58 lines
1.6 KiB
C
58 lines
1.6 KiB
C
#ifndef FILTER_NFC_H
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#define FILTER_NFC_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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struct NfcFilter1 {
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float base_gain, gain;
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float b1, a1;
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float z[1];
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};
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struct NfcFilter2 {
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float base_gain, gain;
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float b1, b2, a1, a2;
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float z[2];
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};
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struct NfcFilter3 {
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float base_gain, gain;
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float b1, b2, b3, a1, a2, a3;
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float z[3];
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};
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typedef struct NfcFilter {
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struct NfcFilter1 first;
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struct NfcFilter2 second;
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struct NfcFilter3 third;
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} NfcFilter;
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/* NOTE:
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* w0 = speed_of_sound / (source_distance * sample_rate);
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* w1 = speed_of_sound / (control_distance * sample_rate);
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*
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* Generally speaking, the control distance should be approximately the average
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* speaker distance, or based on the reference delay if outputing NFC-HOA. It
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* must not be negative, 0, or infinite. The source distance should not be too
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* small relative to the control distance.
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*/
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void NfcFilterCreate(NfcFilter *nfc, const float w0, const float w1);
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void NfcFilterAdjust(NfcFilter *nfc, const float w0);
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/* Near-field control filter for first-order ambisonic channels (1-3). */
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void NfcFilterProcess1(NfcFilter *nfc, float *RESTRICT dst, const float *RESTRICT src, const int count);
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/* Near-field control filter for second-order ambisonic channels (4-8). */
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void NfcFilterProcess2(NfcFilter *nfc, float *RESTRICT dst, const float *RESTRICT src, const int count);
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/* Near-field control filter for third-order ambisonic channels (9-15). */
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void NfcFilterProcess3(NfcFilter *nfc, float *RESTRICT dst, const float *RESTRICT src, const int count);
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#ifdef __cplusplus
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} // extern "C"
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#endif
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#endif /* FILTER_NFC_H */
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