Posted: 9/17/2011 6:13 PM
Post subject: ask the FCEUX source code
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Joined: 9/17/2011
Posts: 1
Now i study the part of FCEU Sound source code, i do not known the follow code mean, help! 
1.   fhinc=PAL?16626:14915;  // *2 CPU clock rate
      //#define NTSC_CPU 1789772.7272727272727272
      //#define PAL_CPU  1662607.125
I think 16626 is not correct. When PAL == 1: 14915/2/1789772 = 1/240 s When PAL == 0: 16626/2/1662607 = 1/200 s 
2.   soundtsinc=(uint32)((uint64)(PAL?(long double)PAL_CPU*65536:(long double)NTSC_CPU*65536)/(FSettings.SndRate * 16));
I don't known "soundtsinc" is used to do. 
void SetSoundVariables(void)
{
  int x;  
  fhinc=PAL?16626:14915;  // *2 CPU clock rate
  fhinc*=24;

  if(FSettings.SndRate)
  {
   wlookup1[0]=0;
   for(x=1;x<32>>=4;
   }
   wlookup2[0]=0;
   for(x=1;x<203>>=4;
   }
   if(FSettings.soundq>=1)
   {
    DoNoise=RDoNoise;
    DoTriangle=RDoTriangle;
    DoPCM=RDoPCM;
    DoSQ1=RDoSQ1;
    DoSQ2=RDoSQ2;
   }
   else
   {
    DoNoise=DoTriangle=DoPCM=DoSQ1=DoSQ2=Dummyfunc;
    DoSQ1=RDoSQLQ;
    DoSQ2=RDoSQLQ;
    DoTriangle=RDoTriangleNoisePCMLQ;
    DoNoise=RDoTriangleNoisePCMLQ;
    DoPCM=RDoTriangleNoisePCMLQ;
   }
  }  
  else
  {
   DoNoise=DoTriangle=DoPCM=DoSQ1=DoSQ2=Dummyfunc;
   return;
  }

  MakeFilters(FSettings.SndRate);

  if(GameExpSound.RChange)
   GameExpSound.RChange();

  nesincsize=(int64)(((int64)1<<17)*(double)(PAL?PAL_CPU:NTSC_CPU)/(FSettings.SndRate * 16));
  memset(sqacc,0,sizeof(sqacc));
  memset(ChannelBC,0,sizeof(ChannelBC));

  LoadDMCPeriod(DMCFormat&0xF);  // For changing from PAL to NTSC

  //（cpu_freq*65536）/（sample_rate*16）
  soundtsinc=(uint32)((uint64)(PAL?(long double)PAL_CPU*65536:(long double)NTSC_CPU*65536)/(FSettings.SndRate * 16));
}