Two-Channel Sound Coding with Correlation-Based Mode Switching

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Solution Overview

Problem

Existing techniques for coding 2-channel sound signals result in redundant arithmetic processing and code amounts, particularly in scenarios where sound signals from a single source collected by two microphones are processed, leading to potential sound quality deterioration.

Innovation Solution

A method for coding 2-channel sound signals involves obtaining a downmix signal, determining left-right time differences, and using delayed or non-delayed downmix signals based on these differences to calculate subtraction gains and codes, followed by decoding these signals to minimize arithmetic processing and code amounts while maintaining sound quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If monaural coding is applied to 2-channel sound signals with small correlation between channels, then coding efficiency is improved, but arithmetic processing amount and code amount become redundant when channels have large correlation

Engineering Contradiction:

Improvecoding efficiencyVSAvoidarithmetic processing amount

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent dynamically switches between monaural coding and stereo coding modes based on the correlation between left and right channel signals. When correlation is small, monaural coding is used; when correlation is large, stereo coding is used. This dynamic adaptation resolves the contradiction by adjusting the coding strategy to match the actual signal characteristics, avoiding redundant processing while maintaining efficiency.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the coding parameter (coding mode) based on the correlation parameter between channels. By calculating the correlation and adjusting the coding approach accordingly, the system optimizes both arithmetic processing amount and coding efficiency for different signal scenarios.

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If monaural coding is applied to 2-channel sound signals, then code amount is reduced, but sound quality deterioration occurs when channels have large correlation

Engineering Contradiction:

Improvecode amountVSAvoidsound quality

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent dynamically selects between monaural and stereo coding modes based on channel correlation. When correlation is large, stereo coding is used to preserve sound quality; when correlation is small, monaural coding is used to reduce code amount. This dynamic selection resolves the contradiction between code amount and sound quality.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the coding mode parameter based on the correlation parameter, ensuring that sound quality is maintained when channels are highly correlated while reducing code amount when they are not.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If stereo coding is applied to 2-channel sound signals with large channel correlation, then sound quality is improved, but arithmetic processing amount increases

Engineering Contradiction:

Improvesound qualityVSAvoidarithmetic processing amount

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses dynamic mode switching based on correlation analysis. Stereo coding is applied only when channel correlation is large, avoiding unnecessary arithmetic processing when correlation is small. This resolves the contradiction by making arithmetic processing amount proportional to actual need.

Inventive Principle:

Principle #15Dynamics

4Ease of operation

If conventional coding is applied without considering channel correlation, then processing is simplified, but code amount becomes redundant and sound quality deteriorates

Engineering Contradiction:

Improveprocessing simplicityVSAvoidcode amount

Core Design Contradiction:

Ease of operationVSQuantity of substance

Solution Approach 1:

The patent performs preliminary correlation analysis between channels before selecting the coding mode. This preliminary action allows the system to choose the appropriate coding strategy in advance, avoiding redundant code generation while maintaining processing simplicity through automated decision-making.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses feedback from correlation analysis to adjust the coding mode. The correlation result feeds back into the coding decision process, enabling the system to adapt to signal characteristics and optimize code amount automatically.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS12374343B2Sound signal encoding method, sound signal decoding method, sound signal encoding apparatus, sound signal decoding apparatus, program, and recording medium

Publication Date: 2025.07.29 NT T INC

AI summary

A downmix unit 110 obtains downmix signals which are signals obtained by mixing input sound signals of a left channel input and input sound signals of a right channel input. In a case where the left channel is preceding, the downmix signals are determined to be used as is in a left channel subtraction gain estimation unit 120 and a left channel signal subtraction unit 130, and delayed downmix signals are determined to be used in a right channel subtraction gain estimation unit 140 and a right channel signal subtraction unit 150. In a case where the right channel is preceding, the downmix signals are determined to be used as is in the right channel subtraction gain estimation unit 140 and the right channel signal subtraction unit 150, and delayed downmix signals are determined to be used in the left channel subtraction gain estimation unit 120 and the left channel signal subtraction unit 130.