mirror of
https://git.suyu.dev/suyu/suyu.git
synced 2024-11-15 11:22:44 +01:00
77 lines
2.8 KiB
C++
77 lines
2.8 KiB
C++
// Copyright 2018 yuzu Emulator Project
|
|
// Licensed under GPLv2 or any later version
|
|
// Refer to the license.txt file included.
|
|
|
|
#include <algorithm>
|
|
|
|
#include "audio_core/codec.h"
|
|
|
|
namespace AudioCore::Codec {
|
|
|
|
std::vector<s16> DecodeADPCM(const u8* const data, std::size_t size, const ADPCM_Coeff& coeff,
|
|
ADPCMState& state) {
|
|
// GC-ADPCM with scale factor and variable coefficients.
|
|
// Frames are 8 bytes long containing 14 samples each.
|
|
// Samples are 4 bits (one nibble) long.
|
|
|
|
constexpr std::size_t FRAME_LEN = 8;
|
|
constexpr std::size_t SAMPLES_PER_FRAME = 14;
|
|
constexpr std::array<int, 16> SIGNED_NIBBLES = {
|
|
{0, 1, 2, 3, 4, 5, 6, 7, -8, -7, -6, -5, -4, -3, -2, -1}};
|
|
|
|
const std::size_t sample_count = (size / FRAME_LEN) * SAMPLES_PER_FRAME;
|
|
const std::size_t ret_size =
|
|
sample_count % 2 == 0 ? sample_count : sample_count + 1; // Ensure multiple of two.
|
|
std::vector<s16> ret(ret_size);
|
|
|
|
int yn1 = state.yn1, yn2 = state.yn2;
|
|
|
|
const std::size_t NUM_FRAMES =
|
|
(sample_count + (SAMPLES_PER_FRAME - 1)) / SAMPLES_PER_FRAME; // Round up.
|
|
for (std::size_t framei = 0; framei < NUM_FRAMES; framei++) {
|
|
const int frame_header = data[framei * FRAME_LEN];
|
|
const int scale = 1 << (frame_header & 0xF);
|
|
const int idx = (frame_header >> 4) & 0x7;
|
|
|
|
// Coefficients are fixed point with 11 bits fractional part.
|
|
const int coef1 = coeff[idx * 2 + 0];
|
|
const int coef2 = coeff[idx * 2 + 1];
|
|
|
|
// Decodes an audio sample. One nibble produces one sample.
|
|
const auto decode_sample = [&](const int nibble) -> s16 {
|
|
const int xn = nibble * scale;
|
|
// We first transform everything into 11 bit fixed point, perform the second order
|
|
// digital filter, then transform back.
|
|
// 0x400 == 0.5 in 11 bit fixed point.
|
|
// Filter: y[n] = x[n] + 0.5 + c1 * y[n-1] + c2 * y[n-2]
|
|
int val = ((xn << 11) + 0x400 + coef1 * yn1 + coef2 * yn2) >> 11;
|
|
// Clamp to output range.
|
|
val = std::clamp<s32>(val, -32768, 32767);
|
|
// Advance output feedback.
|
|
yn2 = yn1;
|
|
yn1 = val;
|
|
return static_cast<s16>(val);
|
|
};
|
|
|
|
std::size_t outputi = framei * SAMPLES_PER_FRAME;
|
|
std::size_t datai = framei * FRAME_LEN + 1;
|
|
for (std::size_t i = 0; i < SAMPLES_PER_FRAME && outputi < sample_count; i += 2) {
|
|
const s16 sample1 = decode_sample(SIGNED_NIBBLES[data[datai] >> 4]);
|
|
ret[outputi] = sample1;
|
|
outputi++;
|
|
|
|
const s16 sample2 = decode_sample(SIGNED_NIBBLES[data[datai] & 0xF]);
|
|
ret[outputi] = sample2;
|
|
outputi++;
|
|
|
|
datai++;
|
|
}
|
|
}
|
|
|
|
state.yn1 = yn1;
|
|
state.yn2 = yn2;
|
|
|
|
return ret;
|
|
}
|
|
|
|
} // namespace AudioCore::Codec
|