48 lines
2.4 KiB
C
48 lines
2.4 KiB
C
#include "coding.h"
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/* Decodes SunPlus' ADPCM codec used on the Tiger Game.com.
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* Highly improved, optimised signed 16-bit version of the algorithm. */
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static const int16_t slope_table[8][16] =
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{
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{ 0, 0, 256, -256, 512, -512, 1024, -1024, 1536, -1536, 2048, -2048, 3072, -3072, 4096, -4096 },
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{ 256, -256, 768, -768, 1280, -1280, 2304, -2304, 3328, -3328, 4352, -4352, 6400, -6400, 8448, -8448 },
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{ 512, -512, 1280, -1280, 2048, -2048, 3584, -3584, 5120, -5120, 6656, -6656, 9728, -9728, 12800, -12800 },
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{ 768, -768, 1792, -1792, 2816, -2816, 4864, -4864, 6912, -6912, 8960, -8960, 10496, -10496, 17152, -17152 },
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{ 1024, -1024, 2304, -2304, 3584, -3584, 6144, -6144, 8704, -8704, 11264, -11264, 16384, -16384, 21504, -21504 },
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{ 1280, -1280, 2816, -2816, 4352, -4352, 7424, -7424, 10496, -10496, 13568, -13568, 19712, -19712, 28416, -28416 },
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{ 1536, -1536, 3328, -3328, 5120, -5120, 8704, -8704, 12288, -12288, 15872, -15872, 23040, -23040, 30208, -30208 },
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{ 1792, -1792, 3840, -3840, 5888, -5888, 9984, -9984, 14080, -14080, 18176, -18176, 26368, -26368, 32000, -32000 },
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};
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static const uint8_t next_step[8][16] =
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{
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{ 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 2, 2, 3, 3, 4, 4 },
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{ 0, 0, 0, 0, 1, 1, 1, 1, 3, 3, 3, 3, 4, 4, 5, 5 },
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{ 1, 1, 1, 1, 2, 2, 2, 2, 4, 4, 4, 4, 5, 5, 6, 6 },
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{ 2, 2, 2, 2, 3, 3, 3, 3, 5, 5, 5, 5, 6, 6, 7, 7 },
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{ 3, 3, 3, 3, 4, 4, 4, 4, 6, 6, 6, 6, 7, 7, 7, 7 },
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{ 4, 4, 4, 4, 5, 5, 5, 5, 7, 7, 7, 7, 7, 7, 7, 7 },
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{ 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7 },
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{ 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7 }
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};
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void decode_tgc(VGMSTREAMCHANNEL * stream, sample_t * outbuf, int32_t first_sample, int32_t samples_to_do)
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{
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for (int i = first_sample, sample_count = 0; i < first_sample + samples_to_do; i++, sample_count++)
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{
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uint8_t nibble = ((uint8_t)read_8bit(stream->offset + i/2, stream->streamfile) >>
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(i & 1 ? 4 : 0)) & 0xf;
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stream->adpcm_history1_32 += slope_table[stream->adpcm_step_index][nibble];
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stream->adpcm_step_index = next_step [stream->adpcm_step_index][nibble];
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if (stream->adpcm_history1_32 < -32768)
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stream->adpcm_history1_32 = -32768;
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if (stream->adpcm_history1_32 > 32767)
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stream->adpcm_history1_32 = 32767;
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outbuf[sample_count] = (sample_t)stream->adpcm_history1_32;
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}
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}
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