Linear-phase fir audio filter, production method and signal processor
AssigneeRobert Bosch GmbH
InventorAxel Rohde
Life of this patent
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Abstract
Systems and methods for producing a linear-phase digital FIR filter from two sub-filters for an audio signal. In one method, the sub-filters are provided as sub-sets having numbers of coefficients, a lower cutoff frequency of the particular sub-filter being greater than the sampling frequency of the audio signal divided by the number. The sub-sets are linearly convoluted with one another so as to form a total set having a number of coefficients greater than the numbers, and the total set is symmetrically reduced to a number less than the number, so as to form a reduced total set of the filter. A linear-phase digital FIR filter for an audio signal is created by the method.
Claims9
A method for generating a linear-phase digital FIR filter (4) for an audio signal (AU, AF), wherein the filter (4) comprises two individual linear-phase digital FIR subfilters (6a,b) for respectively subfiltering the audio signal (AU, AF), in which:
- the two subfilters (6a,b) are provided as subsets (Ta,b) having a respective number (Ma,b) of coefficients,
- wherein a lower limit frequency (Ga,b) of the respective subfilter (6a,b) is greater than the ratio of the sampling frequency of the audio signal (AU, AF) divided by the respective number (Ma,b), the two subsets (Ta,b) are linearly convoluted with one another to form a sum set (SU) of which the number (L) of coefficients is the greater of the respective numbers (Ma,b) of the subsets (Ta,b), and the sum set (SU) is symmetrically truncated to a number (Z) which is less than the number (L), resulting in a truncated sum set (SK), in order to generate the filter (4) according to the truncated sum set (SK), and wherein a shelving filter is used as one of the two subfilters (6a,b).
Dependencies are inferred from the claim text.