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https://github.com/vgmstream/vgmstream.git
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65 lines
2.4 KiB
C
65 lines
2.4 KiB
C
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#include "coding.h"
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/* Decodec Argonaut's ASF ADPCM codec. Algorithm follows Croc2_asf2raw.exe, and the waveform
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* looks almost correct, but should reverse engineer asfcodec.adl (DLL) for accuracy. */
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void decode_asf(VGMSTREAMCHANNEL * stream, sample * outbuf, int channelspacing, int32_t first_sample, int32_t samples_to_do) {
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off_t frame_offset;
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int i, frames_in, sample_count = 0;
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size_t bytes_per_frame, samples_per_frame;
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uint32_t shift, mode;
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int32_t hist1 = stream->adpcm_history1_32;
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int32_t hist2 = stream->adpcm_history2_32;
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/* external interleave (fixed size), mono */
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bytes_per_frame = 0x11;
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samples_per_frame = (bytes_per_frame - 0x01) * 2;
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frames_in = first_sample / samples_per_frame;
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first_sample = first_sample % samples_per_frame;
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/* parse header */
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frame_offset = stream->offset + bytes_per_frame*frames_in;
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shift = (read_8bit(frame_offset+0x00,stream->streamfile) >> 4) & 0xf;
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mode = (read_8bit(frame_offset+0x00,stream->streamfile) >> 0) & 0xf;
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/* decoder nibbles */
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for (i = first_sample; i < first_sample + samples_to_do; i++) {
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int32_t new_sample;
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uint8_t nibbles = (uint8_t)read_8bit(frame_offset+0x01 + i/2,stream->streamfile);
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new_sample = i&1 ? /* high nibble first */
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get_low_nibble_signed(nibbles):
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get_high_nibble_signed(nibbles);
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new_sample = new_sample << shift;
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switch(mode) {
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case 0x00:
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new_sample = new_sample + hist1;
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//new_sample = (new_sample + (hist1 << 6)) >> 6; /* maybe? */
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break;
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case 0x04:
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new_sample = new_sample + hist1*2 - hist2;
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//new_sample = (new_sample + (hist1 << 7) - (hist2 << 6)) >> 6; /* maybe? */
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break;
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default: /* other modes (ex 0x02/09) seem only at last frame as 0 */
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//VGM_LOG("ASF: unknown mode %x at %lx\n", mode,frame_offset);
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//new_sample = 0; /* maybe? */
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break;
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}
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//new_sample = clamp16(new_sample); /* must not */
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new_sample = new_sample & 0xFFFF; /* probably unnecessary */
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outbuf[sample_count] = new_sample;
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sample_count += channelspacing;
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hist2 = hist1;
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hist1 = new_sample;
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}
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stream->adpcm_history1_32 = hist1;
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stream->adpcm_history2_32 = hist2;
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}
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