furnace/src/engine/platform/sound/pce_psg.cpp

/* Mednafen - Multi-system Emulator
 *
 *  Original skeleton write handler and PSG structure definition:
 *   Copyright (C) 2001 Charles MacDonald
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

// additional modifications by tildearrow for furnace

#include "pce_psg.h"
#include <stdio.h>
#include <math.h>
#include <string.h>
#include <assert.h>

// Frequency cache cutoff optimization threshold (<= FREQC7M_COT)
#define FREQC7M_COT  0x7 //0xA

void PCE_PSG::SetVolume(double new_volume)
{
        for(int vl = 0; vl < 32; vl++)
        {
         double flub = 1.0 * new_volume * 8 / 6;

         if(vl)
          flub /= pow(2, (double)1 / 4 * vl);                  // ~1.5dB reduction per increment of vl 

   if(vl == 0x1F)
    flub = 0;

         for(int samp = 0; samp < 32; samp++)
         {
    int eff_samp;

    if(revision == REVISION_HUC6280)
     eff_samp = samp * 2;
    else
     eff_samp = samp * 2 - 0x1F;

    dbtable[vl][samp] = (int32_t)(flub * eff_samp * 128); // * 256);
    dbtable_volonly[vl] = (int32_t)(flub * 65536);

    // dbtable[vl][samp] = (int32_t)(flub * eff_samp * 128);
    // dbtable_volonly[vl] = (int32_t)(flub * 65536);
   }
  }
}

// Note: Changing the 0x1F(not that there should be) would require changing the channel pseudo-off volume check logic later on.
static const int scale_tab[] = 
{
        0x00, 0x03, 0x05, 0x07, 0x09, 0x0B, 0x0D, 0x0F,
        0x10, 0x13, 0x15, 0x17, 0x19, 0x1B, 0x1D, 0x1F
};

#define CLOCK_LFSR(lfsr) { unsigned int newbit = ((lfsr >> 0) ^ (lfsr >> 1) ^ (lfsr >> 11) ^ (lfsr >> 12) ^ (lfsr >> 17)) & 1; lfsr = (lfsr >> 1) | (newbit << 17); }

inline void PCE_PSG::UpdateOutputSub(const int32_t timestamp, psg_channel *ch, const int32_t samp0, const int32_t samp1)
{
 int32_t delta[2];

 delta[0] = samp0 - ch->blip_prev_samp[0];
 delta[1] = samp1 - ch->blip_prev_samp[1];

 if (delta[0]) blip_add_delta(bb[0],timestamp,delta[0]);
 if (delta[1]) blip_add_delta(bb[1],timestamp,delta[1]);

 ch->oscBuf->putSample(timestamp-ch->lasttsbase,CLAMP(samp0+samp1,-32768,32767));

 ch->blip_prev_samp[0] = samp0;
 ch->blip_prev_samp[1] = samp1;

}

void PCE_PSG::UpdateOutput_Norm(const int32_t timestamp, psg_channel *ch)
{
 int sv = ch->dda;

 UpdateOutputSub(timestamp, ch, dbtable[ch->vl[0]][sv],
         dbtable[ch->vl[1]][sv]);
}

void PCE_PSG::UpdateOutput_Noise(const int32_t timestamp, psg_channel *ch)
{
 int sv = ((ch->lfsr & 1) << 5) - (ch->lfsr & 1); //(ch->lfsr & 0x1) ? 0x1F : 0;

 UpdateOutputSub(timestamp, ch, dbtable[ch->vl[0]][sv],
        dbtable[ch->vl[1]][sv]);
}

void PCE_PSG::UpdateOutput_Off(const int32_t timestamp, psg_channel *ch)
{
 UpdateOutputSub(timestamp, ch, 0, 0);
}

void PCE_PSG::UpdateOutput_Accum_HuC6280A(const int32_t timestamp, psg_channel *ch)
{
 int32_t samp[2];

 // 31(5-bit max) * 32 samples = 992
 // 992 / 2 = 496
 // 
 // 8 + 5 = 13
 // 13 - 12 = 1

 samp[0] = ((int32_t)dbtable_volonly[ch->vl[0]] * ((int32_t)ch->samp_accum - 496)) >> (8 + 5);
 samp[1] = ((int32_t)dbtable_volonly[ch->vl[1]] * ((int32_t)ch->samp_accum - 496)) >> (8 + 5);

 UpdateOutputSub(timestamp, ch, samp[0], samp[1]);
}

void PCE_PSG::UpdateOutput_Accum_HuC6280(const int32_t timestamp, psg_channel *ch)
{
 int32_t samp[2];

 samp[0] = ((int32_t)dbtable_volonly[ch->vl[0]] * (int32_t)ch->samp_accum) >> (8 + 5);
 samp[1] = ((int32_t)dbtable_volonly[ch->vl[1]] * (int32_t)ch->samp_accum) >> (8 + 5);

 UpdateOutputSub(timestamp, ch, samp[0], samp[1]);
}


// This function should always be called after RecalcFreqCache() (it's not called from RecalcFreqCache to avoid redundant code)
void PCE_PSG::RecalcUOFunc(int chnum)
{
 psg_channel *ch = &channel[chnum];

 //printf("UO Update: %d, %02x\n", chnum, ch->control);

 if((revision != REVISION_HUC6280 && !(ch->control & 0xC0)) || (revision == REVISION_HUC6280 && !(ch->control & 0x80)))
  ch->UpdateOutput = &PCE_PSG::UpdateOutput_Off;
 else if(ch->noisectrl & ch->control & 0x80)
  ch->UpdateOutput = &PCE_PSG::UpdateOutput_Noise;
 // If the control for the channel is in waveform play mode, and the (real) playback frequency is too high, and the channel is either not the LFO modulator channel or
 // if the LFO trigger bit(which halts the LFO modulator channel's waveform incrementing when set) is clear
 else if((ch->control & 0xC0) == 0x80 && ch->freq_cache <= FREQC7M_COT && (chnum != 1 || !(lfoctrl & 0x80)) )
  ch->UpdateOutput = UpdateOutput_Accum;
 else
  ch->UpdateOutput = &PCE_PSG::UpdateOutput_Norm;
}


void PCE_PSG::RecalcFreqCache(int chnum)
{
 psg_channel *ch = &channel[chnum];

 if(chnum == 0 && (lfoctrl & 0x03))
 {
  const uint32_t shift = (((lfoctrl & 0x3) - 1) << 1);
  uint8_t la = channel[1].dda;
  uint32_t tmp_freq = (ch->frequency + ((uint32_t)(la - 0x10) << shift)) & 0xFFF;

  ch->freq_cache = (tmp_freq ? tmp_freq : 4096) << 1;
 }
 else
 {
  ch->freq_cache = (ch->frequency ? ch->frequency : 4096) << 1;

  if(chnum == 1 && (lfoctrl & 0x03))
   ch->freq_cache *= lfofreq ? lfofreq : 256;
 }
}

void PCE_PSG::RecalcNoiseFreqCache(int chnum)
{
 psg_channel *ch = &channel[chnum];
 int32_t freq = 0x1F - (ch->noisectrl & 0x1F);

 if(!freq)
  freq = 0x20;
 else
  freq <<= 6;

 freq <<= 1;

 ch->noise_freq_cache = freq;
}

void PCE_PSG::PeekWave(const unsigned int ch, uint32_t Address, uint32_t Length, uint8_t *Buffer)
{
 assert(ch <= 5);

 while(Length--)
 {
  Address &= 0x1F;
  *Buffer = channel[ch].waveform[Address];
  Address++;
  Buffer++;
 }
}

void PCE_PSG::PokeWave(const unsigned int ch, uint32_t Address, uint32_t Length, const uint8_t *Buffer)
{
 assert(ch <= 5);

 while(Length--)
 {
  Address &= 0x1F;
  channel[ch].samp_accum -= channel[ch].waveform[Address];
  channel[ch].waveform[Address] = *Buffer & 0x1F;
  channel[ch].samp_accum += channel[ch].waveform[Address];
  Address++;
  Buffer++;
 }
}

uint32_t PCE_PSG::GetRegister(const unsigned int id, char *special, const uint32_t special_len)
{
 uint32_t value = 0xDEADBEEF;
 const int ch = (id >> 8) & 0xF;

 switch(id & 0xF0FF)
 {
  default: break;

  case PSG_GSREG_SELECT:
  value = select;
  break;

  case PSG_GSREG_GBALANCE:
  value = globalbalance;
  break;

  case PSG_GSREG_LFOFREQ:
  value = lfofreq;
  break;

  case PSG_GSREG_LFOCTRL:
  value = lfoctrl;
  break;

  case PSG_GSREG_CH0_FREQ:
  value = channel[ch].frequency;
  break;

  case PSG_GSREG_CH0_CTRL:
  value = channel[ch].control;
  break;

  case PSG_GSREG_CH0_BALANCE:
  value = channel[ch].balance;
  break;

  case PSG_GSREG_CH0_WINDEX:
  value = channel[ch].waveform_index;
  break;

  case PSG_GSREG_CH0_SCACHE:
  value = channel[ch].dda;
  break;

  case PSG_GSREG_CH0_NCTRL:
  value = channel[ch].noisectrl;
  break;

  case PSG_GSREG_CH0_LFSR:
  value = channel[ch].lfsr & 0x3FFFF;
  break;
 }
 return(value);
}


void PCE_PSG::SetRegister(const unsigned int id, const uint32_t value)
{
 const int ch = (id >> 8) & 0xF;

 switch(id & 0xF0FF)
 {
  default: break;

  case PSG_GSREG_SELECT:
  select = value & 0x07;
  break;

  case PSG_GSREG_GBALANCE:
  globalbalance = value & 0xFF;
  break;

  case PSG_GSREG_LFOFREQ:
  lfofreq = value & 0xFF;
  break;

  case PSG_GSREG_LFOCTRL:
  lfoctrl = value & 0x83;
        RecalcFreqCache(0);
        RecalcUOFunc(0);
        RecalcFreqCache(1);
        RecalcUOFunc(1);
  break;

  case PSG_GSREG_CH0_FREQ:
  channel[ch].frequency = value & 0xFFF;
  RecalcFreqCache(ch);
  RecalcUOFunc(ch);
  break;

  case PSG_GSREG_CH0_CTRL:
  channel[ch].control = value & 0xFF;
  RecalcFreqCache(ch);
  RecalcUOFunc(ch);
  break;

  case PSG_GSREG_CH0_BALANCE:
  channel[ch].balance = value & 0xFF;
  break;

  case PSG_GSREG_CH0_WINDEX:
  channel[ch].waveform_index = value & 0x1F;
  break;

  case PSG_GSREG_CH0_SCACHE:
  channel[ch].dda = value & 0x1F;
  break;

  case PSG_GSREG_CH0_NCTRL:
  channel[ch].noisectrl = value & 0xFF;
        RecalcNoiseFreqCache(ch);
        RecalcUOFunc(ch);
  break;

  case PSG_GSREG_CH0_LFSR:
  channel[ch].lfsr = value & 0x3FFFF;
  break;
 }
}


#if 0
void PSG_SetRegister(const unsigned int id, const uint32_t value)
{
 

 if(name == "Select")
  PSG_Write(0x00, V);
 else if(name == "GBalance")
  PSG_Write(0x01, V);
 else if(name == "LFOFreq")
 {
  PSG_Write(0x08, V);
 }
 else if(name == "LFOCtrl")
  PSG_Write(0x09, V);
 else if(!strncmp(name.c_str(), "CH", 2))
 {
  unsigned int psg_sel_save = select;
  int ch = name[2] - '0';
  char moomoo[64];
  strncpy(moomoo, name.c_str() + 3, 63);

  PSG_Write(0x00, ch);

  if(!strcmp(moomoo, "Freq"))
  {
   PSG_Write(0x02, V);
   PSG_Write(0x03, V >> 8);
  }
  else if(!strcmp(moomoo, "Ctrl"))
   PSG_Write(0x04, V);
  else if(!strcmp(moomoo, "Balance"))
   PSG_Write(0x05, V);
  else if(!strcmp(moomoo, "WIndex"))
   psg.channel[ch].waveform_index = V & 0x1F;
  else if(!strcmp(moomoo, "SCache"))
   psg.channel[ch].dda = V & 0x1F;
  else if(!strcmp(moomoo, "NCtrl") && ch < 4)
   psg.channel[ch].noisectrl = V;
  else if(!strcmp(moomoo, "LFSR") && ch < 4)
   psg.channel[ch].lfsr = V & 0x3FFFF;

  PSG_Write(0x00, psg_sel_save);
 }
}
#endif

PCE_PSG::PCE_PSG(int want_revision)
{
  //printf("Test: %u, %u\n", sizeof(psg_channel), (uint8_t*)&channel[0].balance - (uint8_t*)&channel[0].waveform[0]);

  revision = want_revision;
  switch(revision)
  {
   default:
    //abort();
    break;

   case REVISION_HUC6280:
    UpdateOutput_Accum = &PCE_PSG::UpdateOutput_Accum_HuC6280;
    break;

   case REVISION_HUC6280A:
    UpdateOutput_Accum = &PCE_PSG::UpdateOutput_Accum_HuC6280A;
    break;
  }
  bb[0]=NULL;
  bb[1]=NULL;

  lastts = 0;
  lasttsbase = 0;
  for(int ch = 0; ch < 6; ch++)
  {
   channel[ch].blip_prev_samp[0] = 0;
   channel[ch].blip_prev_samp[1] = 0;
   channel[ch].lastts = 0;
   channel[ch].lasttsbase = 0;
  }

  SetVolume(1.0);  // Will build dbtable in the process.
  Power(0);
}

PCE_PSG::~PCE_PSG()
{


}

int32_t PCE_PSG::GetVL(const int chnum, const int lr)
{
     psg_channel *ch = &channel[chnum];

     const int gbal = 0x1F - scale_tab[(globalbalance >> (lr ? 0 : 4)) & 0xF];
     const int bal = 0x1F - scale_tab[(ch->balance >> (lr ? 0 : 4)) & 0xF];
     const int al = 0x1F - (ch->control & 0x1F);
     int vol_reduction;

     vol_reduction = gbal + bal + al;

     if(vol_reduction > 0x1F)
      vol_reduction = 0x1F;

     return(vol_reduction);
}

void PCE_PSG::Write(int32_t timestamp, uint8_t A, uint8_t V)
{  
    A &= 0x0F;

    if(A == 0x00)
    {
     select = (V & 0x07);
     return;
    }

    Update(timestamp);

    psg_channel *ch = &channel[select];

    //if(A == 0x01 || select == 5)
     //printf("Write Ch: %d %04x %02x, %d\n", select, A, V, timestamp);

    switch(A)
    {
  default: break;

        case 0x01: /* Global sound balance */
            globalbalance = V;
      vol_pending = true;
            break;

        case 0x02: /* Channel frequency (LSB) */
      if(select > 5) return; // no more than 6 channels, silly game.

            ch->frequency = (ch->frequency & 0x0F00) | V;
      RecalcFreqCache(select);
      RecalcUOFunc(select);
            break;

        case 0x03: /* Channel frequency (MSB) */
      if(select > 5) return; // no more than 6 channels, silly game.

            ch->frequency = (ch->frequency & 0x00FF) | ((V & 0x0F) << 8);
      RecalcFreqCache(select);
      RecalcUOFunc(select);
            break;

        case 0x04: /* Channel enable, DDA, volume */
      if(select > 5) return; // no more than 6 channels, silly game.

            if((ch->control & 0x40) && !(V & 0x40))
      {
       ch->waveform_index = 0;
             ch->dda = ch->waveform[ch->waveform_index];
       ch->counter = ch->freq_cache;
      }

      if(!(ch->control & 0x80) && (V & 0x80)) 
      {
       if(!(V & 0x40))
       {
        ch->waveform_index = (ch->waveform_index + 1) & 0x1F;
        ch->dda = ch->waveform[ch->waveform_index];
       }
      }

            ch->control = V;
      RecalcFreqCache(select);
      RecalcUOFunc(select);

      vol_pending = true;
            break;

        case 0x05: /* Channel balance */
      if(select > 5) return; // no more than 6 channels, silly game.
            ch->balance = V;

      vol_pending = true;
            break;

        case 0x06: /* Channel waveform data */
            if(select > 5) return; // no more than 6 channels, silly game.
            V &= 0x1F;

            if(!(ch->control & 0x40))
      {
       ch->samp_accum -= ch->waveform[ch->waveform_index];
             ch->waveform[ch->waveform_index] = V;
       ch->samp_accum += ch->waveform[ch->waveform_index];
      }

            if((ch->control & 0xC0) == 0x00)
             ch->waveform_index = ((ch->waveform_index + 1) & 0x1F);

      if(ch->control & 0x80)
      {
       // According to my tests(on SuperGrafx), writing to this channel
       // will update the waveform value cache/latch regardless of DDA mode being enabled.
             ch->dda = V;
      }
            break;

        case 0x07: /* Noise enable and frequency */
      if(select > 5) return; // no more than 6 channels, silly game.
            if(select >= 4)
      {
       ch->noisectrl = V;
       RecalcNoiseFreqCache(select);
       RecalcUOFunc(select);
      }
            break;

        case 0x08: /* LFO frequency */
            lfofreq = V & 0xFF;
      //printf("LFO Freq: %02x\n", V);
            break;

        case 0x09: /* LFO trigger and control */
      //printf("LFO Ctrl: %02x\n", V);
      if(V & 0x80)
      {
       channel[1].waveform_index = 0;
       channel[1].dda = channel[1].waveform[channel[1].waveform_index];
       channel[1].counter = channel[1].freq_cache;
      }
            lfoctrl = V;
      RecalcFreqCache(0);
      RecalcUOFunc(0);
      RecalcFreqCache(1);
      RecalcUOFunc(1);
            break;
    }
}

// Don't use inline, which has always_inline in it, due to gcc's inability to cope with the type of recursion
// used in this function.
void PCE_PSG::RunChannel(int chc, int32_t timestamp, const bool LFO_On)
{
 psg_channel *ch = &channel[chc];
 int32_t running_timestamp = ch->lastts;
 int32_t run_time = timestamp - ch->lastts;

 ch->lastts = timestamp;

 if(!run_time) {
  return;
 }

 (this->*ch->UpdateOutput)(running_timestamp, ch);

 if(chc >= 4)
 {
  int32_t freq = ch->noise_freq_cache;

  ch->noisecount -= run_time;

  if(&PCE_PSG::UpdateOutput_Noise == ch->UpdateOutput)
   while(ch->noisecount <= 0)
   {
    CLOCK_LFSR(ch->lfsr);
    UpdateOutput_Noise(timestamp + ch->noisecount, ch);
    ch->noisecount += freq;
   }
  else
   while(ch->noisecount <= 0)
   {
    CLOCK_LFSR(ch->lfsr);
    ch->noisecount += freq;
   }
 }

 // D7 of control is 0, don't clock the counter at all.
 // D7 of lfocontrol is 1(and chc == 1), don't clock the counter at all(not sure about this)
 // In DDA mode, don't clock the counter.
 // (Noise being enabled isn't handled here since AFAIK it doesn't disable clocking of the waveform portion, its sound just overrides the sound from
 //  the waveform portion when the noise enable bit is set, which is handled in our RecalcUOFunc).
 if(!(ch->control & 0x80) || (chc == 1 && (lfoctrl & 0x80)) || (ch->control & 0x40))
  return;

 ch->counter -= run_time;

 if(!LFO_On && ch->freq_cache <= FREQC7M_COT)
 {
  if(ch->counter <= 0)
  {
   const int32_t inc_count = ((0 - ch->counter) / ch->freq_cache) + 1;

   ch->counter += inc_count * ch->freq_cache;

   ch->waveform_index = (ch->waveform_index + inc_count) & 0x1F;
   ch->dda = ch->waveform[ch->waveform_index];
  }
 }

 while(ch->counter <= 0)
 {
  ch->waveform_index = (ch->waveform_index + 1) & 0x1F;
  ch->dda = ch->waveform[ch->waveform_index];

  (this->*ch->UpdateOutput)(timestamp + ch->counter, ch);

  if(LFO_On)
  {
   RunChannel(1, timestamp + ch->counter, false);
   RecalcFreqCache(0);
   RecalcUOFunc(0);

   ch->counter += (ch->freq_cache <= FREQC7M_COT) ? FREQC7M_COT : ch->freq_cache;  // Not particularly accurate, but faster.
  }
  else
   ch->counter += ch->freq_cache;
 }
}

void PCE_PSG::UpdateSubLFO(int32_t timestamp)
{
 for(int chc = 0; chc < 6; chc++)
  RunChannel(chc, timestamp, chc == 0);
}

void PCE_PSG::UpdateSubNonLFO(int32_t timestamp)
{
 for(int chc = 0; chc < 6; chc++)
  RunChannel(chc, timestamp, false);
}

void PCE_PSG::Update(int32_t timestamp)
{
 int32_t run_time = timestamp - lastts;

 if(vol_pending && !vol_update_counter && !vol_update_which)
 {
  vol_update_counter = 1;
  vol_pending = false;
 }

 bool lfo_on = (bool)(lfoctrl & 0x03);

 if(lfo_on)
 {
  if(!(channel[1].control & 0x80) || (lfoctrl & 0x80))
  {
   lfo_on = 0;
   RecalcFreqCache(0);
   RecalcUOFunc(0);
  }
 }

 int32_t clocks = run_time;
 int32_t running_timestamp = lastts;

 while(clocks > 0)
 {
  int32_t chunk_clocks = clocks;

  if(vol_update_counter > 0 && chunk_clocks > vol_update_counter)
   chunk_clocks = vol_update_counter;

  running_timestamp += chunk_clocks;
  clocks -= chunk_clocks;

  if(lfo_on)
   UpdateSubLFO(running_timestamp);
  else
   UpdateSubNonLFO(running_timestamp);

  if(vol_update_counter > 0)
  {
   vol_update_counter -= chunk_clocks;
   if(!vol_update_counter)
   {
    const int phase = vol_update_which & 1;
    const int lr = ((vol_update_which >> 1) & 1) ^ 1;
    const int chnum = vol_update_which >> 2;

    if(!phase)
    {
     //printf("Volume update(Read, %d since last): ch=%d, lr=%d, ts=%d\n", running_timestamp - last_read, chnum, lr, running_timestamp);

     if(chnum < 6)
     {
      vol_update_vllatch = GetVL(chnum, lr);
     }
     //last_read = running_timestamp;
    }
    else
    {
     // printf("Volume update(Apply): ch=%d, lr=%d, ts=%d\n", chnum, lr, running_timestamp);
     if(chnum < 6)
     {
      channel[chnum].vl[lr] = vol_update_vllatch;
     }
     //last_apply = running_timestamp;
    }
    vol_update_which = (vol_update_which + 1) & 0x1F;

    if(vol_update_which)
     vol_update_counter = phase ? 1 : 255;
    else if(vol_pending)
    {
     vol_update_counter = phase ? 1 : 255;
     vol_pending = false;
    }
   }
  }

  lastts = running_timestamp;
 }
}

void PCE_PSG::ResetTS(int32_t ts_base)
{
 lastts = ts_base;
 lasttsbase = ts_base;

 for(int chc = 0; chc < 6; chc++) {
  channel[chc].lastts = ts_base;
  channel[chc].lasttsbase = ts_base;
 }
}

void PCE_PSG::Power(const int32_t timestamp)
{
 // Not sure about power-on values, these are mostly just intuitive guesses(with some laziness thrown in).
 if(timestamp != lastts)
  Update(timestamp);

 // Don't memset channel to 0, there's stuff like lastts and blip_prev_samp that shouldn't be altered on Power().

 select = 0;
 globalbalance = 0;
 lfofreq = 0;
 lfoctrl = 0;

 for(int ch = 0; ch < 6; ch++)
 {
  channel[ch].frequency = 0;
  channel[ch].control = 0x00;
  channel[ch].balance = 0;
  memset(channel[ch].waveform, 0, 32);
  channel[ch].samp_accum = 0;

  channel[ch].waveform_index = 0;
  channel[ch].dda = 0x00;
  channel[ch].noisectrl = 0x00;
  
  channel[ch].vl[0] = 0x1F;
  channel[ch].vl[1] = 0x1F;

  channel[ch].samp_accum = 0;

  RecalcFreqCache(ch);
  RecalcUOFunc(ch);

  channel[ch].counter = channel[ch].freq_cache;

  if(ch >= 4)
  {
   RecalcNoiseFreqCache(ch);
  }
  channel[ch].noisecount = 1;
  channel[ch].lfsr = 1;
 }

 vol_pending = false;
 vol_update_counter = 0;
 vol_update_which = 0;
}