Audio Encoding Using Frequency-Domain LPC and Temporal Envelope

Solution Overview

Problem

Existing frequency-domain-based audio coding technologies fail to effectively cover time-domain information, leading to distortion in decoded audio signals during the encoding process using linear predictive coding (LPC).

Innovation Solution

A method that combines current and previous audio signal blocks, applies frequency-domain LPC to extract linear prediction coefficients, generates a temporal envelope, and quantizes residual signals using either time-domain or frequency-domain quantization, optimizing noise reduction based on signal-to-noise ratio (SNR) to minimize time-domain distortion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If frequency-domain LPC is used for audio signal encoding, then encoding efficiency is improved, but time-domain information is lost causing distortion

Engineering Contradiction:

Improveencoding efficiencyVSAvoidtime-domain accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent transforms the residual signal from time-domain to frequency-domain using DFT, performs quantization in frequency-domain, then transforms back to time-domain using IDFT. This dimensional transformation allows frequency-domain processing benefits while recovering time-domain accuracy for distortion reduction.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent changes the quantization parameter domain from time-domain to frequency-domain by applying DFT transformation before quantization. This parameter change enables more efficient quantization in frequency-domain while maintaining time-domain signal integrity through proper transformation and inverse transformation.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If time-domain quantization is used for residual signal, then time-domain information is preserved, but quantization noise increases

Engineering Contradiction:

Improvetime-domain information preservationVSAvoidquantization noise

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent changes the quantization parameter domain from time-domain to frequency-domain by applying DFT transformation before quantization. This parameter change enables more efficient quantization in frequency-domain while maintaining time-domain signal integrity through proper transformation and inverse transformation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent substitutes time-domain quantization with frequency-domain quantization by introducing DFT and IDFT transformations. This substitution replaces the direct time-domain quantization mechanism with a frequency-domain processing mechanism that reduces quantization noise while preserving essential signal characteristics.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-generated harmful factors

If frequency-domain quantization is used for residual signal, then quantization noise is reduced, but time-domain information may be lost

Engineering Contradiction:

Improvequantization noise reductionVSAvoidtime-domain information preservation

Core Design Contradiction:

Object-generated harmful factorsVSManufacturing precision

Solution Approach 1:

The patent transforms the residual signal from time-domain to frequency-domain using DFT, performs quantization in frequency-domain, then transforms back to time-domain using IDFT. This dimensional transformation allows frequency-domain processing benefits while recovering time-domain accuracy for distortion reduction.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent substitutes time-domain quantization with frequency-domain quantization by introducing DFT and IDFT transformations. This substitution replaces the direct time-domain quantization mechanism with a frequency-domain processing mechanism that reduces quantization noise while preserving essential signal characteristics.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11562757B2Method of encoding and decoding audio signal using linear predictive coding and encoder and decoder performing the method

Publication Date: 2023.01.24 ELECTRONICS & TELECOMM RES INST

AI summary

An audio signal encoding method performed by an encoder includes identifying a time-domain audio signal in a unit of blocks, quantizing a linear prediction coefficient extracted from a combined block in which a current original block of the audio signal and a previous original block chronologically adjacent to the current original block using frequency-domain linear predictive coding (LPC), generating a temporal envelope by dequantizing the quantized linear prediction coefficient, extracting a residual signal from the combined block based on the temporal envelope, quantizing the residual signal by one of time-domain quantization and frequency-domain quantization, and transforming the quantized residual signal and the quantized linear prediction coefficient into a bitstream.