Audio High-Frequency Interpolation Using Adaptive Filter Coefficients
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Solution Overview
Problem
Existing high-frequency interpolation devices increase processing load and cost by doubling the sampling frequency, and fail to maintain continuous frequency characteristics in high-frequency interpolation, leading to reduced interpolation effects.
Innovation Solution
A high-frequency interpolation device that determines the frequency band of an audio signal and selects a filter coefficient for a high-pass filter to generate a high-frequency interpolation signal, adjusting the interpolation signal in accordance with the bandwidth, and performs frequency conversion to ensure continuous frequency characteristics without increasing the sampling rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If up-sampling is performed for a predetermined upper limit frequency to generate high-frequency interpolation signal, then high-frequency interpolation effect is improved, but processing load increases and device cost increases
Solution Approach 1:
The patent changes the parameter of sampling frequency from the conventional approach of doubling to the original frequency to maintaining the original sampling frequency. This is achieved by performing down-sampling followed by up-sampling with the same sampling frequency, thereby reducing processing load while maintaining interpolation effectiveness through spectral mirroring around the Nyquist frequency.
Solution Approach 2:
The patent inverts the conventional up-sampling approach by first performing down-sampling to create aliasing components, then applying high-pass filtering to extract the inverted spectrum, and finally up-sampling back to the original frequency. This inverted approach achieves high-frequency interpolation without increasing processing load.
2Manufacturing precision
If up-sampling frequency is doubled to achieve high-frequency interpolation, then interpolation signal quality is improved, but device cost increases
Solution Approach 1:
The patent changes the sampling frequency parameter from doubled frequency back to the original frequency, reducing the computational resources and hardware requirements needed for processing. This maintains interpolation signal quality through spectral manipulation while lowering device manufacturing cost.
3Device complexity
If fixed filter coefficient is used for high-pass filter, then device complexity is reduced, but frequency characteristics become discontinuous and interpolation effect is reduced
Solution Approach 1:
The patent makes the filter coefficient dynamic by determining it based on the bandwidth type of the input audio signal. The system analyzes the signal's frequency characteristics and selects appropriate filter coefficients accordingly, ensuring continuous frequency characteristics and effective interpolation while adapting to different signal types without requiring complex pre-defined coefficient sets.
Solution Approach 2:
The patent implements a feedback mechanism where the bandwidth type of the audio signal is determined and used to select the filter coefficient. This closed-loop approach ensures that the filter coefficient adapts to the signal characteristics, maintaining continuous frequency characteristics and improving interpolation effect while keeping device complexity manageable.
Data Source
AI summary
It is possible to generate an interpolation signal in which spectrum in frequency characteristics develops in a continuous manner according to a reproduced music without increasing the sampling rate (sampling frequency) in up-sampling processing. A high-frequency interpolation device 1 includes: a frequency band determination section 2 that determines a bandwidth type of an audio signal as a frequency band determination value preset for each bandwidth according to the frequency characteristics of the audio signal; and an interpolation signal generation section 3 that selects a filter coefficient of a high-pass filter in accordance with the frequency band determination value 2, performs filtering for the audio signal by using the high-pass filter having the selected filter coefficient, and generates a high-frequency interpolation signal for the audio signal.