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https://github.com/vgmstream/vgmstream.git
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53 lines
1.5 KiB
C
53 lines
1.5 KiB
C
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#include "coding.h"
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#include "../util.h"
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/* lsf ADPCM, as seen in Fastlane Street Racing */
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static const short lsf_coefs[5][2] = {
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{0x73, -0x34},
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{0, 0},
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{0x62, -0x37},
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{0x3C, 0},
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{0x7A, -0x3c}
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};
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void decode_lsf(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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const int bytes_per_frame = 0x1c;
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const int samples_per_frame = (bytes_per_frame-1)*2;
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int framesin = first_sample/samples_per_frame;
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uint8_t q = 0xFF - read_8bit(framesin*bytes_per_frame + stream->offset,stream->streamfile);
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int scale = (q&0xF0)>>4;
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int coef_idx = q&0x0F;
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int32_t hist1 = stream->adpcm_history1_16;
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int32_t hist2 = stream->adpcm_history2_16;
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first_sample = first_sample%samples_per_frame;
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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_byte = read_8bit(framesin*bytes_per_frame+stream->offset+1+i/2,stream->streamfile);
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long prediction =
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(hist1 * lsf_coefs[coef_idx][0] +
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hist2 * lsf_coefs[coef_idx][1]) / 0x40;
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prediction += (i&1?
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get_high_nibble_signed(sample_byte):
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get_low_nibble_signed(sample_byte)
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) * (1 << (12-scale));
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prediction = clamp16(prediction);
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hist2 = hist1;
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hist1 = prediction;
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outbuf[sample_count] = prediction;
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}
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stream->adpcm_history1_16 = hist1;
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stream->adpcm_history2_16 = hist2;
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}
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