83 lines
2.3 KiB
C
83 lines
2.3 KiB
C
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#include <stdlib.h>
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#include <math.h>
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#include "panning.h"
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#ifndef PI
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#define PI 3.14159265359
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#endif
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#ifndef SQRT2
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#define SQRT2 1.414213562
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#endif
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#define RANGE 512
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//-----------------------------------------------------------------
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// Set the panning values for the two stereo channels (L,R)
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// for a position -256..0..256 L..C..R
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//-----------------------------------------------------------------
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void calc_panning(float channels[2], int position)
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{
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if ( position > RANGE / 2 )
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position = RANGE / 2;
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else if ( position < -RANGE / 2 )
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position = -RANGE / 2;
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position += RANGE / 2; // make -256..0..256 -> 0..256..512
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// Equal power law: equation is
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// right = sin( position / range * pi / 2) * sqrt( 2 )
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// left is equivalent to right with position = range - position
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// position is in the range 0 .. RANGE
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// RANGE / 2 = centre, result = 1.0f
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channels[1] = (float)( sin( (double)position / RANGE * PI / 2 ) * SQRT2 );
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position = RANGE - position;
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channels[0] = (float)( sin( (double)position / RANGE * PI / 2 ) * SQRT2 );
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}
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//-----------------------------------------------------------------
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// Reset the panning values to the centre position
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//-----------------------------------------------------------------
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void centre_panning(float channels[2])
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{
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channels[0] = channels[1] = 1.0f;
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}
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/*//-----------------------------------------------------------------
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// Generate a stereo position in the range 0..RANGE
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// with Gaussian distribution, mean RANGE/2, S.D. RANGE/5
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//-----------------------------------------------------------------
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int random_stereo()
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{
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int n = (int)(RANGE/2 + gauss_rand() * (RANGE * 0.2) );
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if ( n > RANGE ) n = RANGE;
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if ( n < 0 ) n = 0;
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return n;
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}
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//-----------------------------------------------------------------
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// Generate a Gaussian random number with mean 0, variance 1
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// Copied from an ancient C newsgroup FAQ
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//-----------------------------------------------------------------
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double gauss_rand()
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{
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static double V1, V2, S;
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static int phase = 0;
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double X;
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if(phase == 0) {
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do {
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double U1 = (double)rand() / RAND_MAX;
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double U2 = (double)rand() / RAND_MAX;
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V1 = 2 * U1 - 1;
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V2 = 2 * U2 - 1;
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S = V1 * V1 + V2 * V2;
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} while(S >= 1 || S == 0);
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X = V1 * sqrt(-2 * log(S) / S);
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} else
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X = V2 * sqrt(-2 * log(S) / S);
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phase = 1 - phase;
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return X;
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}*/
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