8 files changed, 179 insertions, 3 deletions

diff --git a/src/audio_core/CMakeLists.txt b/src/audio_core/CMakeLists.txt
index 4cd7aba67..13b5e400e 100644
--- a/src/audio_core/CMakeLists.txt
+++ b/src/audio_core/CMakeLists.txt
@@ -25,7 +25,18 @@ set(HEADERS
 
 include_directories(../../externals/soundtouch/include)
 
+if(SDL2_FOUND)
+    set(SRCS ${SRCS} sdl2_sink.cpp)
+    set(HEADERS ${HEADERS} sdl2_sink.h)
+    include_directories(${SDL2_INCLUDE_DIR})
+endif()
+
 create_directory_groups(${SRCS} ${HEADERS})
 
 add_library(audio_core STATIC ${SRCS} ${HEADERS})
 target_link_libraries(audio_core SoundTouch)
+
+if(SDL2_FOUND)
+    target_link_libraries(audio_core ${SDL2_LIBRARY})
+    set_property(TARGET audio_core APPEND PROPERTY COMPILE_DEFINITIONS HAVE_SDL2)
+endif()
diff --git a/src/audio_core/sdl2_sink.cpp b/src/audio_core/sdl2_sink.cpp
new file mode 100644
index 000000000..dc75c04ee
--- /dev/null
+++ b/src/audio_core/sdl2_sink.cpp
@@ -0,0 +1,126 @@
+// Copyright 2016 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <list>
+#include <vector>
+
+#include <SDL.h>
+
+#include "audio_core/audio_core.h"
+#include "audio_core/sdl2_sink.h"
+
+#include "common/assert.h"
+#include "common/logging/log.h"
+#include <numeric>
+
+namespace AudioCore {
+
+struct SDL2Sink::Impl {
+    unsigned int sample_rate = 0;
+
+    SDL_AudioDeviceID audio_device_id = 0;
+
+    std::list<std::vector<s16>> queue;
+
+    static void Callback(void* impl_, u8* buffer, int buffer_size_in_bytes);
+};
+
+SDL2Sink::SDL2Sink() : impl(std::make_unique<Impl>()) {
+    if (SDL_Init(SDL_INIT_AUDIO) < 0) {
+        LOG_CRITICAL(Audio_Sink, "SDL_Init(SDL_INIT_AUDIO) failed");
+        impl->audio_device_id = 0;
+        return;
+    }
+
+    SDL_AudioSpec desired_audiospec;
+    SDL_zero(desired_audiospec);
+    desired_audiospec.format = AUDIO_S16;
+    desired_audiospec.channels = 2;
+    desired_audiospec.freq = native_sample_rate;
+    desired_audiospec.samples = 1024;
+    desired_audiospec.userdata = impl.get();
+    desired_audiospec.callback = &Impl::Callback;
+
+    SDL_AudioSpec obtained_audiospec;
+    SDL_zero(obtained_audiospec);
+
+    impl->audio_device_id = SDL_OpenAudioDevice(nullptr, false, &desired_audiospec, &obtained_audiospec, 0);
+    if (impl->audio_device_id <= 0) {
+        LOG_CRITICAL(Audio_Sink, "SDL_OpenAudioDevice failed");
+        return;
+    }
+
+    impl->sample_rate = obtained_audiospec.freq;
+
+    // SDL2 audio devices start out paused, unpause it:
+    SDL_PauseAudioDevice(impl->audio_device_id, 0);
+}
+
+SDL2Sink::~SDL2Sink() {
+    if (impl->audio_device_id <= 0)
+        return;
+
+    SDL_CloseAudioDevice(impl->audio_device_id);
+}
+
+unsigned int SDL2Sink::GetNativeSampleRate() const {
+    if (impl->audio_device_id <= 0)
+        return native_sample_rate;
+
+    return impl->sample_rate;
+}
+
+void SDL2Sink::EnqueueSamples(const std::vector<s16>& samples) {
+    if (impl->audio_device_id <= 0)
+        return;
+
+    ASSERT_MSG(samples.size() % 2 == 0, "Samples must be in interleaved stereo PCM16 format (size must be a multiple of two)");
+
+    SDL_LockAudioDevice(impl->audio_device_id);
+    impl->queue.emplace_back(samples);
+    SDL_UnlockAudioDevice(impl->audio_device_id);
+}
+
+size_t SDL2Sink::SamplesInQueue() const {
+    if (impl->audio_device_id <= 0)
+        return 0;
+
+    SDL_LockAudioDevice(impl->audio_device_id);
+
+    size_t total_size = std::accumulate(impl->queue.begin(), impl->queue.end(), static_cast<size_t>(0),
+        [](size_t sum, const auto& buffer) {
+            // Division by two because each stereo sample is made of two s16.
+            return sum + buffer.size() / 2;
+        });
+
+    SDL_UnlockAudioDevice(impl->audio_device_id);
+
+    return total_size;
+}
+
+void SDL2Sink::Impl::Callback(void* impl_, u8* buffer, int buffer_size_in_bytes) {
+    Impl* impl = reinterpret_cast<Impl*>(impl_);
+
+    size_t remaining_size = static_cast<size_t>(buffer_size_in_bytes) / sizeof(s16); // Keep track of size in 16-bit increments.
+
+    while (remaining_size > 0 && !impl->queue.empty()) {
+        if (impl->queue.front().size() <= remaining_size) {
+            memcpy(buffer, impl->queue.front().data(), impl->queue.front().size() * sizeof(s16));
+            buffer += impl->queue.front().size() * sizeof(s16);
+            remaining_size -= impl->queue.front().size();
+            impl->queue.pop_front();
+        } else {
+            memcpy(buffer, impl->queue.front().data(), remaining_size * sizeof(s16));
+            buffer += remaining_size * sizeof(s16);
+            impl->queue.front().erase(impl->queue.front().begin(), impl->queue.front().begin() + remaining_size);
+            remaining_size = 0;
+        }
+    }
+
+    if (remaining_size > 0) {
+        memset(buffer, 0, remaining_size * sizeof(s16));
+    }
+}
+
+} // namespace AudioCore
diff --git a/src/audio_core/sdl2_sink.h b/src/audio_core/sdl2_sink.h
new file mode 100644
index 000000000..0f296b673
--- /dev/null
+++ b/src/audio_core/sdl2_sink.h
@@ -0,0 +1,30 @@
+// Copyright 2016 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <cstddef>
+#include <memory>
+
+#include "audio_core/sink.h"
+
+namespace AudioCore {
+
+class SDL2Sink final : public Sink {
+public:
+    SDL2Sink();
+    ~SDL2Sink() override;
+
+    unsigned int GetNativeSampleRate() const override;
+
+    void EnqueueSamples(const std::vector<s16>& samples) override;
+
+    size_t SamplesInQueue() const override;
+
+private:
+    struct Impl;
+    std::unique_ptr<Impl> impl;
+};
+
+} // namespace AudioCore
diff --git a/src/audio_core/sink.h b/src/audio_core/sink.h
index cad21a85e..1c881c3d2 100644
--- a/src/audio_core/sink.h
+++ b/src/audio_core/sink.h
@@ -19,7 +19,7 @@ public:
     virtual ~Sink() = default;
 
     /// The native rate of this sink. The sink expects to be fed samples that respect this. (Units: samples/sec)
-    virtual unsigned GetNativeSampleRate() const = 0;
+    virtual unsigned int GetNativeSampleRate() const = 0;
 
     /**
      * Feed stereo samples to sink.
diff --git a/src/audio_core/sink_details.cpp b/src/audio_core/sink_details.cpp
index d2cc74103..ba5e83d17 100644
--- a/src/audio_core/sink_details.cpp
+++ b/src/audio_core/sink_details.cpp
@@ -8,10 +8,17 @@
 #include "audio_core/null_sink.h"
 #include "audio_core/sink_details.h"
 
+#ifdef HAVE_SDL2
+#include "audio_core/sdl2_sink.h"
+#endif
+
 namespace AudioCore {
 
 // g_sink_details is ordered in terms of desirability, with the best choice at the top.
 const std::vector<SinkDetails> g_sink_details = {
+#ifdef HAVE_SDL2
+    { "sdl2", []() { return std::make_unique<SDL2Sink>(); } },
+#endif
     { "null", []() { return std::make_unique<NullSink>(); } },
 };
 
diff --git a/src/citra/default_ini.h b/src/citra/default_ini.h
index 0e6171736..49126356f 100644
--- a/src/citra/default_ini.h
+++ b/src/citra/default_ini.h
@@ -58,7 +58,7 @@ bg_green =
 
 [Audio]
 # Which audio output engine to use.
-# auto (default): Auto-select, null: No audio output
+# auto (default): Auto-select, null: No audio output, sdl2: SDL2 (if available)
 output_engine =
 
 [Data Storage]
diff --git a/src/common/logging/backend.cpp b/src/common/logging/backend.cpp
index 3d39f94d5..d7008fc66 100644
--- a/src/common/logging/backend.cpp
+++ b/src/common/logging/backend.cpp
@@ -65,6 +65,7 @@ namespace Log {
         SUB(Render, OpenGL) \
         CLS(Audio) \
         SUB(Audio, DSP) \
+        SUB(Audio, Sink) \
         CLS(Loader)
 
 // GetClassName is a macro defined by Windows.h, grrr...
diff --git a/src/common/logging/log.h b/src/common/logging/log.h
index 521362317..c6910b1c7 100644
--- a/src/common/logging/log.h
+++ b/src/common/logging/log.h
@@ -78,8 +78,9 @@ enum class Class : ClassType {
     Render,                     ///< Emulator video output and hardware acceleration
     Render_Software,            ///< Software renderer backend
     Render_OpenGL,              ///< OpenGL backend
-    Audio,                      ///< Emulator audio output
+    Audio,                      ///< Audio emulation
     Audio_DSP,                  ///< The HLE implementation of the DSP
+    Audio_Sink,                 ///< Emulator audio output backend
     Loader,                     ///< ROM loader
 
     Count ///< Total number of logging classes