Speech signal quantization using human auditory models in predictive coding systems

• US 5,710,863 A
• Filed: 09/19/1995
• Issued: 01/20/1998
• Est. Priority Date: 09/19/1995
• Status: Expired due to Term

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Chen, Juin-Hwey
• Primary Examiner(s): MacDonald, Allen R.
• Assistant Examiner(s): Dorvil, Richemond
• Application Number:
  US08/530,980
• Time in Patent Office: 854 Days
• Field of Search: 395/2.09, 395/2.39, 395/2.38, 395/2.29, 395/2.28, 395/2.14, 395/2.16, 395/2.77, 395/2.31
• US Class Current: 704/200.1
• CPC Class Codes: G10L 19/002 Dynamic bit allocation for perceptual audio coders G10L19/032
• CPC Class Codes: G10L 19/0212 using orthogonal transformation
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
• CPC Class Codes: G10L 2019/0003 Backward prediction of gain
• CPC Class Codes: G10L 2019/0011 Long term prediction filters, i.e. pitch estimation
• CPC Class Codes: G10L 2019/0013 Codebook search algorithms
• CPC Class Codes: G10L 25/24 the extracted parameters being the cepstrum
• CPC Class Codes: G10L 25/27 characterised by the analysis technique

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

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.

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

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

4. 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.

5. 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.

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.

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

8. 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.

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

10. 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.