_sfx.hpp 2023-12-08

#pragma once

#include <sfx.hpp>


//500ms
#define _totalFadeDelay (0.500f)

//linearly fade over the course of 10ms
#define _fadeDeltaSeconds (0.010f)

//the most common audio clipping ends at 10-11ms after unpausing,
 //but i've seen clipping as far as ~450ms after unpausing
#define _fadeInDelaySeconds (_totalFadeDelay - _fadeDeltaSeconds)


//lower clip's volume to 0 within 10ms if speed reaches 0
#define _speed0DeltaVolMS (10.0f)




#ifndef LERP2
#define LERP2(_v0,_v1, _t) ( (_v0) + (_t)*((_v1)-(_v0)) )
#endif

static inline sfx_f32s sfx_linearSample(std::vector<sfx_f32s>& src,
                                        double& position)
{
  Uint64 intPosition = (Uint64)position;
  double modPosition = position-intPosition;

  sfx_f32s smpA = src.at(  intPosition);
  sfx_f32s smpB = src.at(++intPosition);

  sfx_f32s smpOut(
    LERP2(smpA.l, smpB.l, modPosition),
    LERP2(smpA.r, smpB.r, modPosition)
  );
  return smpOut;
}




/****************/
/* sfx_callback */
/****************/

static inline sfx_f32s& _sfx_applyPan(sfx_f32s& sample, float pan){
  //(i think this is how audacity does it...)
  if(pan < 0){
    sample.l += sample.r*(-pan);
    sample.r *= 1.0f+pan;
  } else if(pan > 0){
    sample.r += sample.l*pan;
    sample.l *= 1.0f-pan;
  }
  return sample;
}


static inline void _sfx_mixTrack(sfx_track& track, Uint64 sfxTimeStampEnd,
                                 sfx_f32s* dst, int dst_len)
{
  sfx_pcm* pcm = track.pcm;
  const sfx_f32s speed0VolumeDelta = -( (1000.0f/_speed0DeltaVolMS) / pcm->sampleRate );

  if(track.timeStamp > 0){


    //calculate position based on difference between device and clip timestamps
     //(timeStampEnd is used instead of Start, so the clip's time stamp
     // can be compared to the last time the device callback exited)
    double difference = (double)(track.timeStamp-sfxTimeStampEnd)/1000;
    difference *= pcm->sampleRate; //convert seconds to samples
    track.position = -(difference*track.speed); //starts playing when position reaches 0

    track.timeStamp = 0; //to ensure that this only occurs once per clip queued
  }


  //make copies of relevant track values
  float  pan       = std::clamp(track.pan, -1.0f,1.0f);
  Uint64 loopStart = pcm->loopStart;
  Uint64 loopEnd   = pcm->loopEnd-1; //might remove the -1 if needed
  std::vector<sfx_f32s>& src = *pcm->samples;
   //
  double position = track.position;
  double speed    = track.speed;
  Uint16 loops    = track.loops;
  bool   stopping = track.stopping;

  //make sure volume is clamped before applying it to the first sample,
   //since volume is only clamped after volumeDelta is applied otherwise
  track.volume.unit(); //clamp to 0.0 -> 1.0


  for(int i=0; i<dst_len; ++i){
    //loop handling (or end-of-clip handling i guess)
    if(stopping){ dst[i] = 0.0f; continue; } //write silence if clip is stopping
    if(position >= loopEnd){ //clip finished loop
      if(!loops){ stopping = true; dst[i] = 0.0f; continue; } //mark as inactive
      if(loops != 0xffff) --loops; //decrement loops (unless infinite)
      position -= (Uint64)position; //basically position %= 1
      position += loopStart; //now new_position = loopStart + old_position%1

    } else if(position < 0){ //clip has yet to start playing
      if(position < -speed){
        position += speed; //step forward by current speed
        dst[i] = 0.0f; continue; //0 for silent sample
      } else { //if position >= -speed, the clip should start next sample
        position = 0; //make sure clip starts at 0
      }

    }

    //get sample, apply volume, hard clip
    sfx_f32s sample = sfx_linearSample(src,position);
    sample *= track.volume;
    sample.clip();

    //apply pan, apply volumeDelta, clamp volume to 0.0f -> 1.0f
    dst[i] += _sfx_applyPan(sample,pan);
    track.volume += track.volumeDelta;
    track.volume.unit();

    //update position, apply speedDelta, start fade out if clip's speed <= 0
    position += speed;
    speed += track.speedDelta;
    if(speed <= 0){
      speed = 0;
      track.volumeDelta = speed0VolumeDelta;
    }
  }


  //update relevant values in track
  track.position = position;
  track.speed    = speed;
  track.loops    = loops;
  track.stopping = stopping;

  if(track.volume.l<=0 && track.volume.r<=0  &&  track.stopOnMute)
    track.stopping = true;

  if(track.stopping) track.pcm = nullptr;
}



extern int _sfx_pauseThread(void* data);

static inline void _sfx_globalFade(sfx_class* sfx, sfx_f32s* stream, int len){
  sfx_f32s fadeDelta      = sfx->_getFadeDelta();
  sfx_f32s fadeVolume     = sfx->_getFadeVolume();
  Uint32&  fadeInDelayRef = sfx->_getFadeInDelay();
  Uint32   fadeInDelay    = fadeInDelayRef;

  int i = 0; //this index is shared, as the loops can jump to others at will


  //FADING OUT
  if(sfx->isFadingOut()){ _fade_out_:;
    for(; i<len; ++i){
      if(!sfx->isFadingOut()) goto _fade_in_;
      stream[i] *= fadeVolume;
      fadeVolume -= fadeDelta;
      if(fadeVolume.l < 0) fadeVolume = 0.0f;
    }

    //trigger pause thread if fade out is complete
    if(fadeVolume.l <= 0.0f){
      SDL_Thread* pauseThread = SDL_CreateThread(_sfx_pauseThread,"_PauseTh", sfx);
      //setting _fadeInDelay to -1 will cause further calls to the device callback
       //to simply memset 0 until sfx_class::pause() is called again
      if(pauseThread == NULL) fadeInDelayRef = 0xffffffff;
      else SDL_DetachThread(pauseThread); //make sure thread cleans up when finished
    }


  //FADING IN
  } else if(fadeVolume.l < 1.0f){
    //let device warm up before fading in
    for(; (fadeInDelay)&&(i<len); ++i){
      stream[i] = 0.0f;  --fadeInDelay;
    }

    _fade_in_:;
    for(; i<len; ++i){
      if(sfx->isFadingOut()) goto _fade_out_;
      else if(fadeVolume.l >= 1.0f){ fadeVolume = 1.0f; break; }
      stream[i] *= fadeVolume;
      fadeVolume += fadeDelta;
    }

  }


  //even if no fade is being done, output should be hard clipped no matter what
  for(i=0; i<len; ++i) stream[i].clip();


  //update any relevant new values for sfx
  sfx->_getFadeVolume() = fadeVolume.l; //.l should equal .r anyway
  if(fadeInDelayRef != 0xffffffff) fadeInDelayRef = fadeInDelay;
}