[WIP] Libretro: Add audio support (#714)

* Libretro: Add audio support

* Adding audio interface part 1

* Audio device pt 2

* More audio device

* More audio device

* Morea uudi odevice

* More audio device

* More audio device

* More audio device

---------

Co-authored-by: wheremyfoodat <44909372+wheremyfoodat@users.noreply.github.com>

CMakeLists.txt

@@ -402,7 +402,8 @@ set(HEADER_FILES include/emulator.hpp include/helpers.hpp include/termcolor.hpp
                  include/align.hpp include/audio/aac_decoder.hpp include/PICA/pica_simd.hpp include/services/fonts.hpp
                  include/audio/audio_interpolation.hpp include/audio/hle_mixer.hpp include/audio/dsp_simd.hpp
                  include/services/dsp_firmware_db.hpp include/frontend_settings.hpp include/fs/archive_twl_photo.hpp
-                 include/fs/archive_twl_sound.hpp include/fs/archive_card_spi.hpp include/services/ns.hpp
+                 include/fs/archive_twl_sound.hpp include/fs/archive_card_spi.hpp include/services/ns.hpp include/audio/audio_device.hpp
+                 include/audio/audio_device_interface.hpp include/audio/libretro_audio_device.hpp
 )
 
 cmrc_add_resource_library(

include/audio/audio_device.hpp

@@ -0,0 +1,9 @@
+#pragma once
+
+#ifdef __LIBRETRO__
+#include "audio/libretro_audio_device.hpp"
+using AudioDevice = LibretroAudioDevice;
+#else
+#include "audio/miniaudio_device.hpp"
+using AudioDevice = MiniAudioDevice;
+#endif

include/audio/audio_device_interface.hpp

@@ -0,0 +1,36 @@
+#pragma once
+#include <array>
+
+#include "config.hpp"
+#include "helpers.hpp"
+#include "ring_buffer.hpp"
+
+class AudioDeviceInterface {
+  protected:
+	static constexpr usize maxFrameCount = 0x2000;
+
+	using Samples = Common::RingBuffer<s16, maxFrameCount * 2>;
+	using RenderBatchCallback = usize (*)(const s16*, usize);
+
+	Samples* samples = nullptr;
+
+	const AudioDeviceConfig& audioSettings;
+	// Store the last stereo sample we output. We play this when underruning to avoid pops.
+	std::array<s16, 2> lastStereoSample{};
+
+  public:
+	AudioDeviceInterface(Samples* samples, const AudioDeviceConfig& audioSettings) : samples(samples), audioSettings(audioSettings) {}
+
+	bool running = false;
+	Samples* getSamples() { return samples; }
+
+	// If safe is on, we create a null audio device
+	virtual void init(Samples& samples, bool safe = false) = 0;
+	virtual void close() = 0;
+
+	virtual void start() = 0;
+	virtual void stop() = 0;
+
+	// Only used for audio devices that render multiple audio frames in one go, eg the libretro audio device.
+	virtual void renderBatch(RenderBatchCallback callback) {}
+};

include/audio/libretro_audio_device.hpp

@@ -0,0 +1,60 @@
+#pragma once
+#include <cstring>
+
+#include "audio/audio_device_interface.hpp"
+
+class LibretroAudioDevice : public AudioDeviceInterface {
+	bool initialized = false;
+
+  public:
+	LibretroAudioDevice(const AudioDeviceConfig& audioSettings) : AudioDeviceInterface(nullptr, audioSettings), initialized(false) {
+		running = false;
+	}
+
+	void init(Samples& samples, bool safe = false) override {
+		this->samples = &samples;
+
+		initialized = true;
+		running = false;
+	}
+
+	void close() override {
+		initialized = false;
+		running = false;
+	};
+
+	void start() override { running = true; }
+	void stop() override { running = false; };
+
+	void renderBatch(RenderBatchCallback callback) override {
+		if (running) {
+			static constexpr usize frameCount = 774;
+			static constexpr usize channelCount = 2;
+			static s16 audioBuffer[frameCount * channelCount];
+
+			usize samplesWritten = 0;
+			samplesWritten += samples->pop(audioBuffer, frameCount * channelCount);
+
+			// Get the last sample for underrun handling
+			if (samplesWritten != 0) {
+				std::memcpy(&lastStereoSample[0], &audioBuffer[(samplesWritten - 1) * 2], sizeof(lastStereoSample));
+			}
+
+			// If underruning, copy the last output sample
+			{
+				s16* pointer = &audioBuffer[samplesWritten * 2];
+				s16 l = lastStereoSample[0];
+				s16 r = lastStereoSample[1];
+
+				for (usize i = samplesWritten; i < frameCount; i++) {
+					*pointer++ = l;
+					*pointer++ = r;
+				}
+			}
+
+			callback(audioBuffer, sizeof(audioBuffer) / (channelCount * sizeof(s16)));
+		}
+	}
+
+	bool isInitialized() const { return initialized; }
+};

include/audio/miniaudio_device.hpp

@@ -3,39 +3,31 @@
 #include <string>
 #include <vector>
 
-#include "config.hpp"
-#include "helpers.hpp"
+#include "audio/audio_device_interface.hpp"
 #include "miniaudio.h"
-#include "ring_buffer.hpp"
 
-class MiniAudioDevice {
-	using Samples = Common::RingBuffer<ma_int16, 0x2000 * 2>;
+class MiniAudioDevice : public AudioDeviceInterface {
 	static constexpr ma_uint32 sampleRate = 32768;  // 3DS sample rate
 	static constexpr ma_uint32 channelCount = 2;    // Audio output is stereo
 
+	bool initialized = false;
+
 	ma_device device;
 	ma_context context;
 	ma_device_config deviceConfig;
-	Samples* samples = nullptr;
-
-	const AudioDeviceConfig& audioSettings;
-
-	bool initialized = false;
-	bool running = false;
 
 	// Store the last stereo sample we output. We play this when underruning to avoid pops.
-	std::array<s16, 2> lastStereoSample;
 	std::vector<std::string> audioDevices;
 
   public:
 	MiniAudioDevice(const AudioDeviceConfig& audioSettings);
 
 	// If safe is on, we create a null audio device
-	void init(Samples& samples, bool safe = false);
-	void close();
+	void init(Samples& samples, bool safe = false) override;
+	void close() override;
 
-	void start();
-	void stop();
+	void start() override;
+	void stop() override;
 
 	bool isInitialized() const { return initialized; }
 };

include/emulator.hpp

@@ -7,8 +7,8 @@
 #include <span>
 
 #include "PICA/gpu.hpp"
+#include "audio/audio_device.hpp"
 #include "audio/dsp_core.hpp"
-#include "audio/miniaudio_device.hpp"
 #include "cheats.hpp"
 #include "config.hpp"
 #include "cpu.hpp"
@@ -48,14 +48,14 @@ class Emulator {
 	Scheduler scheduler;
 
 	Crypto::AESEngine aesEngine;
-	MiniAudioDevice audioDevice;
+	AudioDevice audioDevice;
 	Cheats cheats;
 
   public:
 	static constexpr u32 width = 400;
 	static constexpr u32 height = 240 * 2;  // * 2 because 2 screens
 	ROMType romType = ROMType::None;
-	bool running = false;         // Is the emulator running a game?
+	bool running = false;  // Is the emulator running a game?
 
   private:
 #ifdef PANDA3DS_ENABLE_HTTP_SERVER
@@ -126,6 +126,7 @@ class Emulator {
 	LuaManager& getLua() { return lua; }
 	Scheduler& getScheduler() { return scheduler; }
 	Memory& getMemory() { return memory; }
+	AudioDeviceInterface& getAudioDevice() { return audioDevice; }
 
 	RendererType getRendererType() const { return config.rendererType; }
 	Renderer* getRenderer() { return gpu.getRenderer(); }

src/core/audio/miniaudio_device.cpp

@@ -7,8 +7,9 @@
 
 #include "helpers.hpp"
 
-MiniAudioDevice::MiniAudioDevice(const AudioDeviceConfig& audioSettings)
-	: initialized(false), running(false), samples(nullptr), audioSettings(audioSettings) {}
+MiniAudioDevice::MiniAudioDevice(const AudioDeviceConfig& audioSettings) : AudioDeviceInterface(nullptr, audioSettings), initialized(false) {
+	running = false;
+}
 
 void MiniAudioDevice::init(Samples& samples, bool safe) {
 	this->samples = &samples;
@@ -212,4 +213,4 @@ void MiniAudioDevice::close() {
 		ma_device_uninit(&device);
 		ma_context_uninit(&context);
 	}
-}
+}

src/libretro_core.cpp

@@ -389,6 +389,8 @@ void retro_run() {
 	emulator->runFrame();
 
 	videoCallback(RETRO_HW_FRAME_BUFFER_VALID, emulator->width, emulator->height, 0);
+	// Call audio batch callback
+	emulator->getAudioDevice().renderBatch(audioBatchCallback);
 }
 
 void retro_set_controller_port_device(uint port, uint device) {}