# Thread: Problem with some arithmetic!

1. ## 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???

2. 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.

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

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

4. 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

/* 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))
else
}
else {
/* is a whole number! therefore, can take straight from buffer! */
}

} /* flanger() */```

5. 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!!!