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Melefo
66 lines
1.5 KiB
C++
66 lines
1.5 KiB
C++
//
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// Created by melefo on 2/3/21.
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//
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#include <algorithm>
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#include "DSP.hpp"
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namespace ComSquare::APU::DSP
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{
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void DSP::decodeBRR(Voice &voice)
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{
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int32_t value = this->_brr.value << 8 | this->_readRAM(voice.brrAddress + voice.brrOffset + 1);
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int32_t filter = this->_brr.header >> 2 & 0b11;
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int32_t range = this->_brr.header >> 4 & 0b1111;
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for (int i = 0; i < 4; i++) {
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int32_t sample = value >> 12;
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value <<= 4;
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if (range <= 12) {
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sample <<= range;
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sample >>= 1;
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}
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else
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sample &= ~0x7FF;
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int offset = voice.sampleOffset;
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int lastSample;
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int afterLastSample;
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if (--offset < 0)
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offset = 11;
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lastSample = voice.samples[offset];
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if (--offset < 0)
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offset = 11;
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afterLastSample = voice.samples[offset];
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switch (filter) {
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case 0:
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break;
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case 1:
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sample += lastSample;
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sample += (lastSample) >> 4;
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break;
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case 2:
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sample += lastSample << 1;
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sample += -((lastSample << 1) + lastSample) >> 5;
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sample -= afterLastSample;
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sample += afterLastSample >> 4;
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break;
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case 3:
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sample += lastSample << 1;
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sample += -(lastSample + (lastSample << 2) + (lastSample << 3)) >> 6;
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sample -= afterLastSample;
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sample += ((afterLastSample << 1) + afterLastSample) >> 4;
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break;
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}
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sample = std::clamp(sample, 0, 16);
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sample <<= 1;
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voice.samples[voice.sampleOffset] = sample;
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if (++voice.sampleOffset >= 12)
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voice.sampleOffset = 0;
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}
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}
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} |