audio: minimal streaming API

This will allow us to generate sounds on the fly on several dedicated
channels. Until now we could only play fully loaded samples.

.gitignore

@@ -95,6 +95,7 @@ doc/tutorial/05_easymesh
 doc/tutorial/06_sprite
 doc/tutorial/07_input
 doc/tutorial/08_fbo
+doc/tutorial/09_sound
 doc/tutorial/11_fractal
 doc/tutorial/12_voronoi
 doc/tutorial/13_shader_builder

doc/tutorial/09_sound.cpp

@@ -0,0 +1,114 @@
+//
+//  Lol Engine — Sound tutorial
+//
+//  Copyright © 2011—2016 Sam Hocevar <sam@hocevar.net>
+//
+//  Lol Engine is free software. It comes without any warranty, to
+//  the extent permitted by applicable law. You can redistribute it
+//  and/or modify it under the terms of the Do What the Fuck You Want
+//  to Public License, Version 2, as published by the WTFPL Task Force.
+//  See http://www.wtfpl.net/ for more details.
+//
+
+#if HAVE_CONFIG_H
+#   include "config.h"
+#endif
+
+#include <lol/engine.h>
+
+#include <functional>
+
+using namespace lol;
+
+class sound_demo : public WorldEntity
+{
+public:
+    sound_demo()
+    {
+        for (auto &val : m_streams)
+            val = -1;
+
+        m_controller = new Controller("Default");
+        m_profile << InputProfile::Keyboard(0, "Space")
+                  << InputProfile::MouseKey(1, "Left");
+        m_controller->Init(m_profile);
+        m_mouse = InputDevice::GetMouse();
+
+        m_text = new Text("SPACE for sine wave, Left Click for white noise",
+                          "data/font/ascii.png");
+        m_text->SetPos(vec3(5, 5, 1));
+        Ticker::Ref(m_text);
+    }
+
+    ~sound_demo()
+    {
+        Ticker::Unref(m_text);
+    }
+
+    void synth(int mode, void *buf, int bytes)
+    {
+        uint16_t *stream = (uint16_t *)buf;
+        for (int i = 0; i < bytes / 2; ++i)
+        {
+            switch (mode)
+            {
+            case 0: // sine wave
+                stream[i] = 400 * lol::sin(12 * i * F_TAU / bytes);
+                break;
+            case 1: // white noise
+                stream[i] = lol::rand(-120, 120);
+                break;
+            }
+        }
+    }
+
+    virtual void TickGame(float seconds)
+    {
+        WorldEntity::TickGame(seconds);
+
+        for (int i = 0; i < 2; ++i)
+        {
+            if (!m_controller->WasKeyPressedThisFrame(i))
+                continue;
+
+            if (m_streams[i] < 0)
+            {
+                auto f = std::bind(&sound_demo::synth, this, i,
+                                   std::placeholders::_1,
+                                   std::placeholders::_2);
+                m_streams[i] = audio::start_streaming(f);
+            }
+            else
+            {
+                audio::stop_streaming(m_streams[i]);
+                m_streams[i] = -1;
+            }
+        }
+    }
+
+    virtual void TickDraw(float seconds, Scene &scene)
+    {
+        WorldEntity::TickDraw(seconds, scene);
+    }
+
+private:
+    int m_streams[2];
+
+    InputDevice *m_mouse;
+    Controller *m_controller;
+    InputProfile m_profile;
+
+    Text *m_text;
+};
+
+int main(int argc, char **argv)
+{
+    sys::init(argc, argv);
+
+    Application app("Tutorial 9: Sound", ivec2(640, 480), 60.0f);
+    new sound_demo();
+    app.Run();
+
+    return EXIT_SUCCESS;
+}
+

doc/tutorial/Makefile.am

@@ -3,7 +3,7 @@ include $(top_srcdir)/build/autotools/common.am
 
 if BUILD_TUTORIAL
 noinst_PROGRAMS = 01_triangle 02_cube 03_noise 04_texture 05_easymesh \
-                  06_sprite 07_input 08_fbo 11_fractal \
+                  06_sprite 07_input 08_fbo 09_sound 11_fractal \
                   12_voronoi 13_shader_builder 14_lol_lua
 endif
 
@@ -43,6 +43,10 @@ endif
 08_fbo_CPPFLAGS = $(AM_CPPFLAGS)
 08_fbo_DEPENDENCIES = @LOL_DEPS@
 
+09_sound_SOURCES = 09_sound.cpp
+09_sound_CPPFLAGS = $(AM_CPPFLAGS)
+09_sound_DEPENDENCIES = @LOL_DEPS@
+
 11_fractal_SOURCES = 11_fractal.cpp 11_fractal.lolfx
 11_fractal_CPPFLAGS = $(AM_CPPFLAGS)
 11_fractal_DEPENDENCIES = @LOL_DEPS@

src/audio/audio.cpp

@@ -28,14 +28,26 @@
 namespace lol
 {
 
-/*
+struct audio_streamer
+{
+    int m_channel;
+    std::function<void(void *, int)> m_callback;
+#if defined LOL_USE_SDL_MIXER
+    Mix_Chunk *m_chunk;
+#endif
+};
+
+array<audio_streamer *> g_streamers;
+
+ /*
  * Public audio class
  */
 
 void audio::init()
 {
 #if defined LOL_USE_SDL_MIXER
-    Mix_OpenAudio(22050, AUDIO_S16, 8, 1024);
+    Mix_OpenAudio(22050, AUDIO_S16, 2, 1024);
+    set_channels(8);
 #endif
 }
 
@@ -61,8 +73,6 @@ void audio::mute_all()
 {
 #if defined LOL_USE_SDL_MIXER
     Mix_Volume(-1,0);
-#else
-    UNUSED(false);
 #endif
 }
 
@@ -70,8 +80,50 @@ void audio::unmute_all()
 {
 #if defined LOL_USE_SDL_MIXER
     Mix_Volume(-1,MIX_MAX_VOLUME);
+#endif
+}
+
+int audio::start_streaming(std::function<void(void *, int)> const &f)
+{
+#if defined LOL_USE_SDL_MIXER
+    static auto trampoline = [](int, void *stream, int bytes, void *udata)
+    {
+        auto s = (audio_streamer *)udata;
+        s->m_callback(stream, bytes);
+    };
+
+    audio_streamer *s = new audio_streamer();
+    g_streamers.push(s);
+
+    array<uint8_t> empty;
+    empty.resize(1024);
+    s->m_chunk = Mix_QuickLoad_RAW(empty.data(), empty.bytes());
+    s->m_channel = Mix_PlayChannel(-1, s->m_chunk, -1);
+    s->m_callback = f;
+    Mix_RegisterEffect(s->m_channel, trampoline, nullptr, s);
+
+    return s->m_channel;
+#else
+    UNUSED(f);
+    return -1;
+#endif
+}
+
+void audio::stop_streaming(int channel)
+{
+#if defined LOL_USE_SDL_MIXER
+    for (int i = 0; i < g_streamers.count(); ++i)
+    {
+        if (g_streamers[i]->m_channel == channel)
+        {
+            Mix_HaltChannel(channel);
+            delete g_streamers[i];
+            g_streamers.remove(i);
+            return;
+        }
+    }
 #else
-    UNUSED(false);
+    UNUSED(channel);
 #endif
 }
 

src/lol/audio/audio.h

@@ -18,7 +18,7 @@
 // Helper functions to set up the audio device.
 //
 
-#include <stdint.h>
+#include <functional>
 
 namespace lol
 {
@@ -33,6 +33,9 @@ public:
     static void mute_all();
     static void unmute_all();
 
+    static int start_streaming(std::function<void(void *, int)> const &f);
+    static void stop_streaming(int channel);
+
 private:
     audio() {}
 };