Minimum Phase FIR Filter Coefficient Generation for Audio Systems
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Solution Overview
Problem
Existing filter generation apparatuses are insufficient for multi-speaker systems and crossover processing, requiring increased memory capacity for storing parameters related to frequency band division and amplitude correction.
Innovation Solution
A filter generation apparatus that acquires and processes filter coefficients to generate approximation filters by converting linear phase FIR filters to minimum phase FIR filters, using cut-out and rounding processing with a window function, and storing coefficients only when the error is within a predetermined threshold, thereby reducing memory usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filter generation apparatus is used for multi-speaker systems and crossover processing, then audio quality and frequency band division are improved, but memory capacity requirements increase
Solution Approach 1:
The patent transforms the filter coefficient representation from linear phase to minimum phase domain, changing the mathematical parameters to achieve a more compact form that requires less memory storage while maintaining audio processing functionality
Solution Approach 2:
The patent extracts only the essential filter coefficients needed for approximation, storing them in a coefficient storage unit, and generates approximation filters on-demand through cut-out processing and window function application, rather than storing all possible filter parameters
2Adaptability or versatility
If filter coefficients are stored for each processing parameter in multi-speaker systems, then frequency band division and amplitude correction functions are improved, but device complexity increases
Solution Approach 1:
The minimum phase filter coefficient storage unit serves multiple purposes: it stores coefficients for both crossover processing and amplitude correction, and enables generation of approximation filters for different frequency bands through a unified process, reducing the need for separate storage for each function
Solution Approach 2:
The patent segments the filter coefficient data into minimum phase components that can be independently processed and recombined, allowing flexible generation of different frequency band filters through cut-out processing and window function application
Data Source
AI summary
A filter generation apparatus includes: a coefficient calculation unit that performs IFFT on a frequency characteristic of a frequency domain filter and calculates a filter coefficient of a linear phase FIR filter; a conversion unit that converts the filter coefficient to a filter coefficient of a minimum phase FIR filter; a coefficient generation unit that generates a filter coefficient of an approximation filter by executing cut-out processing to a filter length set by a filter length setting unit and rounding processing performed by a window function on the filter coefficient; an error calculation unit that calculates an error of a frequency characteristic corresponding to the approximation filter with respect to the frequency characteristic of the frequency domain filter; and a filter storage unit that stores the filter coefficient therein as a filter coefficient that specifies a new filter when the error is equal to or less than a predetermined threshold value.