Licar/audio.h

/**
  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_SMALL 2
#define LCR_SOUND_CRASH_BIG 3
#define LCR_SOUND_ACCELERATOR 4

#define LCR_AUDIO_CRASH_LEN 2048


struct
{
  uint32_t frame;
  uint8_t soundPlayed;
  uint16_t soundPlayedSample;
  uint32_t noise;


int engineIntensity;
int engineOsc;
int engineInc;

} 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.engineInc = 1;

LCR_audio.engineIntensity = 0;


}

void LCR_audioSetEngineIntensity(uint8_t value)
{
  LCR_audio.engineIntensity = value;
}

void LCR_audioPlaySound(uint8_t sound)
{
  LCR_LOG2("playing 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;

switch (LCR_audio.soundPlayed)
{
  case LCR_SOUND_CRASH_SMALL: 
    result += (LCR_AUDIO_CRASH_LEN - LCR_audio.soundPlayedSample) *
      (_LCR_audioNoise() / 16) / LCR_AUDIO_CRASH_LEN;

    if (LCR_audio.soundPlayedSample >= LCR_AUDIO_CRASH_LEN)
      LCR_audio.soundPlayed = LCR_SOUND_NONE;

    break;

  case LCR_SOUND_CRASH_BIG:
    result += ((LCR_AUDIO_CRASH_LEN * 2) - LCR_audio.soundPlayedSample) *
      (_LCR_audioNoise() / 8) / (2 * LCR_AUDIO_CRASH_LEN);

    if (LCR_audio.soundPlayedSample >= 2 * LCR_AUDIO_CRASH_LEN)
      LCR_audio.soundPlayed = LCR_SOUND_NONE;

    break;

  default:
    break;
}

if (LCR_audio.soundPlayed != LCR_SOUND_NONE)
  LCR_audio.soundPlayedSample++;
else
{
  LCR_audio.engineOsc +=
    LCR_audio.engineInc ?
      (((_LCR_audioNoise() % 256) <
      (10 + LCR_audio.engineIntensity))) : -31;

  if (LCR_audio.engineInc && LCR_audio.engineOsc >
    (90 + (LCR_audio.engineIntensity / 8)))
    LCR_audio.engineInc = 0;
  else if ((!LCR_audio.engineInc) && LCR_audio.engineOsc < 10)
    LCR_audio.engineInc = 1;

  result +=
    LCR_audio.engineIntensity < 20 ?
      LCR_audio.engineOsc / 2 : LCR_audio.engineOsc;
}

  LCR_audio.frame++;

  return result;
}



#endif // guard