Start engine sound

audio.h

@@ -0,0 +1,82 @@
+/**
+  audio: this file implements the audio system.
+*/
+
+#ifndef _LCR_AUDIO
+#define _LCR_AUDIO
+
+#define LCR_SOUND_NONE 0
+#define LCR_SOUND_CLICK 1
+#define LCR_SOUND_CRASH 2
+#define LCR_SOUND_ACCELERATOR 3
+
+#define LCR_AUDIO_MIN_RPM 128
+#define LCR_AUDIO_MAX_RPM 2048
+
+struct
+{
+  uint32_t frame;
+  uint8_t soundPlayed;
+  uint16_t soundPlayedSample;
+  uint32_t noise;
+
+
+int engineIntensity;
+int engineOsc;
+
+
+
+
+} LCR_audio;
+
+void LCR_audioInit(void)
+{
+  LCR_LOG0("initializing audio");
+  LCR_audio.frame = 0;
+  LCR_audio.soundPlayed = LCR_SOUND_NONE;
+  LCR_audio.soundPlayedSample = 0;
+  LCR_audio.noise = 0;
+
+LCR_audio.engineOsc = 0;
+LCR_audio.engineIntensity = 0;
+
+}
+
+void LCR_audioSetEngineIntensity(uint8_t value)
+{
+  LCR_audio.engineIntensity = value;
+}
+
+void LCR_audioPlaySound(uint8_t sound)
+{
+  LCR_audio.soundPlayed = sound;
+  LCR_audio.soundPlayedSample = 0;
+}
+
+uint8_t _LCR_audioNoise(void)
+{
+  LCR_audio.noise = LCR_audio.noise * 32310901 + 37;
+  return LCR_audio.noise >> 16;
+}
+
+uint8_t LCR_audioGetNextSample(void)
+{
+  unsigned char result = 128;
+
+  if (LCR_audio.engineIntensity > 5)
+  {
+    LCR_audio.engineOsc += 
+      ((_LCR_audioNoise() % 256) < 
+        (30 + LCR_audio.engineIntensity));
+
+    result += LCR_audio.engineOsc;
+  }
+
+  LCR_audio.frame++;
+
+  return result;
+}
+
+
+
+#endif // guard

frontend_sdl.c

@@ -26,7 +26,11 @@ void audioFillCallback(void *userdata, uint8_t *s, int l)
         rewind(musicFile);
     }
 
-    s[i] = byte;
+//    s[i] = byte;
+
+s[i] = byte / 2 + LCR_gameGetNextAudioSample() / 2;
+
+
   }
 }
 

game.h

@@ -42,6 +42,11 @@
   - Implement the below described functions according to their description.
   - Implement the main program and game loop.
   - Call the below described functions as described.
+  - If you want to support music, make your frontend play music from the "music"
+    file in assets. It is in raw format, storing 8bit unsigned samples at 8000
+    Hz. Use the LCR_gameGetMusicVolume to check what the music volume is. If you
+    don't support music, set LCR_SETTING_MUSIC to 0 in your frontend code so
+    that the game knows music is disabled.
 */
 
 /**
@@ -93,6 +98,16 @@ void LCR_gameEnd(void);
 */
 uint8_t LCR_gameStep(uint32_t timeMs);
 
+/**
+  Gets the current music volume;
+*/
+uint8_t LCR_gameGetMusicVolume(void);
+
+/**
+  Gets next audio sample (unsigned 8bit samples, 8 KHz).
+*/
+uint8_t LCR_gameGetNextAudioSample(void);
+
 //------------------------------------------------------------------------------
 
 #define LCR_LOG0(s) ;
@@ -133,8 +148,19 @@ struct
   uint8_t debugDraw;
   uint8_t checkpointsTaken;
   uint32_t runTime;
+
+  uint8_t musicVolume;
 } LCR_game;
 
+uint8_t LCR_gameGetMusicVolume(void)
+{
+#if LCR_SETTING_MUSIC
+  return LCR_game.musicVolume;
+#else
+  return 0;
+#endif
+}
+
 void LCR_drawPixelXYUnsafe(unsigned int x, unsigned int y,
   uint16_t color);
 
@@ -149,6 +175,7 @@ static inline void LCR_drawPixelXYSafe(unsigned int x, unsigned int y,
 #include "racing.h"
 #include "assets.h"
 #include "renderer.h"
+#include "audio.h"
 
 uint8_t LCR_keyStates[LCR_KEYS_TOTAL]; /**< Assures unchanging key states
                                             during a single frame, holds
@@ -219,12 +246,12 @@ void LCR_gameInit(void)
 
   LCR_rendererInit();
   LCR_racingInit();
+  LCR_audioInit();
 
+  LCR_game.musicVolume = 255;
   LCR_game.nextRenderFrameTime = 0;
   LCR_game.nextRacingTickTime = 0;
-
   LCR_game.controlMode = LCR_CONTROL_MODE_FREECAM;
-
   LCR_gameStartRun(LCR_maps[0]);
 }
 
@@ -369,6 +396,8 @@ LCR_GameUnit physicsInterpolationParam = LCR_GAME_UNIT -
 
     int val = LCR_carSpeedKMH();
 
+LCR_audioSetEngineIntensity(val < 256 ? val : 255);
+
     if (val < 5) // don't show tiny oscillations when still
       val = 0;
 
@@ -424,4 +453,9 @@ LCR_GameUnit physicsInterpolationParam = LCR_GAME_UNIT -
   return 1;
 }
 
+uint8_t LCR_gameGetNextAudioSample(void)
+{
+  return LCR_audioGetNextSample();
+}
+
 #endif // guard

settings.h

@@ -172,4 +172,9 @@
   #define LCR_SETTING_POTATO_GRAPHICS 0
 #endif
 
+#ifndef LCR_SETTING_MUSIC
+  /** Whether to enable in game music. */
+  #define LCR_SETTING_MUSIC 1
+#endif
+
 #endif // guard