# US 5,710,863 A · Speech signal quantization using human auditory models in predictive coding systems

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- Number: US 5,710,863 A
- Document ID: US5710863A
- Status: Granted
- Kind: A
- Application number: 08/530,980
- Filed: 1995-09-19
- Granted: 1998-01-20
- Earliest claimed: 1995-09-19
- Inventors: Juin-Hwey Chen
- Web page: https://patentgrep.com/patent/US5710863A

## CPC

- G10L 19/0212: {using orthogonal transformation}
- G10L 19/002: Dynamic bit allocation (for perceptual audio coders G10L19/032)
- G10L 19/06: Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
- G10L 25/24: the extracted parameters being the cepstrum
- G10L 25/27: characterised by the analysis technique
- G10L 2019/0003: {Backward prediction of gain}
- G10L 2019/0011: {Long term prediction filters, i.e. pitch estimation}
- G10L 2019/0013: {Codebook search algorithms}
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING

## Abstract

A speech compression system called "Transform Predictive Coding", or TPC, provides for encoding 7 kHz wideband speech (160 kHz sampling) at a target bit-rate range of 16 to 32 kb/s (1 to 2 bits/sample). The system uses short-term and long-term prediction to remove the redundancy in speech. A prediction residual is transformed and coded in the frequency domain to take advantage of knowledge in human auditory perception. The TPC coder uses only open-loop quantization and therefore has a fairly low complexity. The speech quality of TPC is essentially transparent at 32 kb/s, very good at 24 kb/s, and acceptable at 16 kb/s.

## Claims

### Claim 1

A method of coding a signal representing speech information, the method comprising:
generating a first signal representing an estimate of the signal representing speech information;
comparing the signal representing speech information with the first signal to form a second signal representing a difference between said compared signals;
determining a quantizer resolution in accordance with a perceptual noise masking signal which is determined by a model of human audio perception;
quantizing the second signal in accordance with the determined quantizer resolution; and
generating a coded signal based on said quantized signal.

### Claim 2 (depends on 1)

The method of claim 1 wherein the signal representing speech information comprises a linear prediction residual signal.

### Claim 3 (depends on 1)

The method of claim 1 wherein the signal representing speech information comprises a pitch prediction residual signal.

### Claim 4 (depends on 1)

The method of claim 1 wherein the signal representing speech information comprises a linear prediction residual signal which has been transformed into a frequency domain.

### Claim 5 (depends on 1)

The method of claim 1 wherein the step of determining the quantizer resolution comprises determining a noise masking threshold based on a frequency response of a quantized synthesis filter.

### Claim 6

A system for coding a signal representing speech information, the system comprising:
a first signal generator adapted to generate a first signal representing an estimate of the signal representing speech information;
a signal comparator adapted to compare the signal representing speech information with the first signal to form a second signal representing a difference between said compared signals;
a quantization resolution determination module adapted to determine a quantizer resolution in accordance with a perceptual noise masking signal which is determined by a model of human audio perception;
a quantizer adapted to quantize the second signal in accordance with the determined quantizer resolution; and
a second signal generator adapted to generate a coded signal based on said quantized signal.

### Claim 7 (depends on 6)

The system of claim 6 wherein the signal representing speech information comprises a linear prediction residual signal.

### Claim 8 (depends on 7)

The system of claim 7 wherein the quantization resolution determination module comprises means for determining a noise masking threshold based on a frequency response of a quantized synthesis filter.

### Claim 9 (depends on 6)

The system of claim 6 wherein the signal representing speech information comprises a pitch prediction residual signal.

### Claim 10 (depends on 6)

The system of claim 6 wherein the signal representing speech information comprises a linear prediction residual signal which has been transformed into a frequency domain.