Spectral Domain Audio Patching for Adaptive Bandwidth Extension

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Solution Overview

Problem

Existing bandwidth extension methods in audio coding, such as spectral band replication (SBR), lack flexibility and adaptability, leading to blocking artifacts and inefficient processing due to the use of a single patching algorithm that does not account for signal characteristics or domain-specific needs.

Innovation Solution

Implementing a system that switches between multiple spectral domain patching algorithms, including harmonic transposition, non-harmonic copying-up SBR, and non-linear distortion, within the spectral domain to generate a modified spectral representation, allowing for improved perceptual quality and reduced complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a single patching algorithm is used in existing bandwidth extension methods, then the processing is simpler, but the adaptability to different signal characteristics is poor and blocking artifacts occur

Engineering Contradiction:

Improveadaptability to signal characteristicsVSAvoidprocessing complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements dynamic switching between multiple patching algorithms (harmonic transposition, non-harmonic copying-up SBR, and non-linear distortion) based on signal characteristics and domain-specific needs. The system adapts the patching algorithm in real-time rather than using a fixed single algorithm, resolving the contradiction between adaptability and complexity by introducing controlled dynamic selection.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of algorithm selection by introducing multiple patching algorithms with different characteristics and switching between them based on signal analysis. This allows the system to adapt to different signal conditions (speech, music, transient signals) while maintaining manageable complexity through parameter-driven algorithm selection.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If multiple patching algorithms are implemented to improve adaptability, then the perceptual quality improves, but the processing complexity increases

Engineering Contradiction:

Improveperceptual qualityVSAvoidprocessing complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent segments the audio processing task by dividing it into different frequency bands (low-frequency core band and high-frequency upper band) and applying different patching algorithms to different segments based on their characteristics. This segmentation allows high perceptual quality through targeted algorithm application while controlling complexity by processing different bands independently with specialized algorithms.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different patching algorithms to different frequency bands and signal types (harmonic vs. non-harmonic content) to achieve local optimization. By matching specific algorithms to specific signal characteristics in different regions of the spectrum, the system achieves high perceptual quality where needed while avoiding unnecessary complexity in other regions.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If domain transformations are used in patching algorithms, then flexibility is achieved, but processing complexity and blocking artifacts increase

Engineering Contradiction:

Improveflexibility in patchingVSAvoidprocessing complexity and blocking artifacts

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent extracts and eliminates the domain transformation step from the patching process. By performing patching operations directly in the spectral domain without requiring transformations to time domain or other domains, the system maintains flexibility in algorithm selection while removing the source of blocking artifacts and reducing processing complexity associated with multiple domain conversions.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUSRE50693E1Apparatus and method for generating a synthesis audio signal and for encoding an audio signal

Publication Date: 2025.12.09 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

AI summary

An apparatus for generating a synthesis audio signal using a patching control signal has a first converter, a spectral domain patch generator, a high frequency reconstruction manipulator and a combiner. The first converter is configured for converting a time portion of an audio signal into a spectral representation. The spectral domain patch generator is configured for performing a plurality of different spectral domain patching algorithms, wherein each patching algorithm generates a modified spectral representation having spectral components in an upper frequency band derived from corresponding spectral components in a core frequency band of the audio signal. The spectral domain patch generator is furthermore configured to select a first spectral domain patching algorithm from the plurality of patching algorithms for a first time portion and a second spectral domain patching algorithm from the plurality of patching algorithm for a second different time portion in accordance with the patching control signal to obtain the modified spectral representation.