From 83aafa31f047a4937dec971a9e2d1ee8727e28a1 Mon Sep 17 00:00:00 2001
From: wheremyfoodat <44909372+wheremyfoodat@users.noreply.github.com>
Date: Fri, 22 Nov 2024 02:33:57 +0200
Subject: [PATCH] Better audio playback code

---
 include/audio/dsp_core.hpp          |  3 ++-
 include/audio/miniaudio_device.hpp  |  5 +++-
 src/core/audio/miniaudio_device.cpp | 36 +++++++++++++++++++++--------
 3 files changed, 32 insertions(+), 12 deletions(-)

diff --git a/include/audio/dsp_core.hpp b/include/audio/dsp_core.hpp
index 5addfd19..5a434b91 100644
--- a/include/audio/dsp_core.hpp
+++ b/include/audio/dsp_core.hpp
@@ -24,7 +24,8 @@ namespace Audio {
 	static constexpr u64 lleSlice = 16384;
 
 	class DSPCore {
-		using Samples = Common::RingBuffer<s16, 1024>;
+		// 0x2000 stereo (= 2 channel) samples
+		using Samples = Common::RingBuffer<s16, 0x2000 * 2>;
 
 	  protected:
 		Memory& mem;
diff --git a/include/audio/miniaudio_device.hpp b/include/audio/miniaudio_device.hpp
index 3a658e58..f3b212e2 100644
--- a/include/audio/miniaudio_device.hpp
+++ b/include/audio/miniaudio_device.hpp
@@ -3,11 +3,12 @@
 #include <string>
 #include <vector>
 
+#include "helpers.hpp"
 #include "miniaudio.h"
 #include "ring_buffer.hpp"
 
 class MiniAudioDevice {
-	using Samples = Common::RingBuffer<ma_int16, 1024>;
+	using Samples = Common::RingBuffer<ma_int16, 0x2000 * 2>;
 	static constexpr ma_uint32 sampleRate = 32768;  // 3DS sample rate
 	static constexpr ma_uint32 channelCount = 2;    // Audio output is stereo
 
@@ -20,6 +21,8 @@ class MiniAudioDevice {
 	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:
diff --git a/src/core/audio/miniaudio_device.cpp b/src/core/audio/miniaudio_device.cpp
index 265f2f78..cd537aef 100644
--- a/src/core/audio/miniaudio_device.cpp
+++ b/src/core/audio/miniaudio_device.cpp
@@ -1,5 +1,7 @@
 #include "audio/miniaudio_device.hpp"
 
+#include <cstring>
+
 #include "helpers.hpp"
 
 MiniAudioDevice::MiniAudioDevice() : initialized(false), running(false), samples(nullptr) {}
@@ -87,20 +89,34 @@ void MiniAudioDevice::init(Samples& samples, bool safe) {
 	deviceConfig.aaudio.usage = ma_aaudio_usage_game;
 	deviceConfig.wasapi.noAutoConvertSRC = true;
 
+	lastStereoSample = {0, 0};
+
 	deviceConfig.dataCallback = [](ma_device* device, void* out, const void* input, ma_uint32 frameCount) {
 		auto self = reinterpret_cast<MiniAudioDevice*>(device->pUserData);
-		s16* output = reinterpret_cast<ma_int16*>(out);
-		const usize maxSamples = std::min(self->samples->Capacity(), usize(frameCount * channelCount));
-
-		// Wait until there's enough samples to pop
-		while (self->samples->size() < maxSamples) {
-			// If audio output is disabled from the emulator thread, make sure that this callback will return and not hang
-			if (!self->running) {
-				return;
-			}
+		if (!self->running) {
+			return;
 		}
 
-		self->samples->pop(output, maxSamples);
+		s16* output = reinterpret_cast<ma_int16*>(out);
+		usize samplesWritten = 0;
+		samplesWritten += self->samples->pop(output, frameCount * channelCount);
+
+		// Get the last sample for underrun handling
+		if (samplesWritten != 0) {
+			std::memcpy(&self->lastStereoSample[0], &output[(samplesWritten - 1) * 2], sizeof(lastStereoSample));
+		}
+
+		// If underruning, copy the last output sample
+		{
+			s16* pointer = &output[samplesWritten * 2];
+			s16 l = self->lastStereoSample[0];
+			s16 r = self->lastStereoSample[1];
+
+			for (usize i = samplesWritten; i < frameCount; i++) {
+				*pointer++ = l;
+				*pointer++ = r;
+			}
+		}
 	};
 
 	if (ma_device_init(&context, &deviceConfig, &device) != MA_SUCCESS) {