[APU/Linux] Implement cross platform audio using SDL2 library.

src/xenia/apu/sdl/sdl_audio_driver.cc

@@ -0,0 +1,147 @@
+/**
+ ******************************************************************************
+ * Xenia : Xbox 360 Emulator Research Project                                 *
+ ******************************************************************************
+ * Copyright 2020 Ben Vanik. All rights reserved.                             *
+ * Released under the BSD license - see LICENSE in the root for more details. *
+ ******************************************************************************
+ */
+
+#include "xenia/apu/sdl/sdl_audio_driver.h"
+
+#include <array>
+
+#include "xenia/apu/apu_flags.h"
+#include "xenia/base/logging.h"
+#if XE_PLATFORM_WIN32
+#include "xenia/base/platform_win.h"
+#endif  // XE_PLATFORM_WIN32
+
+namespace xe {
+namespace apu {
+namespace sdl {
+
+SDLAudioDriver::SDLAudioDriver(Memory* memory,
+                               xe::threading::Semaphore* semaphore)
+    : AudioDriver(memory), semaphore_(semaphore) {}
+
+SDLAudioDriver::~SDLAudioDriver() {
+  assert_true(frames_queued_.empty());
+  assert_true(frames_unused_.empty());
+};
+
+bool SDLAudioDriver::Initialize() {
+  // With msvc delayed loading, exceptions are used to determine dll presence.
+#if XE_PLATFORM_WIN32
+  __try {
+#endif  // XE_PLATFORM_WIN32
+    SDL_version ver = {};
+    SDL_GetVersion(&ver);
+    if ((ver.major < 2) ||
+        (ver.major == 2 && ver.minor == 0 && ver.patch < 8)) {
+      XELOGW(
+          "SDL library version %d.%d.%d is outdated. "
+          "You may experience choppy audio.",
+          ver.major, ver.minor, ver.patch);
+    }
+#if XE_PLATFORM_WIN32
+  } __except (EXCEPTION_EXECUTE_HANDLER) {
+    return false;
+  }
+#endif  // XE_PLATFORM_WIN32
+
+  if (SDL_InitSubSystem(SDL_INIT_AUDIO) < 0) {
+    return false;
+  }
+  sdl_initialized_ = true;
+
+  SDL_AudioCallback audio_callback = [](void* userdata, Uint8* stream,
+                                        int len) -> void {
+    assert_true(len == frame_size_);
+    const auto driver = static_cast<SDLAudioDriver*>(userdata);
+
+    std::unique_lock<std::mutex> guard(driver->frames_mutex_);
+    if (driver->frames_queued_.empty()) {
+      memset(stream, 0, len);
+    } else {
+      auto buffer = driver->frames_queued_.front();
+      driver->frames_queued_.pop();
+      if (cvars::mute) {
+        memset(stream, 0, len);
+      } else {
+        memcpy(stream, buffer, len);
+      }
+      driver->frames_unused_.push(buffer);
+
+      auto ret = driver->semaphore_->Release(1, nullptr);
+      assert_true(ret);
+    }
+  };
+
+  SDL_AudioSpec wanted_spec = {};
+  wanted_spec.freq = frame_frequency_;
+  wanted_spec.format = AUDIO_F32;
+  wanted_spec.channels = frame_channels_;
+  wanted_spec.samples = channel_samples_;
+  wanted_spec.callback = audio_callback;
+  wanted_spec.userdata = this;
+  sdl_device_id_ = SDL_OpenAudioDevice(nullptr, 0, &wanted_spec, nullptr, 0);
+  if (sdl_device_id_ <= 0) {
+    XELOGE("SDL_OpenAudioDevice() failed.");
+    return false;
+  }
+  SDL_PauseAudioDevice(sdl_device_id_, 0);
+
+  return true;
+}
+
+void SDLAudioDriver::SubmitFrame(uint32_t frame_ptr) {
+  const auto input_frame = memory_->TranslateVirtual<float*>(frame_ptr);
+  float* output_frame;
+  {
+    std::unique_lock<std::mutex> guard(frames_mutex_);
+    if (frames_unused_.empty()) {
+      output_frame = new float[frame_samples_];
+    } else {
+      output_frame = frames_unused_.top();
+      frames_unused_.pop();
+    }
+  }
+
+  // interleave the data
+  for (size_t index = 0, o = 0; index < channel_samples_; ++index) {
+    for (size_t channel = 0, table = 0; channel < frame_channels_;
+         ++channel, table += channel_samples_) {
+      output_frame[o++] = xe::byte_swap(input_frame[table + index]);
+    }
+  }
+
+  {
+    std::unique_lock<std::mutex> guard(frames_mutex_);
+    frames_queued_.push(output_frame);
+  }
+}
+
+void SDLAudioDriver::Shutdown() {
+  if (sdl_device_id_ > 0) {
+    SDL_CloseAudioDevice(sdl_device_id_);
+    sdl_device_id_ = -1;
+  }
+  if (sdl_initialized_) {
+    SDL_QuitSubSystem(SDL_INIT_AUDIO);
+    sdl_initialized_ = false;
+  }
+  std::unique_lock<std::mutex> guard(frames_mutex_);
+  while (!frames_unused_.empty()) {
+    delete[] frames_unused_.top();
+    frames_unused_.pop();
+  };
+  while (!frames_queued_.empty()) {
+    delete[] frames_queued_.front();
+    frames_queued_.pop();
+  };
+}
+
+}  // namespace sdl
+}  // namespace apu
+}  // namespace xe