Problem with some arithmetic!

Hi again!!! ...I'm a little stuck here! I dont' really understand what this is doing...

Code:

---

 
  #define SAMPLE_RATE 22400

  float flangerDelay;
  static float sweepValue; /* delay changes depeding on current waveform value */
 
  /* Calculate the total current delay (in ms, not samples!) */
  flangerDelay = sweepValue + delay;
 
  /* calculate delay in samples rather than in time */
  tmp = flangerDelay * (float)(SAMPLE_RATE/1000);
 
  printf("flangerDelay: %f samples: %d\n", flangerDelay, tmp);

---

and the output...

Code:

---

...
...
flangerDelay: 0.500000 samples: 0
flangerDelay: 0.500000 samples: 0
flangerDelay: 0.500000 samples: 0
flangerDelay: 0.501000 samples: -1073741824
flangerDelay: 0.501000 samples: -1073741824
flangerDelay: 0.501000 samples: -1073741824
flangerDelay: 0.501000 samples: -1073741824
flangerDelay: 0.501000 samples: -1073741824
flangerDelay: 0.501000 samples: -1073741824
flangerDelay: 0.501000 samples: -1073741824
flangerDelay: 0.501000 samples: -1073741824
flangerDelay: 0.501000 samples: -1073741824
flangerDelay: 0.501000 samples: -1073741824
flangerDelay: 0.501000 samples: -1073741824
flangerDelay: 0.502000 samples: 1610612736
flangerDelay: 0.502000 samples: 1610612736
flangerDelay: 0.502000 samples: 1610612736
flangerDelay: 0.502000 samples: 1610612736
...
...

---

why if tmp = flangerDelay*(float)(SAMPLE_RATE/1000); is it printing out total crap? For the first samples it should be:

0.5 * (22400 / 1000) = 11.2

I'm very confused!!! anyone know whats going on???

you need to get sweepValue a value before using it in an expression.

e.g float sweepValue = 0;

also delay doesn't seem to have been defined.

If you replace your printf function with the following, what happens?

printf("flangerDelay: %f samples: %f\n", flangerDelay, tmp);

Full listing for function flanger()...

Code:

---

short int flanger(float range, float delay, int rate, short int inData){
 
  float flangerDelay; /* stores current delay required for flange effect */
  static int i=0;    /* keeps track of time for creating sweep waveform */
  static float sweepValue=0; /* keeps track of current sweep delay in ms */
  static int sweepFlag=1;    /* keeps track of waveform movement        */
  static int writePtr=0;    /* pointer to newest audio sample in buffer */
  static int readPtr=0;      /* pointer to oldest audio sample in buffer */
  float tmp; /* tmp value to see if dly will point to a position in buff */
 
  /* convert rate from Hz to Hz according to current sample rate    */
  /* NOTE: If it does not divise exact, take the integer part only! */
 
  /* is it time to change waveform? if not, increment counter */
  if (i >= rate) {
    /* has the maximum possible delay for sweep been reached? */
    if (sweepValue >= range)
      sweepFlag = 0; /* start the \ of triangular waveform */
    else if (sweepValue <= 0)
      sweepFlag = 1; /* start the / of triangular waveform */
   
    /* Is the waveform rising or falling? */
    if (sweepFlag==1)
      sweepValue += 0.001; /* increase sweep delay by .001 ms */
    else
      sweepValue -= 0.001; /* decrease sweep delay by .001 ms */

    /* reset i, to start count before waveform changes shape again */
    i=0;
  }
  else i++;
   
  /* Calculate the total current to delay (in ms, not samples!) */
  flangerDelay = sweepValue + delay;
 
  /* calculate delay in samples rather than in time */
  tmp = flangerDelay * 22.4f; //(float)(SAMPLE_RATE/1000);
 
  printf("flangerDelay: %f samples: %d\n", flangerDelay, tmp);

  /* Calculate position of the read & write pointers */
  if (writePtr < (int)tmp )
    readPtr = (((SAMPLE_RATE/1000)*MAX_DELAY) - ((int)tmp - writePtr));
  else
    readPtr = writePtr - (int)tmp;
   
  /* has the write pointer reached end of delay buffer? */
  if (writePtr > ((SAMPLE_RATE/1000)*MAX_DELAY))
    writePtr=0;
  else
    writePtr++;
 
  /* now add current audio sample to array and return oldest sample */
  delayArray[writePtr] = inData; 

  /* is tmp a whole value? i.e. will it point to a sample in the buffer? */
  if (tmp > (int)tmp){
    /* not a whole number! therefore, interpolation is required! */
        if (readPtr == ((SAMPLE_RATE/1000) * MAX_DELAY))
      return(calculateAverage(delayArray[readPtr],delayArray[0]));
        else
          return(calculateAverage(delayArray[readPtr],delayArray[readPtr+1]));
  }
  else {
    /* is a whole number! therefore, can take straight from buffer! */
    return delayArray[readPtr];
  }
 
} /* flanger() */

---

OK! Its fixed!!! I was being a dumbass!!! ...yes you were right! it was %f, but my flanger function.... if you see where the line:

if (readPtr == ((SAMPLE_RATE/1000) * MAX_DELAY))

This is obviously wrong because delayBuffer is defined as length [MAX_DELAY] - So I forgot to take one away!!!! ...by not doing this was giving a police siren effect!!!!


Thanks for everyones help!!!