Filter generator, filter generation method, and filter generation program

A filter generation method used by a filter generator that generates a filter for performing a sound correction process on an audio signal by fast-Fourier-transforming, then filtering, and inverse-fast-Fourier-transforming the audio signal, the filter generator comprising:

• a weighting factor storage unit configured to store weighting factor information used to perform the sound correction process, for each of a plurality of bands obtained by dividing a frequency band of the audio signal;
• and
• a gain coefficient storage unit configured to store preceding gain values of the divided bands set by a user before a preceding sound correction process and a preceding filter used in the preceding sound correction process, the method comprising:
• an input detection step of detecting, by an input detection unit, a band selected by the user, of the divided bands as band information and detecting a new gain value newly set by the user for the selected band;
• a weighting factor extraction step of extracting, by a weighting factor extraction unit, weighting factor information of the band selected by the user from the weighting factor storage unit on the basis of the band information detected in the input detection step;
• a gain difference calculation step of calculating, by a gain difference calculation unit, a difference between a preceding gain value of the band obtained from the band information, of the preceding gain values stored in the gain coefficient storage unit and the new gain value detected in the input detection step, as a gain difference;
• a correction gain generation step of generating, by a correction gain generation unit, a correction gain of the band obtained from the band information by multiplying the weighting factor information extracted in the weighting factor extraction step and the gain difference calculated in the gain difference calculation step;
• and
• a filter coefficient calculation step of generating, by a filter coefficient calculation unit, a new filter by multiplying a coefficient of the band obtained from the band information, of the preceding filter stored in the gain coefficient storage unit by the correction gain generated in the correction gain generation step.

A filter generation program for performing, using a computer of a filter generator, a function of generating a filter for performing a sound correction process on an audio signal by fast-Fourier-transforming, then filtering, and inverse-fast-Fourier-transforming the audio signal, the filter generator comprising:

• a weighting factor storage unit configured to store weighting factor information used to perform the sound correction process, for each of a plurality of bands obtained by dividing a frequency band of the audio signal;
• and
• a gain coefficient storage unit configured to store preceding gain values of the divided bands set by a user before a preceding sound correction process and a preceding filter used in the preceding sound correction process, the filter generation program causing the computer to perform:
• an input detection function of detecting a band selected by the user, of the divided bands as band information and detecting a new gain value newly set by the user for the selected band;
• a weighting factor extraction function of extracting weighting factor information of the band selected by the user from the weighting factor storage unit on the basis of the band information detected by the input detection function;
• a gain difference calculation function of calculating, as a gain difference, a difference between a preceding gain value of the band obtained from the band information, of the preceding gain values stored in the gain coefficient storage unit and the new gain value detected by the input detection function;
• a correction gain generation function of generating a correction gain of the band obtained from the band information by multiplying the weighting factor information extracted by the weighting factor extraction function and the gain difference calculated by the gain difference calculation function;
• and
• a filter coefficient calculation function of generating a new filter by multiplying a coefficient of the band obtained from the band information, of the preceding filter stored in the gain coefficient storage unit by the correction gain generated by the correction gain generation function.