Adaptive Attenuation for Low-Accuracy Audio Spectral Regions

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Solution Overview

Problem

Conventional audio coding systems face challenges in attenuating spectral regions with low accuracy, leading to loud signal distortions and changes in frequency characteristics, especially at low bitrates where certain spectral regions are coded with insufficient or no bits, resulting in poor reconstruction quality.

Innovation Solution

An adaptive attenuation scheme is introduced, where spectral regions to be attenuated are identified, grouped into continuous regions, and attenuation is applied based on the width of these regions, allowing for more aggressive attenuation without altering audible signal frequency characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If strong attenuation is applied to low-accuracy coded spectral regions, then unwanted distortion is masked, but loudness loss and change of frequency characteristics occur

Engineering Contradiction:

Improveunwanted distortionVSAvoidaudio quality

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent applies dynamic attenuation by adjusting the attenuation factor based on the width of the spectral region. Narrow spectral regions receive stronger attenuation to mask distortion, while wider regions receive weaker attenuation to preserve audio quality and frequency characteristics. This dynamic adjustment resolves the contradiction by adapting the attenuation strength to the specific characteristics of each spectral region.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements local quality by applying different attenuation levels to different spectral regions based on their individual widths. Each spectral region is treated differently - narrow regions get stronger attenuation while wider regions get weaker attenuation. This localized approach allows distortion masking in specific areas without compromising overall audio quality.

Inventive Principle:

Principle #3Local quality

2Reliability

If conventional conservative attenuation is applied, then audio quality is maintained, but audible noise in reconstructed regions persists

Engineering Contradiction:

Improveaudio qualityVSAvoidaudible noise

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent overcomes the limitation of conservative attenuation by introducing dynamic attenuation factors based on spectral region width. Instead of uniform conservative attenuation, the system applies stronger attenuation where needed (narrow regions) while maintaining quality where possible (wide regions), thereby reducing audible noise without sacrificing audio quality.

Inventive Principle:

Principle #15Dynamics

3Measurement precision

If more bits are assigned to spectral regions, then reconstruction quality improves, but bitrate consumption increases

Engineering Contradiction:

Improvereconstruction qualityVSAvoidbitrate

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent converts the harm of low-bitrate coding (poor reconstruction quality in certain spectral regions) into a benefit by using the spectral region width as a criterion for adaptive attenuation. Regions with insufficient bits are identified by their width characteristics and receive appropriate attenuation, transforming the bitrate limitation into an opportunity for intelligent quality management.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentUS9691398B2Method and a decoder for attenuation of signal regions reconstructed with low accuracy

Publication Date: 2017.06.27 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

The embodiments of the present invention improves conventional attenuation schemes by replacing constant attenuation with an adaptive attenuation scheme that allows more aggressive attenuation, without introducing audible change of signal frequency characteristics.