Audio Decoder Roughness Removal via Spectral Side-Peak Attenuation

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Solution Overview

Problem

Existing audio coding technologies at low bitrates struggle to effectively remove auditory roughness artifacts, particularly those caused by quantization errors, which are difficult to mitigate without increasing bit allocation to tonal components, and current methods fail to distinguish between original and encoding-induced noise in polyphonic signals.

Innovation Solution

An apparatus and method that utilize a psycho-acoustical model to selectively remove spectral side-peaks associated with roughness artifacts, guided by auxiliary information transmitted from the encoder, which identifies intervals where encoding-induced roughness occurs, using a combination of signal analysis and processing to attenuate these peaks while preserving the original signal quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If quantization is applied to tonal components at very low bitrates, then audio compression efficiency is improved, but auditory roughness artifacts are introduced

Engineering Contradiction:

Improvecompression efficiencyVSAvoidauditory roughness

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent detects modulation artifacts (roughness) caused by quantization and converts this harmful effect into a beneficial one by using the detected information to guide selective spectral shaping. The roughness detection mechanism itself becomes the basis for targeted correction, transforming the problem into a solution pathway.

Inventive Principle:

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

Solution Approach 2:

Instead of applying uniform quantization across all frequency bands, the patent applies local quality control by identifying specific spectral regions where roughness occurs and applying targeted processing only to those regions. This allows high-quality preservation in clean regions while applying compression in regions where roughness is detected.

Inventive Principle:

Principle #3Local quality

2Measurement precision

If spectral band replication is used to extend audio bandwidth at low bitrates, then audio quality is improved, but roughness artifacts are amplified

Engineering Contradiction:

Improveaudio qualityVSAvoidroughness artifacts

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent performs preliminary roughness detection on the decoded signal before further processing. By detecting modulation artifacts early in the decoding chain, the system can preemptively apply corrective spectral shaping to prevent roughness amplification during subsequent processing stages.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements a feedback mechanism where the output of the roughness detector feeds into the spectral shaping processor. This closed-loop approach allows the system to continuously monitor and adjust the spectral content to minimize roughness while maintaining audio quality.

Inventive Principle:

Principle #23Feedback

3Object-affected harmful factors

If post-filtering is applied to suppress noise in tonal signals, then roughness is reduced, but the method fails for polyphonic signals with multiple pitches

Engineering Contradiction:

ImproveroughnessVSAvoidapplicability to polyphonic signals

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent develops a universal roughness detection and processing approach that works across different signal types including mono, stereo, and polyphonic content. The spectral shaping mechanism is designed to be pitch-agnostic, detecting and addressing roughness based on modulation patterns rather than specific frequency relationships, making it applicable to any audio content.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent changes the fundamental parameter used for roughness detection from pitch-based methods to modulation-rate-based methods. By detecting roughness through temporal modulation analysis rather than pitch correlation, the system becomes adaptable to polyphonic signals where multiple pitches coexist without interfering with the detection mechanism.

Inventive Principle:

Principle #35Parameter changes

4Productivity

If transform coding is used with short-term windowing, then computational efficiency is improved, but tonal components are misrepresented causing roughness

Engineering Contradiction:

Improvecomputational efficiencyVSAvoidtonal component representation

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent replaces the mechanical short-term windowing approach with a post-processing spectral shaping mechanism. Instead of relying on the transform coder's windowing to preserve tonal accuracy, the system uses modulation artifact detection and spectral shaping to correct representation errors after transformation, achieving both efficiency and accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS20240194209A1Apparatus and method for removing undesired auditory roughness

Publication Date: 2024.06.13 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

AI summary

An apparatus for processing an audio input signal to obtain an audio output signal according to an embodiment. The apparatus has a signal analyser configured for determining information on an auditory roughness of one or more spectral bands of the audio input signal. Moreover, the apparatus has a signal processor configured for processing the audio input signal depending on the information on the auditory roughness of the one or more spectral bands.