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https://github.com/vgmstream/vgmstream.git
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66 lines
2.0 KiB
C
66 lines
2.0 KiB
C
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#include "../util.h"
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#include "ima_decoder.h"
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const int32_t ADPCMTable[89] =
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{
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7, 8, 9, 10, 11, 12, 13, 14,
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16, 17, 19, 21, 23, 25, 28, 31,
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34, 37, 41, 45, 50, 55, 60, 66,
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73, 80, 88, 97, 107, 118, 130, 143,
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157, 173, 190, 209, 230, 253, 279, 307,
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337, 371, 408, 449, 494, 544, 598, 658,
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724, 796, 876, 963, 1060, 1166, 1282, 1411,
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1552, 1707, 1878, 2066, 2272, 2499, 2749, 3024,
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3327, 3660, 4026, 4428, 4871, 5358, 5894, 6484,
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7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
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15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794,
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32767
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};
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const int IMA_IndexTable[16] =
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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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void decode_nds_ima(VGMSTREAMCHANNEL * stream, sample * outbuf, int channelspacing, int32_t first_sample, int32_t samples_to_do) {
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int i=first_sample;
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int32_t sample_count;
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int32_t hist1 = stream->adpcm_history1_16;
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int step_index = stream->adpcm_step_index;
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if (first_sample==0) {
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step_index = read_16bitLE(stream->offset+2,stream->streamfile);
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hist1 = read_16bitLE(stream->offset,stream->streamfile);
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}
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for (i=first_sample,sample_count=0; i<first_sample+samples_to_do; i++,sample_count+=channelspacing) {
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int sample_nibble =
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(read_8bit(stream->offset+4+i/2,stream->streamfile) >> (i&1?4:0))&0xf;
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int delta;
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int step = ADPCMTable[step_index];
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delta = step >> 3;
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if (sample_nibble & 1) delta += step >> 2;
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if (sample_nibble & 2) delta += step >> 1;
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if (sample_nibble & 4) delta += step;
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if (sample_nibble & 8)
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outbuf[sample_count] = clamp16(hist1 - delta);
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else
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outbuf[sample_count] = clamp16(hist1 + delta);
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step_index += IMA_IndexTable[sample_nibble];
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if (step_index < 0) step_index=0;
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if (step_index > 88) step_index=88;
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hist1 = outbuf[sample_count];
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}
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stream->adpcm_history1_16 = hist1;
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stream->adpcm_step_index = step_index;
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}
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