53 lines
1.7 KiB
C++
53 lines
1.7 KiB
C++
// SPDX-License-Identifier: MPL-2.0
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// Copyright © 2020 Skyline Team and Contributors (https://github.com/skyline-emu/)
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#include "common.h"
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#include "adpcm_decoder.h"
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namespace skyline::audio {
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AdpcmDecoder::AdpcmDecoder(std::vector<std::array<i16, 2>> coefficients) : coefficients(std::move(coefficients)) {}
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std::vector<i16> AdpcmDecoder::Decode(span<u8> adpcmData) {
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constexpr size_t BytesPerFrame{0x8};
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constexpr size_t SamplesPerFrame{0xE};
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size_t remainingSamples{(adpcmData.size() / BytesPerFrame) * SamplesPerFrame};
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std::vector<i16> output;
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output.reserve(remainingSamples);
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size_t inputOffset{};
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while (inputOffset < adpcmData.size()) {
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FrameHeader header{adpcmData[inputOffset++]};
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size_t frameSamples{std::min(SamplesPerFrame, remainingSamples)};
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i32 ctx{};
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for (size_t index{}; index < frameSamples; index++) {
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i32 sample{};
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if (index & 1) {
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sample = (ctx << 28) >> 28;
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} else {
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ctx = adpcmData[inputOffset++];
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sample = (ctx << 24) >> 28;
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}
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i32 prediction{history[0] * coefficients[header.coefficientIndex][0] + history[1] * coefficients[header.coefficientIndex][1]};
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sample = (sample * (0x800 << header.scale) + prediction + 0x400) >> 11;
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auto saturated{audio::Saturate<i16, i32>(sample)};
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output.push_back(saturated);
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history[1] = history[0];
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history[0] = saturated;
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}
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remainingSamples -= frameSamples;
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}
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return output;
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}
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}
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