Alc/nfcfilter.h

   1 #ifndef NFCFILTER_H
   2 #define NFCFILTER_H
   3
   4 #include "alMain.h"
   5
   6 typedef struct NfcFilter {
   7     float g;
   8     float coeffs[MAX_AMBI_ORDER*2 + 1];
   9     float history[MAX_AMBI_ORDER];
  10 } NfcFilter;
  11
  12 /* NOTE:
  13  * w0 = speed_of_sound / (source_distance * sample_rate);
  14  * w1 = speed_of_sound / (control_distance * sample_rate);
  15  *
  16  * Generally speaking, the control distance should be approximately the average
  17  * speaker distance, or based on the reference delay if outputing NFC-HOA. It
  18  * must not be negative, 0, or infinite. The source distance should not be too
  19  * small relative to the control distance.
  20  */
  21
  22 /* Near-field control filter for first-order ambisonic channels (1-3). */
  23 void NfcFilterCreate1(NfcFilter *nfc, const float w0, const float w1);
  24 void NfcFilterAdjust1(NfcFilter *nfc, const float w0);
  25 void NfcFilterUpdate1(NfcFilter *nfc, float *restrict dst, const float *restrict src, const int count);
  26
  27 /* Near-field control filter for second-order ambisonic channels (4-8). */
  28 void NfcFilterCreate2(NfcFilter *nfc, const float w0, const float w1);
  29 void NfcFilterAdjust2(NfcFilter *nfc, const float w0);
  30 void NfcFilterUpdate2(NfcFilter *nfc, float *restrict dst, const float *restrict src, const int count);
  31
  32 /* Near-field control filter for third-order ambisonic channels (9-15). */
  33 void NfcFilterCreate3(NfcFilter *nfc, const float w0, const float w1);
  34 void NfcFilterAdjust3(NfcFilter *nfc, const float w0);
  35 void NfcFilterUpdate3(NfcFilter *nfc, float *restrict dst, const float *restrict src, const int count);
  36
  37 #endif /* NFCFILTER_H */