Audio Signal Processing Device for High Frequency Interpolation
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Solution Overview
Problem
High frequency interpolation of nonreversibly compressed audio signals often results in discontinuous frequency spectra and degraded sound quality due to fixed frequency band synthesis and inadequate consideration of audio signal level characteristics.
Innovation Solution
A signal processing device and method that corrects a reference signal based on audio signal frequency characteristics, generates an interpolation signal, and synthesizes it with the audio signal, using regression analysis and weighting values to ensure continuous spectral attenuation and prevent excessive high-frequency emphasis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high frequency interpolation is performed by synthesizing an interpolation signal of a fixed frequency band with an audio signal, then high frequency components are added to the audio signal, but the frequency spectrum becomes discontinuous and auditory sound quality degrades
Solution Approach 1:
The patent applies dynamics by making the reference signal's frequency band variable rather than fixed. The reference signal is dynamically adjusted based on the audio signal's frequency characteristics, allowing the interpolation to adapt to different frequency bands and maintain spectral continuity while adding high frequency components
Solution Approach 2:
The patent changes the parameter of frequency band from a fixed value to a variable value that depends on the audio signal's characteristics. By adjusting the reference signal's frequency band according to the audio signal's spectral properties, the system maintains continuous frequency spectra while interpolating high frequency components
2Productivity
If high frequency interpolation is performed without considering audio signal level characteristics, then interpolation is applied uniformly, but excessive high-frequency emphasis occurs and sound quality degrades
Solution Approach 1:
The patent applies local quality by adjusting the interpolation characteristics based on the audio signal's frequency characteristics. Different regions of the frequency spectrum are treated differently, with the reference signal's frequency band and attenuation characteristics being locally optimized for each audio signal to prevent excessive high-frequency emphasis while maintaining sound quality
Solution Approach 2:
The patent changes the interpolation parameters dynamically based on the audio signal's level characteristics. By adjusting the reference signal's frequency band and attenuation characteristics according to the audio signal's spectral properties, the system maintains appropriate high-frequency content without causing excessive emphasis or degradation of sound quality
Data Source
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AI summary
A signal processing device comprises: a band detecting means for detecting a frequency band which satisfies a predetermined condition from an audio signal; a reference signal generating means for generating a reference signal in accordance with a detection band by the band detecting means; a reference signal correcting means for correcting the generated reference signal on the basis of a frequency characteristic thereof; a frequency band extending means for extending the corrected reference signal up to a frequency band higher than the detection band; an interpolation signal generating means for generating an interpolation signal by weighting each frequency component within the extended frequency band in accordance with a frequency characteristic of the audio signal; and a signal synthesizing means for synthesizing the generated interpolation signal with the audio signal.