Digital Audio Signal Processing Using Even-Order Harmonic Generation
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Solution Overview
Problem
Digital audio signals lack high-frequency components due to the Nyquist frequency limit, resulting in poor audio quality when converted from analog signals, and existing methods either add uncomfortable odd-order harmonics or require extensive signal processing.
Innovation Solution
A method and apparatus that detect local maxima and minima in digital audio signals, calculate differences, and apply coefficients to generate even-order harmonics, which are then added to the signal to enhance quality, while optionally generating odd-order harmonics as well.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing methods add harmonics to compensate for lost high-frequency components, then audio quality is improved, but odd-order harmonics cause discomfort to listeners
Solution Approach 1:
The patent applies different processing to different harmonic components: even-order harmonics are generated and added to improve audio quality, while odd-order harmonics are suppressed or not generated to avoid listener discomfort. This selective treatment of different harmonic types resolves the contradiction by applying local quality differentiation to harmonic components.
Solution Approach 2:
The patent converts the limitation of Nyquist frequency (which causes loss of high-frequency components) into a benefit by selectively generating even-order harmonics that can extend the perceived frequency range without introducing the harmful odd-order harmonics that cause discomfort. The harm of high-frequency loss is transformed into a controlled harmonic generation process.
2Manufacturing precision
If waveform shaping is applied to add harmonics, then high-frequency components are restored, but the processing complexity increases
Solution Approach 1:
The patent extracts only the necessary even-order harmonic components from the waveform shaping process, rather than implementing full waveform shaping that would generate all harmonics. This selective extraction approach restores high-frequency components while minimizing processing complexity by focusing only on beneficial even-order harmonics.
Solution Approach 2:
The patent applies partial waveform shaping action by selectively generating only even-order harmonics rather than performing complete waveform shaping that would produce both even and odd-order harmonics. This partial action achieves the necessary high-frequency restoration with reduced computational complexity.
Data Source
AI summary
There is a sequence of samples having values representative of a waveform. Samples corresponding to extrema including maximums and minimums in the waveform are detected. A decision is made as to whether values of successive samples between every two extremum-corresponding samples are in an upward slope or a downward slope. The number of these successive samples is detected. One is selected from coefficients in response to the detected sample number. A first group has one or more samples adjacently preceding a maximum-corresponding sample. A second group has one or more samples adjacently following the maximum-corresponding sample. A third group has one or more samples adjacently preceding a minimum-corresponding sample. A fourth group has one or more samples adjacently following the minimum-corresponding sample. Each of specified samples among the samples in the first to fourth groups is corrected in response to the slope decision result and the selected coefficient.