AudioStream management functions.

examples/audio_stream_effects/main.lua

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+-- Based on raylib audio_stream_effects example
+
+package.path = package.path..";"..RL.GetBasePath().."../resources/lib/?.lua"
+package.cpath = package.cpath..";"..RL.GetBasePath().."../resources/clib/?.so"
+
+Vector2 = require( "vector2" )
+Rect = require( "rectangle" )
+
+-- NOTE! You have to compile the C lib containing the effects in resources/clib/audioProcess.c
+-- Implementing audio processors in Lua would probably be too slow.
+AudioProcess = require( "audioProcess" )
+
+local music = nil
+local rect = Rect:new()
+local rect2 = Rect:new()
+local effectLPF = nil
+local effectDelay = nil
+local enableEffectLPF = false
+local enableEffectDelay = false
+
+function RL.init()
+	RL.SetWindowTitle( "Audio stream effects" )
+	RL.SetWindowState( RL.FLAG_VSYNC_HINT )
+	RL.InitAudioDevice()
+
+	music = RL.LoadMusicStream( RL.GetBasePath().."../resources/music/Juhani Junkala [Retro Game Music Pack] Title Screen.ogg" )
+
+	RL.PlayMusicStream( music )
+
+	AudioProcess.init()
+	effectLPF = AudioProcess.AudioProcessEffectLPF()
+	effectDelay = AudioProcess.AudioProcessEffectDelay()
+
+	local winSize = Vector2:newT( RL.GetScreenSize() )
+	local barWidth = 256
+
+	rect:set(
+		winSize.x / 2 - barWidth / 2,
+		winSize.y / 2 - 5,
+		barWidth,
+		10
+	)
+	rect2:setR( rect )
+end
+
+function RL.update( delta )
+	RL.UpdateMusicStream( music )
+
+	-- Add/Remove effect: lowpass filter
+	if RL.IsKeyPressed( RL.KEY_F ) then
+		local stream = RL.GetMusicStream( music )
+		enableEffectLPF = not enableEffectLPF
+
+		if enableEffectLPF then
+			RL.AttachAudioStreamProcessor( stream, effectLPF )
+			-- RL.AttachAudioMixedProcessor( effectLPF )
+		else
+			RL.DetachAudioStreamProcessor( stream, effectLPF )
+			-- RL.DetachAudioMixedProcessor( effectLPF )
+		end
+	end
+
+	-- Add/Remove effect: delay
+	if RL.IsKeyPressed( RL.KEY_D ) then
+		local stream = RL.GetMusicStream( music )
+		enableEffectDelay = not enableEffectDelay
+
+		if enableEffectDelay then
+			RL.AttachAudioStreamProcessor( stream, effectDelay )
+			-- RL.AttachAudioMixedProcessor( effectDelay )
+		else
+			RL.DetachAudioStreamProcessor( stream, effectDelay )
+			-- RL.DetachAudioMixedProcessor( effectDelay )
+		end
+	end
+end
+
+function RL.draw()
+	local musicLen = RL.GetMusicTimeLength( music )
+	local musicPos = RL.GetMusicTimePlayed( music )
+
+	RL.ClearBackground( RL.RAYWHITE )
+
+	RL.DrawText(
+		"PRESS F TO TOGGLE LPF EFFECT "..( enableEffectLPF and "ON" or "OFF" ),
+		Vector2:temp( rect.x - 80, rect.y - 80 ), 20, RL.GRAY
+	)
+	RL.DrawText(
+		"PRESS D TO TOGGLE DELAY EFFECT "..( enableEffectDelay and "ON" or "OFF" ),
+		Vector2:temp( rect.x - 90, rect.y - 40 ), 20, RL.GRAY
+	)
+
+	RL.DrawRectangleLines( rect + Rect:temp( 0, -1, 1, 1 ), RL.BLACK )
+	rect2.width = musicPos / musicLen * rect.width
+	RL.DrawRectangle( rect2, RL.RED )
+end
+
+function RL.exit()
+	AudioProcess.free()
+end

examples/resources/clib/.gitignore

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+*.so

examples/resources/clib/audioProcess.c

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+/* Based on raylib audio_stream_effects example */
+
+#include <lua.h>
+#include <lauxlib.h>
+#include <lualib.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* gcc audioProcess.c -shared -o audioProcess.so -fPIC -llua */
+
+// Audio effect: lowpass filter
+void AudioProcessEffectLPF(void *buffer, unsigned int frames)
+{
+	static float low[2] = { 0.0f, 0.0f };
+	static const float cutoff = 70.0f / 44100.0f; // 70 Hz lowpass filter
+	const float k = cutoff / (cutoff + 0.1591549431f); // RC filter formula
+
+	// Converts the buffer data before using it
+	float *bufferData = (float *)buffer;
+	for (unsigned int i = 0; i < frames*2; i += 2)
+	{
+		const float l = bufferData[i];
+		const float r = bufferData[i + 1];
+
+		low[0] += k * (l - low[0]);
+		low[1] += k * (r - low[1]);
+		bufferData[i] = low[0];
+		bufferData[i + 1] = low[1];
+	}
+}
+
+static float *delayBuffer = NULL;
+static unsigned int delayBufferSize = 0;
+static unsigned int delayReadIndex = 2;
+static unsigned int delayWriteIndex = 0;
+
+// Audio effect: delay
+static void AudioProcessEffectDelay(void *buffer, unsigned int frames)
+{
+	for (unsigned int i = 0; i < frames*2; i += 2)
+	{
+		float leftDelay = delayBuffer[delayReadIndex++];    // ERROR: Reading buffer -> WHY??? Maybe thread related???
+		float rightDelay = delayBuffer[delayReadIndex++];
+
+		if (delayReadIndex == delayBufferSize) delayReadIndex = 0;
+
+		((float *)buffer)[i] = 0.5f*((float *)buffer)[i] + 0.5f*leftDelay;
+		((float *)buffer)[i + 1] = 0.5f*((float *)buffer)[i + 1] + 0.5f*rightDelay;
+
+		delayBuffer[delayWriteIndex++] = ((float *)buffer)[i];
+		delayBuffer[delayWriteIndex++] = ((float *)buffer)[i + 1];
+		if (delayWriteIndex == delayBufferSize) delayWriteIndex = 0;
+	}
+}
+
+/* API. */
+
+static int apInit( lua_State* L ) {
+	// Allocate buffer for the delay effect
+    delayBufferSize = 48000*2;      // 1 second delay (device sampleRate*channels)
+    delayBuffer = (float *)calloc(delayBufferSize, sizeof(float));
+
+	return 0;
+}
+
+static int getAudioProcessEffectLPF( lua_State* L ) {
+	lua_pushlightuserdata( L, AudioProcessEffectLPF );
+
+	return 1;
+}
+
+static int getAudioProcessEffectDelay( lua_State* L ) {
+	lua_pushlightuserdata( L, AudioProcessEffectDelay );
+
+	return 1;
+}
+
+static int apFree( lua_State* L ) {
+	free(delayBuffer);       // Free delay buffer
+
+	return 0;
+}
+
+static const luaL_Reg audioProcess[] = {
+	{ "init", apInit },
+	{ "AudioProcessEffectLPF", getAudioProcessEffectLPF },
+	{ "AudioProcessEffectDelay", getAudioProcessEffectDelay },
+	{ "free", apFree },
+	{ NULL, NULL } // sentinel.
+};
+
+int luaopen_audioProcess(lua_State *L) {
+#if LUA_VERSION_NUM <= 501
+	luaL_openlib( L, "audioProcess", audioProcess, 0 );
+#else
+	luaL_newlib( L, audioProcess );
+#endif
+	return 1;
+}

examples/resources/music/LICENCE

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+Resource												Author						Licence					Source														Edits
+Juhani Junkala [Retro Game Music Pack] Title Screen		Juhani Junkala			 	CC0						https://opengameart.org/content/5-chiptunes-action