/* * synth.c - The MPEG1 filter bank, algorithm straight from the * specification. * * This code is part of the Experimental Haskell MP3 Decoder, version 0.0.1. * Copyright (c) 2008 Bjorn Edstrom * */ #include #define PI 3.1415926535897931 static double synth_window[512] = { 0.000000000, -0.000015259, -0.000015259, -0.000015259, -0.000015259, -0.000015259, -0.000015259, -0.000030518, -0.000030518, -0.000030518, -0.000030518, -0.000045776, -0.000045776, -0.000061035, -0.000061035, -0.000076294, -0.000076294, -0.000091553, -0.000106812, -0.000106812, -0.000122070, -0.000137329, -0.000152588, -0.000167847, -0.000198364, -0.000213623, -0.000244141, -0.000259399, -0.000289917, -0.000320435, -0.000366211, -0.000396729, -0.000442505, -0.000473022, -0.000534058, -0.000579834, -0.000625610, -0.000686646, -0.000747681, -0.000808716, -0.000885010, -0.000961304, -0.001037598, -0.001113892, -0.001205444, -0.001296997, -0.001388550, -0.001480103, -0.001586914, -0.001693726, -0.001785278, -0.001907349, -0.002014160, -0.002120972, -0.002243042, -0.002349854, -0.002456665, -0.002578735, -0.002685547, -0.002792358, -0.002899170, -0.002990723, -0.003082275, -0.003173828, 0.003250122, 0.003326416, 0.003387451, 0.003433228, 0.003463745, 0.003479004, 0.003479004, 0.003463745, 0.003417969, 0.003372192, 0.003280640, 0.003173828, 0.003051758, 0.002883911, 0.002700806, 0.002487183, 0.002227783, 0.001937866, 0.001617432, 0.001266479, 0.000869751, 0.000442505, -0.000030518, -0.000549316, -0.001098633, -0.001693726, -0.002334595, -0.003005981, -0.003723145, -0.004486084, -0.005294800, -0.006118774, -0.007003784, -0.007919312, -0.008865356, -0.009841919, -0.010848999, -0.011886597, -0.012939453, -0.014022827, -0.015121460, -0.016235352, -0.017349243, -0.018463135, -0.019577026, -0.020690918, -0.021789551, -0.022857666, -0.023910522, -0.024932861, -0.025909424, -0.026840210, -0.027725220, -0.028533936, -0.029281616, -0.029937744, -0.030532837, -0.031005859, -0.031387329, -0.031661987, -0.031814575, -0.031845093, -0.031738281, -0.031478882, 0.031082153, 0.030517578, 0.029785156, 0.028884888, 0.027801514, 0.026535034, 0.025085449, 0.023422241, 0.021575928, 0.019531250, 0.017257690, 0.014801025, 0.012115479, 0.009231567, 0.006134033, 0.002822876, -0.000686646, -0.004394531, -0.008316040, -0.012420654, -0.016708374, -0.021179199, -0.025817871, -0.030609131, -0.035552979, -0.040634155, -0.045837402, -0.051132202, -0.056533813, -0.061996460, -0.067520142, -0.073059082, -0.078628540, -0.084182739, -0.089706421, -0.095169067, -0.100540161, -0.105819702, -0.110946655, -0.115921021, -0.120697021, -0.125259399, -0.129562378, -0.133590698, -0.137298584, -0.140670776, -0.143676758, -0.146255493, -0.148422241, -0.150115967, -0.151306152, -0.151962280, -0.152069092, -0.151596069, -0.150497437, -0.148773193, -0.146362305, -0.143264771, -0.139450073, -0.134887695, -0.129577637, -0.123474121, -0.116577148, -0.108856201, 0.100311279, 0.090927124, 0.080688477, 0.069595337, 0.057617188, 0.044784546, 0.031082153, 0.016510010, 0.001068115, -0.015228271, -0.032379150, -0.050354004, -0.069168091, -0.088775635, -0.109161377, -0.130310059, -0.152206421, -0.174789429, -0.198059082, -0.221984863, -0.246505737, -0.271591187, -0.297210693, -0.323318481, -0.349868774, -0.376800537, -0.404083252, -0.431655884, -0.459472656, -0.487472534, -0.515609741, -0.543823242, -0.572036743, -0.600219727, -0.628295898, -0.656219482, -0.683914185, -0.711318970, -0.738372803, -0.765029907, -0.791213989, -0.816864014, -0.841949463, -0.866363525, -0.890090942, -0.913055420, -0.935195923, -0.956481934, -0.976852417, -0.996246338, -1.014617920, -1.031936646, -1.048156738, -1.063217163, -1.077117920, -1.089782715, -1.101211548, -1.111373901, -1.120223999, -1.127746582, -1.133926392, -1.138763428, -1.142211914, -1.144287109, 1.144989014, 1.144287109, 1.142211914, 1.138763428, 1.133926392, 1.127746582, 1.120223999, 1.111373901, 1.101211548, 1.089782715, 1.077117920, 1.063217163, 1.048156738, 1.031936646, 1.014617920, 0.996246338, 0.976852417, 0.956481934, 0.935195923, 0.913055420, 0.890090942, 0.866363525, 0.841949463, 0.816864014, 0.791213989, 0.765029907, 0.738372803, 0.711318970, 0.683914185, 0.656219482, 0.628295898, 0.600219727, 0.572036743, 0.543823242, 0.515609741, 0.487472534, 0.459472656, 0.431655884, 0.404083252, 0.376800537, 0.349868774, 0.323318481, 0.297210693, 0.271591187, 0.246505737, 0.221984863, 0.198059082, 0.174789429, 0.152206421, 0.130310059, 0.109161377, 0.088775635, 0.069168091, 0.050354004, 0.032379150, 0.015228271, -0.001068115, -0.016510010, -0.031082153, -0.044784546, -0.057617188, -0.069595337, -0.080688477, -0.090927124, 0.100311279, 0.108856201, 0.116577148, 0.123474121, 0.129577637, 0.134887695, 0.139450073, 0.143264771, 0.146362305, 0.148773193, 0.150497437, 0.151596069, 0.152069092, 0.151962280, 0.151306152, 0.150115967, 0.148422241, 0.146255493, 0.143676758, 0.140670776, 0.137298584, 0.133590698, 0.129562378, 0.125259399, 0.120697021, 0.115921021, 0.110946655, 0.105819702, 0.100540161, 0.095169067, 0.089706421, 0.084182739, 0.078628540, 0.073059082, 0.067520142, 0.061996460, 0.056533813, 0.051132202, 0.045837402, 0.040634155, 0.035552979, 0.030609131, 0.025817871, 0.021179199, 0.016708374, 0.012420654, 0.008316040, 0.004394531, 0.000686646, -0.002822876, -0.006134033, -0.009231567, -0.012115479, -0.014801025, -0.017257690, -0.019531250, -0.021575928, -0.023422241, -0.025085449, -0.026535034, -0.027801514, -0.028884888, -0.029785156, -0.030517578, 0.031082153, 0.031478882, 0.031738281, 0.031845093, 0.031814575, 0.031661987, 0.031387329, 0.031005859, 0.030532837, 0.029937744, 0.029281616, 0.028533936, 0.027725220, 0.026840210, 0.025909424, 0.024932861, 0.023910522, 0.022857666, 0.021789551, 0.020690918, 0.019577026, 0.018463135, 0.017349243, 0.016235352, 0.015121460, 0.014022827, 0.012939453, 0.011886597, 0.010848999, 0.009841919, 0.008865356, 0.007919312, 0.007003784, 0.006118774, 0.005294800, 0.004486084, 0.003723145, 0.003005981, 0.002334595, 0.001693726, 0.001098633, 0.000549316, 0.000030518, -0.000442505, -0.000869751, -0.001266479, -0.001617432, -0.001937866, -0.002227783, -0.002487183, -0.002700806, -0.002883911, -0.003051758, -0.003173828, -0.003280640, -0.003372192, -0.003417969, -0.003463745, -0.003479004, -0.003479004, -0.003463745, -0.003433228, -0.003387451, -0.003326416, 0.003250122, 0.003173828, 0.003082275, 0.002990723, 0.002899170, 0.002792358, 0.002685547, 0.002578735, 0.002456665, 0.002349854, 0.002243042, 0.002120972, 0.002014160, 0.001907349, 0.001785278, 0.001693726, 0.001586914, 0.001480103, 0.001388550, 0.001296997, 0.001205444, 0.001113892, 0.001037598, 0.000961304, 0.000885010, 0.000808716, 0.000747681, 0.000686646, 0.000625610, 0.000579834, 0.000534058, 0.000473022, 0.000442505, 0.000396729, 0.000366211, 0.000320435, 0.000289917, 0.000259399, 0.000244141, 0.000213623, 0.000198364, 0.000167847, 0.000152588, 0.000137329, 0.000122070, 0.000106812, 0.000106812, 0.000091553, 0.000076294, 0.000076294, 0.000061035, 0.000061035, 0.000045776, 0.000045776, 0.000030518, 0.000030518, 0.000030518, 0.000030518, 0.000015259, 0.000015259, 0.000015259, 0.000015259, 0.000015259, 0.000015259, }; void synth(double state[1024], double samples[576], double newstate[1024], double output[576]) { double S[32], U[512]; static double lookup[64][32]; /* Initialize the lookup matrix */ for(int i = 0; i < 64; i++) { for(int j = 0; j < 32; j++) { lookup[i][j] = cos((16.0 + i) * (2.0*j + 1) * (PI/64.0)); } } /* Initialize the new state */ for(int i = 0; i < 1024; i++) { newstate[i] = state[i]; } /* Then start working */ for(int s = 0; s < 18; s++) { for(int i = 0; i < 32; i++) { S[i] = samples[i*18 + s]; } /* Calculate the new state */ for(int i = 1023; i > 63; i--) { newstate[i] = newstate[i - 64]; } for(int i = 0; i < 64; i++) { double sum = 0.0; for(int j = 0; j < 32; j++) { sum += S[j] * lookup[i][j]; } newstate[i] = sum; } /* Done calculating new state */ /* Start calculating output */ for(int i = 0; i < 8; i++) { for(int j = 0; j < 32; j++) { U[i*64 + j] = newstate[i*128 + j]; U[i*64 + j + 32] = newstate[i*128 + j + 96]; } } for(int i = 0; i < 512; i++) { U[i] *= synth_window[i]; } for(int i = 0; i < 32; i++) { double sum = 0.0; for(int j = 0; j < 16; j++) { sum += U[j*32 + i]; } output[32*s + i] = sum; } /* Done calculating output */ } return; }