USAC Window Sequences with Extended Overlap-Add for LPD-FD Switching

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Solution Overview

Problem

Conventional Unified Speech and Audio Codec (USAC) methods do not effectively improve coding efficiency through optimal window sequence processing during mode switching between Linear Prediction Domain (LPD) and Frequency Domain (FD) modes, leading to potential block artifacts and reduced coding gain.

Innovation Solution

The USAC employs extended overlap-add regions between frames during mode switching, adjusting window sequences based on previous and next sub-frames' LPD modes, and utilizing MDCT-based Time Domain Aliasing Cancellation (TDAC) to minimize time domain aliasing and enhance coding efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If mode switching is performed between LPD and FD modes in conventional USAC, then coding flexibility is improved, but block artifacts occur and coding gain is reduced

Engineering Contradiction:

Improvecoding flexibilityVSAvoidcoding gain

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by extending the overlap-add region between frames during mode switching. This preparatory extension of the transition region allows for smoother mode transitions between LPD and FD modes, preventing block artifacts before they occur and maintaining coding gain while preserving coding flexibility.

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If conventional window sequence processing is used during mode switching, then processing complexity is reduced, but block artifacts are generated and coding efficiency is degraded

Engineering Contradiction:

Improveprocessing complexityVSAvoidcoding efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent applies parameter changes by dynamically adjusting the window sequence parameters during mode switching. Specifically, the overlap-add region extension modifies the temporal parameters of the window function, enabling smoother transitions that improve coding efficiency while keeping the processing complexity manageable through systematic parameter adjustment.

Inventive Principle:

Principle #35Parameter changes

3Speed

If mode switching occurs between LPD modes with standard window sequences, then encoding speed is maintained, but time domain aliasing increases and sound quality deteriorates

Engineering Contradiction:

Improveencoding speedVSAvoidsound quality

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent applies the intermediary principle by introducing an extended overlap-add region as a mediator during mode switching between LPD modes. This extended transition region acts as an intermediary buffer that reduces time domain aliasing effects, thereby improving sound quality while maintaining encoding speed through efficient processing of the extended region.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12361957B2Unified speech/audio codec (USAC) processing windows sequence based mode switching

Publication Date: 2025.07.15 ELECTRONICS & TELECOMM RES INST

AI summary

A Unified Speech and Audio Codec (USAC) that may process a window sequence based on mode switching is provided. The USAC may perform encoding or decoding by overlapping between frames based on a folding point when mode switching occurs. The USAC may process different window sequences for each situation to perform encoding or decoding, and thereby may improve a coding efficiency.