Adaptive Spectral Patching for Audio 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 inefficiencies due to the use of a single patching algorithm that does not account for signal characteristics or implementation needs, particularly when switching between different domains.
Innovation Solution
Implementing a system that allows switching 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 synthesis audio signal, thereby avoiding the need for time-to-spectral domain transformations and enhancing perceptual quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single spectral domain patching algorithm is used for bandwidth extension, then the device complexity is reduced, but the adaptability to different signal characteristics deteriorates
Solution Approach 1:
The system dynamically switches between different spectral domain patching algorithms based on the characteristics of the input signal. The patching algorithm selection unit analyzes the signal and selects the most appropriate algorithm (e.g., harmonic transposition for tonal signals, non-harmonic copying for noise-like signals), making the system adaptive without requiring manual configuration or complex fixed-structure designs.
2Adaptability or versatility
If multiple patching algorithms are implemented with switching capability, then the adaptability to signal characteristics is improved, but the device complexity increases
Solution Approach 1:
The system segments the signal processing task by dividing it into distinct processing paths, each handling specific signal types. Different patching algorithms are organized in separate processing branches (e.g., harmonic transposition path, non-harmonic copying path), and the selection unit routes the signal to the appropriate path based on signal characteristics, managing complexity through structured organization.
Solution Approach 2:
The spectral domain patching apparatus is designed with multi-functionality, where a single system can perform multiple patching operations (harmonic transposition, non-harmonic copying, spectral band replication) depending on the input signal. This universal design allows one apparatus to handle diverse signal types without requiring separate dedicated systems for each algorithm.
3Adaptability or versatility
If time-to-spectral domain transformations are performed for patching, then the flexibility of patching algorithms is improved, but the computational complexity increases
Solution Approach 1:
The system replaces the mechanical transformation process (time-to-spectral domain conversion) with direct spectral domain processing. By operating natively in the spectral domain using FFT-based methods and spectral manipulation techniques, the system achieves the flexibility of multiple patching algorithms without the computational overhead of repeated time-frequency transformations.
4Device complexity
If a single patching algorithm is used without adaptation, then the device complexity is reduced, but blocking artifacts occur
Solution Approach 1:
The system changes the parameter of algorithm selection based on signal characteristics. By analyzing parameters such as signal type (tonal vs. noise-like), bandwidth requirements, and spectral content, the system dynamically adjusts which patching algorithm is applied, preventing blocking artifacts that would occur with a fixed single-algorithm approach while keeping the switching logic simple and parameter-driven.
Data Source
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.