Time Domain Spectral Bandwidth Replication for Low Latency Audio

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Solution Overview

Problem

Conventional Spectral Bandwidth Replication (SBR) techniques induce latency due to parameter estimation being performed in the frequency domain rather than the time domain, which hinders their integration into codecs without additional coding delay.

Innovation Solution

Implementing SBR fully in the time domain by separating audio signals into high and low bands, encoding the low band directly, classifying the high band signal, determining a template, generating an artificial high band signal, and transmitting a bit stream for decoding and reconstruction, thereby eliminating extra coding delay.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If SBR parameter estimation is performed in the frequency domain (transfer domain), then spectral bandwidth replication can be achieved, but latency is induced due to the transformation process

Engineering Contradiction:

Improvespectral bandwidth replication accuracyVSAvoidcoding delay

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces the frequency domain transformation mechanism (DCT or filter bank) with a time domain autocorrelation mechanism. Instead of transforming signals to frequency domain for parameter estimation, the invention performs autocorrelation analysis directly in the time domain to estimate high band parameters, thereby eliminating the transformation-induced latency while maintaining spectral replication capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the domain parameter from frequency domain to time domain for performing parameter estimation. By computing autocorrelation in the time domain and using it to derive high band parameters, the system achieves spectral bandwidth replication without the time penalty of frequency domain transformations

Inventive Principle:

Principle #35Parameter changes

2Loss of information

If conventional SBR techniques are used, then high band signal reconstruction is achieved, but additional coding delay is introduced that hinders codec integration

Engineering Contradiction:

Improvehigh band signal recoveryVSAvoidcodec processing speed

Core Design Contradiction:

Loss of informationVSProductivity

Solution Approach 1:

The patent performs preliminary autocorrelation analysis in the time domain to extract high band parameters before signal reconstruction. By pre-computing the autocorrelation function and using it to estimate high band spectral characteristics, the system prepares necessary parameters in advance without requiring subsequent frequency domain transformations, thus reducing overall coding delay

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention substitutes the frequency domain parameter estimation mechanism with a time domain autocorrelation-based mechanism. This replacement eliminates the transform-detransform cycle inherent in conventional SBR, enabling faster processing and better codec integration while maintaining high band signal reconstruction quality

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS11670311B2Time domain spectral bandwidth replication

Publication Date: 2023.06.06 SHURE ACQUISITION HLDG INC

AI summary

A wireless audio system for encoding and decoding an audio signal using spectral bandwidth replication is provided. Bandwidth extension is performed in the time-domain, enabling low-latency audio coding.