59 lines
1.7 KiB
C++
59 lines
1.7 KiB
C++
#ifndef FILTER_NFC_H
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#define FILTER_NFC_H
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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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struct NfcFilter4 {
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float base_gain, gain;
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float b1, b2, b3, b4, a1, a2, a3, a4;
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float z[4];
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};
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class NfcFilter {
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NfcFilter1 first;
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NfcFilter2 second;
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NfcFilter3 third;
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NfcFilter4 fourth;
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public:
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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
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* average speaker distance, or based on the reference delay if outputing
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* NFC-HOA. It must not be negative, 0, or infinite. The source distance
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* should not be too small relative to the control distance.
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*/
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void init(const float w0, const float w1) noexcept;
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void adjust(const float w0) noexcept;
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/* Near-field control filter for first-order ambisonic channels (1-3). */
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void process1(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 process2(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 process3(float *RESTRICT dst, const float *RESTRICT src, const int count);
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/* Near-field control filter for fourth-order ambisonic channels (16-24). */
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void process4(float *RESTRICT dst, const float *RESTRICT src, const int count);
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};
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#endif /* FILTER_NFC_H */
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