ref: 653e85a92f58a1aab94793e209e12fde6a8d734b
dir: /src/pt2_downsample2x.c/
// for finding memory leaks in debug mode with Visual Studio #if defined _DEBUG && defined _MSC_VER #include <crtdbg.h> #endif /* High-quality /2 decimator from ** https://www.musicdsp.org/en/latest/Filters/231-hiqh-quality-2-decimators.html */ #include <stdint.h> #include <stdbool.h> #include <stdlib.h> #include "pt2_helpers.h" // ABS() // ---------------------------------------------------------- // reserved for main audio channel mixer, PAT2SMP and MOD2WAV // ---------------------------------------------------------- static double R1_L, R2_L, R3_L, R4_L, R5_L, R6_L, R7_L, R8_L, R9_L; static double R1_R, R2_R, R3_R, R4_R, R5_R, R6_R, R7_R, R8_R, R9_R; void clearMixerDownsamplerStates(void) { R1_L = R2_L = R3_L = R4_L = R5_L = R6_L = R7_L = R8_L = R9_L = 0.0; R1_R = R2_R = R3_R = R4_R = R5_R = R6_R = R7_R = R8_R = R9_R = 0.0; } double decimate2x_L(double x0, double x1) { const double h0 = 8192.0 / 16384.0; const double h1 = 5042.0 / 16384.0; const double h3 = -1277.0 / 16384.0; const double h5 = 429.0 / 16384.0; const double h7 = -116.0 / 16384.0; const double h9 = 18.0 / 16384.0; double h9x0 = h9*x0; double h7x0 = h7*x0; double h5x0 = h5*x0; double h3x0 = h3*x0; double h1x0 = h1*x0; double R10 = R9_L+h9x0; R9_L = R8_L+h7x0; R8_L = R7_L+h5x0; R7_L = R6_L+h3x0; R6_L = R5_L+h1x0; R5_L = R4_L+h1x0+h0*x1; R4_L = R3_L+h3x0; R3_L = R2_L+h5x0; R2_L = R1_L+h7x0; R1_L = h9x0; return R10; } double decimate2x_R(double x0, double x1) { const double h0 = 8192.0 / 16384.0; const double h1 = 5042.0 / 16384.0; const double h3 = -1277.0 / 16384.0; const double h5 = 429.0 / 16384.0; const double h7 = -116.0 / 16384.0; const double h9 = 18.0 / 16384.0; double h9x0 = h9*x0; double h7x0 = h7*x0; double h5x0 = h5*x0; double h3x0 = h3*x0; double h1x0 = h1*x0; double R10 = R9_R+h9x0; R9_R = R8_R+h7x0; R8_R = R7_R+h5x0; R7_R = R6_R+h3x0; R6_R = R5_R+h1x0; R5_R = R4_R+h1x0+h0*x1; R4_R = R3_R+h3x0; R3_R = R2_R+h5x0; R2_R = R1_R+h7x0; R1_R = h9x0; return R10; } // ---------------------------------------------------------- // ---------------------------------------------------------- // ---------------------------------------------------------- static double R1, R2, R3, R4, R5, R6, R7, R8, R9; static void clearDownsamplerState(void) { R1 = R2 = R3 = R4 = R5 = R6 = R7 = R8 = R9 = 0.0; } static double decimate2x(double x0, double x1) { const double h0 = 8192.0 / 16384.0; const double h1 = 5042.0 / 16384.0; const double h3 = -1277.0 / 16384.0; const double h5 = 429.0 / 16384.0; const double h7 = -116.0 / 16384.0; const double h9 = 18.0 / 16384.0; double h9x0 = h9*x0; double h7x0 = h7*x0; double h5x0 = h5*x0; double h3x0 = h3*x0; double h1x0 = h1*x0; double R10 = R9+h9x0; R9 = R8+h7x0; R8 = R7+h5x0; R7 = R6+h3x0; R6 = R5+h1x0; R5 = R4+h1x0+h0*x1; R4 = R3+h3x0; R3 = R2+h5x0; R2 = R1+h7x0; R1 = h9x0; return R10; } // Warning: These can exceed original range because of undershoot/overshoot! void downsample2xDouble(double *buffer, uint32_t originalLength) { clearDownsamplerState(); const double *input = buffer; const uint32_t length = originalLength / 2; for (uint32_t i = 0; i < length; i++, input += 2) buffer[i] = decimate2x(input[0], input[1]); } void downsample2xFloat(float *buffer, uint32_t originalLength) { clearDownsamplerState(); const float *input = buffer; const uint32_t length = originalLength / 2; for (uint32_t i = 0; i < length; i++, input += 2) buffer[i] = (float)decimate2x(input[0], input[1]); } // Warning: These are slow and use normalization to prevent clipping from undershoot/overshoot! bool downsample2x8BitU(uint8_t *buffer, uint32_t originalLength) { double *dBuffer = (double *)malloc(originalLength * sizeof (double)); if (dBuffer == NULL) return false; for (uint32_t i = 0; i < originalLength; i++) dBuffer[i] = (buffer[i] - 128) * (1.0 / (INT8_MAX+1.0)); const double *input = dBuffer; double dPeak = 0.0; clearDownsamplerState(); const uint32_t length = originalLength / 2; for (uint32_t i = 0; i < length; i++, input += 2) { double dOut = decimate2x(input[0], input[1]); dBuffer[i] = dOut; dOut = ABS(dOut); if (dOut > dPeak) dPeak = dOut; } // normalize double dAmp = 1.0; if (dPeak > 0.0) dAmp = INT8_MAX / dPeak; for (uint32_t i = 0; i < length; i++) { double dSmp = dBuffer[i] * dAmp; // faster than calling round() if (dSmp < 0.0) dSmp -= 0.5; else if (dSmp > 0.0) dSmp += 0.5; buffer[i] = (uint8_t)dSmp + 128; } free(dBuffer); return true; } bool downsample2x8Bit(int8_t *buffer, uint32_t originalLength) { double *dBuffer = (double *)malloc(originalLength * sizeof (double)); if (dBuffer == NULL) return false; for (uint32_t i = 0; i < originalLength; i++) dBuffer[i] = buffer[i] * (1.0 / (INT8_MAX+1.0)); const double *input = dBuffer; double dPeak = 0.0; clearDownsamplerState(); const uint32_t length = originalLength / 2; for (uint32_t i = 0; i < length; i++, input += 2) { double dOut = decimate2x(input[0], input[1]); dBuffer[i] = dOut; dOut = ABS(dOut); if (dOut > dPeak) dPeak = dOut; } // normalize double dAmp = 1.0; if (dPeak > 0.0) dAmp = INT8_MAX / dPeak; for (uint32_t i = 0; i < length; i++) { double dSmp = dBuffer[i] * dAmp; // faster than calling round() if (dSmp < 0.0) dSmp -= 0.5; else if (dSmp > 0.0) dSmp += 0.5; buffer[i] = (int8_t)dSmp; } free(dBuffer); return true; } bool downsample2x16Bit(int16_t *buffer, uint32_t originalLength) { double *dBuffer = (double *)malloc(originalLength * sizeof (double)); if (dBuffer == NULL) return false; for (uint32_t i = 0; i < originalLength; i++) dBuffer[i] = buffer[i] * (1.0 / (INT16_MAX+1.0)); const double *input = dBuffer; double dPeak = 0.0; clearDownsamplerState(); const uint32_t length = originalLength / 2; for (uint32_t i = 0; i < length; i++, input += 2) { double dOut = decimate2x(input[0], input[1]); dBuffer[i] = dOut; dOut = ABS(dOut); if (dOut > dPeak) dPeak = dOut; } // normalize double dAmp = 1.0; if (dPeak > 0.0) dAmp = INT16_MAX / dPeak; for (uint32_t i = 0; i < length; i++) { double dSmp = dBuffer[i] * dAmp; // faster than calling round() if (dSmp < 0.0) dSmp -= 0.5; else if (dSmp > 0.0) dSmp += 0.5; buffer[i] = (int16_t)dSmp; } free(dBuffer); return true; } bool downsample2x32Bit(int32_t *buffer, uint32_t originalLength) { double *dBuffer = (double *)malloc(originalLength * sizeof (double)); if (dBuffer == NULL) return false; for (uint32_t i = 0; i < originalLength; i++) dBuffer[i] = buffer[i] * (1.0 / (INT32_MAX+1.0)); const double *input = dBuffer; double dPeak = 0.0; clearDownsamplerState(); const uint32_t length = originalLength / 2; for (uint32_t i = 0; i < length; i++, input += 2) { double dOut = decimate2x(input[0], input[1]); dBuffer[i] = dOut; dOut = ABS(dOut); if (dOut > dPeak) dPeak = dOut; } // normalize double dAmp = 1.0; if (dPeak > 0.0) dAmp = INT32_MAX / dPeak; for (uint32_t i = 0; i < length; i++) { double dSmp = dBuffer[i] * dAmp; // faster than calling round() if (dSmp < 0.0) dSmp -= 0.5; else if (dSmp > 0.0) dSmp += 0.5; buffer[i] = (int32_t)dSmp; } free(dBuffer); return true; }