diff --git a/src/audio_core/CMakeLists.txt b/src/audio_core/CMakeLists.txt
index 81121167d6..05a61b5cd4 100644
--- a/src/audio_core/CMakeLists.txt
+++ b/src/audio_core/CMakeLists.txt
@@ -4,6 +4,8 @@ add_library(audio_core STATIC
buffer.h
cubeb_sink.cpp
cubeb_sink.h
+ codec.cpp
+ codec.h
null_sink.h
stream.cpp
stream.h
diff --git a/src/audio_core/codec.cpp b/src/audio_core/codec.cpp
new file mode 100644
index 0000000000..c3021403f5
--- /dev/null
+++ b/src/audio_core/codec.cpp
@@ -0,0 +1,77 @@
+// 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, 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 size_t FRAME_LEN = 8;
+ constexpr 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 size_t sample_count = (size / FRAME_LEN) * SAMPLES_PER_FRAME;
+ const 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 size_t NUM_FRAMES =
+ (sample_count + (SAMPLES_PER_FRAME - 1)) / SAMPLES_PER_FRAME; // Round up.
+ for (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);
+ };
+
+ size_t outputi = framei * SAMPLES_PER_FRAME;
+ size_t datai = framei * FRAME_LEN + 1;
+ for (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
diff --git a/src/audio_core/codec.h b/src/audio_core/codec.h
new file mode 100644
index 0000000000..3f845c42c3
--- /dev/null
+++ b/src/audio_core/codec.h
@@ -0,0 +1,44 @@
+// Copyright 2018 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <array>
+#include <vector>
+
+#include "common/common_types.h"
+
+namespace AudioCore::Codec {
+
+enum class PcmFormat : u32 {
+ Invalid = 0,
+ Int8 = 1,
+ Int16 = 2,
+ Int24 = 3,
+ Int32 = 4,
+ PcmFloat = 5,
+ Adpcm = 6,
+};
+
+/// See: Codec::DecodeADPCM
+struct ADPCMState {
+ // Two historical samples from previous processed buffer,
+ // required for ADPCM decoding
+ s16 yn1; ///< y[n-1]
+ s16 yn2; ///< y[n-2]
+};
+
+using ADPCM_Coeff = std::array<s16, 16>;
+
+/**
+ * @param data Pointer to buffer that contains ADPCM data to decode
+ * @param size Size of buffer in bytes
+ * @param coeff ADPCM coefficients
+ * @param state ADPCM state, this is updated with new state
+ * @return Decoded stereo signed PCM16 data, sample_count in length
+ */
+std::vector<s16> DecodeADPCM(const u8* const data, size_t size, const ADPCM_Coeff& coeff,
+ ADPCMState& state);
+
+}; // namespace AudioCore::Codec
diff --git a/src/core/hle/service/audio/audout_u.cpp b/src/core/hle/service/audio/audout_u.cpp
index 9f4c7855a5..f4a5576343 100644
--- a/src/core/hle/service/audio/audout_u.cpp
+++ b/src/core/hle/service/audio/audout_u.cpp
@@ -4,6 +4,8 @@
#include <array>
#include <vector>
+
+#include "audio_core/codec.h"
#include "common/logging/log.h"
#include "core/core.h"
#include "core/hle/ipc_helpers.h"
@@ -200,7 +202,7 @@ void AudOutU::OpenAudioOutImpl(Kernel::HLERequestContext& ctx) {
rb.Push(RESULT_SUCCESS);
rb.Push<u32>(DefaultSampleRate);
rb.Push<u32>(params.channel_count);
- rb.Push<u32>(static_cast<u32>(PcmFormat::Int16));
+ rb.Push<u32>(static_cast<u32>(AudioCore::Codec::PcmFormat::Int16));
rb.Push<u32>(static_cast<u32>(AudioState::Stopped));
rb.PushIpcInterface<Audio::IAudioOut>(audio_out_interface);
}
diff --git a/src/core/hle/service/audio/audout_u.h b/src/core/hle/service/audio/audout_u.h
index e5c2184d58..fd491f65d7 100644
--- a/src/core/hle/service/audio/audout_u.h
+++ b/src/core/hle/service/audio/audout_u.h
@@ -38,16 +38,6 @@ private:
void ListAudioOutsImpl(Kernel::HLERequestContext& ctx);
void OpenAudioOutImpl(Kernel::HLERequestContext& ctx);
-
- enum class PcmFormat : u32 {
- Invalid = 0,
- Int8 = 1,
- Int16 = 2,
- Int24 = 3,
- Int32 = 4,
- PcmFloat = 5,
- Adpcm = 6,
- };
};
} // namespace Service::Audio