Adaptive Audio Oversampling for Transient High-Frequency Reconstruction
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Solution Overview
Problem
Existing high frequency reconstruction methods using phase vocoders face challenges in maintaining quality for transient sounds due to artifacts like waveform dispersion and temporal aliasing, which are not effectively addressed without increasing computational complexity.
Innovation Solution
An apparatus and method that separately treat transient and non-transient portions of audio signals, employing frequency domain oversampling only for transient parts, using a spectral converter and time converter to generate high frequency audio signals with adaptive oversampling controlled by a transient detector, thereby reducing complexity while preserving transient performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency domain oversampling is applied to all portions of the audio signal, then transient quality is improved, but computational complexity increases significantly
Solution Approach 1:
The patent applies frequency domain oversampling selectively only to transient portions of the audio signal rather than uniformly to the entire signal. The system detects transient regions and applies oversampling with factor K only during these regions, while using normal processing for non-transient portions, thereby achieving high transient quality without excessive computational burden throughout the entire signal processing chain
Solution Approach 2:
The oversampling factor is made dynamic and adaptive based on the detected transient characteristics. The system adjusts the oversampling factor K according to the transient strength and type detected in real-time, allowing the processing intensity to match the actual signal requirements, thus optimizing the balance between quality and computational complexity
2Measurement precision
If phase vocoder processing is used for high frequency reconstruction, then frequency resolution is improved, but transient artifacts such as waveform dispersion and temporal aliasing occur
Solution Approach 1:
The system performs preliminary detection of transient portions before applying phase vocoder processing. By identifying transient regions in advance, the system can apply special handling such as frequency domain oversampling and adjusted phase calculation methods specifically for these regions, preventing the occurrence of waveform dispersion and temporal aliasing artifacts before they manifest in the output signal
Solution Approach 2:
The patent modifies key processing parameters dynamically based on transient detection results. During transient portions, the system changes the oversampling factor, window function parameters, and phase calculation methods to values optimized for transient preservation, thereby reducing artifacts while maintaining the frequency resolution benefits of phase vocoder processing
3Reliability
If computational measures are applied to reduce transient artifacts, then transient quality is improved, but computational complexity increases
Solution Approach 1:
Instead of applying complex artifact reduction measures to the entire audio signal, the system applies these measures partially only to detected transient portions. This selective application ensures that computational resources are concentrated where they are most needed (during transients) while avoiding unnecessary computation during non-transient periods, thus improving transient quality without proportionally increasing overall computational complexity
Data Source
AI summary
An apparatus for generating a high frequency audio signal that includes an analyzer for analyzing an input signal to determine a transient information adaptively. Additionally a spectral converter is provided for converting the input signal into an input spectral representation. A spectral processor processes the input spectral representation to generate a processed spectral representation including values for higher frequencies than the input spectral representation. A time converter is configured for converting the processed spectral representation to a time representation, wherein the spectral converter or the time converter are controllable to perform a frequency domain oversampling for the first portion of the input signal having the transient information associated and to not perform the frequency domain oversampling for the second portion of the input signal not having the associated transient information.