Speech classification and parameter weighting used in...

Details Speech classification and parameter weighting used in... Speech classification and parameter weighting used in...

1998-09-18

2002-12-10

Banks-Harold, Marsha D. (Department: 2654)

Data processing: speech signal processing, linguistics, language

Speech signal processing

For storage or transmission

C704S220000, C704S225000

Reexamination Certificate

active

06493665

ABSTRACT:

INCORPORATION BY REFERENCE
The following applications are hereby incorporated herein by reference in their entirety and made part of the present application:
1) U.S. Provisional Application Ser. No. 60/097,569, entitled “Adaptive Rate Speech Codec” filed Aug. 24, 1998;
2) U.S. patent application Ser. No. 09/154,675, entitled “Speech Encoder Using Continuous Warping In Long Term Preprocessing,” filed Sep. 18, 1998;
3) U.S. patent application Ser. No. 09/156,814, entitled “Completed Fixed Codebook For Speech Encoder,” filed Sep. 18, 1998;
4) U.S. patent application Ser. No. 09/156,649, entitled “Comb Codebook Structure,” filed Sep. 18, 1998;
5) U.S. patent application Ser. No. 09/156,648, entitled “Low Complexity Random Codebook Structure,” filed Sep. 18, 1998;
6) U.S. patent application Ser. No. 09/156,650, entitled “Speech Encoder Using Gain Normalization That Combines Open And Closed Loop Gains,” filed Sep. 18, 1998;
7) U.S. patent application Ser. No. 09/156,832, entitled “Speech Encoder Using Voice Activity Detection In Coding Noise,” filed Sep. 18, 1998;
8) U.S. patent application Ser. No. 09/154,654, entitled “Pitch Determination Using Speech Classification And Prior Pitch Estimation,” filed Sep. 18, 1998;
9) U.S. patent application Ser. No. 09/154,657, entitled “Speech Encoder Using A Classifier For Smoothing Noise Coding,” filed Sep. 18, 1998;
10) U.S. patent application Ser. No. 09/156,826, entitled “Adaptive Tilt Compensation For Synthesized Speech Residual,” filed Sep. 18, 1998;
11) U.S. patent application Ser. No. 09/154,653, entitled “Synchronized Encoder-Decoder Frame Concealment Using Speech Coding Parameters,” filed Sep. 18, 1998;
12) U.S. patent application Ser. No. 09/154,663, entitled “Adaptive Gain Reduction To Produce Fixed Codebook Target Signal,” filed Sep. 18, 1998;
13) U.S. patent application Ser. No. 09/154,660, entitled “Speech Encoder Adaptively Applying Pitch Long-Term Prediction and Pitch Preprocessing With Continuous Warping,” filed Sep. 18, 1998.
MICROFICHE REFERENCE
A microfiche appendix B is included of a computer program listing. The total number of microfiche is 1. The total number of frames is 24.
BACKGROUND
1. Technical Field
The present invention relates generally to speech encoding and decoding in voice communication systems; and, more particularly, it relates to various techniques used with code-excited linear prediction coding to obtain high quality speech reproduction through a limited bit rate communication channel.
2. Related Art
Signal modeling and parameter estimation play significant roles in communicating voice information with limited bandwidth constraints. To model basic speech sounds, speech signals are sampled as a discrete waveform to be digitally processed. In one type of signal coding technique called LPC (linear predictive coding), the signal value at any particular time index is modeled as a linear function of previous values. A subsequent signal is thus linearly predictable according to an earlier value. As a result, efficient signal representations can be determined by estimating and applying certain prediction parameters to represent the signal.
Applying LPC techniques, a conventional source encoder operates on speech signals to extract modeling and parameter information for communication to a conventional source decoder via a communication channel. Once received, the decoder attempts to reconstruct a counterpart signal for playback that sounds to a human ear like the original speech.
A certain amount of communication channel bandwidth is required to communicate the modeling and parameter information to the decoder. In embodiments, for example where the channel bandwidth is shared and real-time reconstruction is necessary, a reduction in the required bandwidth proves beneficial. However, using conventional modeling techniques, the quality requirements in the reproduced speech limit the reduction of such bandwidth below certain levels.
Further limitations and disadvantages of conventional systems will become apparent to one of skill in the art after reviewing the remainder of the present application with reference to the drawings.
SUMMARY OF THE INVENTION
Various aspects of the present invention can be found in an embodiment of a speech encoder using an analysis by synthesis approach on a speech signal. The speech encoder comprises an adaptive codebook, a plurality of subcodebooks, and an encoder processing circuit. The encoder processing circuit utilizes parameters of the speech signal in favoring at least one of the plurality of subcodebooks over at least one other of the plurality of subcodebooks. Of course many variations are possible. For example, the speech signal may comprise a residual signal, and at least one of the parameters utilized may comprise pitch correlation, average to peak ratio, signal to noise ratio, etc. Similarly, the encoder processing circuit may also utilize a classifier in favoring the at least one of the plurality of subcodebooks over the at least one other of the plurality of subcodebooks.
Further aspects may be found in a similar speech encoder that also uses an analysis by synthesis approach on a speech signal. The speech encoder comprises a noise-like codebook, a pulse codebook, and an encoder processing circuit. The encoder processing circuit identifies a weighting to favor one of the noise-like codebook and the pulse codebook over one other of the noise-like codebook and the pulse codebook.
The identification of the weighting by the encoder processing circuit may involve consideration of pitch correlation, an average to peak ratio, and/or a signal to noise ratio. It may also involve application of a classifier which may, for example, identify a noise-like unvoiced residual. The identification of the weighting by the encoder processing circuit may also comprise applying a first weighting approach if a noise-like residual is detected, and a second weighting approach if the noise-like residual is not detected. The first and second weighting approaches may also both utilize a plurality of parameters extracted from the speech signal.
Other aspects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.


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W. B. Kleijn and

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