claim 1, wherein the current frame is a frame of linear prediction residue.

6. The speech coder of claim 3, wherein the prototype quantizer is further configured to further unquantize a plurality of amplitude quantization parameters associated with the current prototype to produce a plurality of unquantized amplitude parameters, and to identify the plurality of bands based upon the plurality of unquantized amplitude parameters.