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58 lines
1.7 KiB
C++
58 lines
1.7 KiB
C++
#include "sound_decoder.hpp"
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static const int IndexTable[] =
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{
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-1, -1, -1, -1, 2, 4, 6, 8,
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-1, -1, -1, -1, 2, 4, 6, 8,
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};
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static const int ADPCM_STEP_TABLE[] =
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{
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7, 8, 9, 10, 11, 12, 13, 14, 16, 17,
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19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
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50, 55, 60, 66, 73, 80, 88, 97, 107, 118,
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130, 143, 157, 173, 190, 209, 230, 253, 279, 307,
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337, 371, 408, 449, 494, 544, 598, 658, 724, 796,
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876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066,
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2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358,
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5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
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15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767, 0
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};
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constexpr int clamp(int n, int l, int h) { return n <= l ? l : n >= h ? h : n; }
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#include "DSC"
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// thxx RinLovesYou (https://github.com/miso-xyz/PPMLib/blob/c7548bf4cdb0e368af552c71a45eb9f96f2e3385/PPMLib/Extensions/AdpcmDecoder.cs#L46-L119)
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void SoundDecoder::ADPCM2PCM16(const char* src, short* dst, int srclen)
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{
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int sample = 0;
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int step_index = 0;
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int predictor = 0;
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bool lowNibble = true;
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for(srclen*=2;srclen--;)
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{
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// switch between high and low nibble each loop iteration
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// increments srcPtr after every high nibble
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if (lowNibble)
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sample = (*src) & 0xF;
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else
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sample = (*(src++)) >> 4;
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lowNibble = !lowNibble;
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int step = ADPCM_STEP_TABLE[step_index];
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int diff = step >> 3;
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if ((sample & 1) != 0) diff += step >> 2;
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if ((sample & 2) != 0) diff += step >> 1;
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if ((sample & 4) != 0) diff += step;
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if ((sample & 8) != 0) diff = -diff;
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predictor += diff;
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predictor = clamp(predictor, -32768, 32767);
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step_index += IndexTable[sample];
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step_index = clamp(step_index, 0, 88);
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*(dst++) = (short)predictor;
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}
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} |