Question

I’m extracting samples from an audio file in order to draw the wave form – I’ve generated an array with the samples ( waveDisplayArray in my code below ).

I wish to extract the largest value from this waveDisplayArray, what’s the best way to do this?

(I initally defined waveDisplayArray like this: int waveDisplayArray[280]={ 0 };
I’m not sure this is the best way to go about this)

thanks in advance 🙂

for( int y=0; y<convertedData.mNumberBuffers; y++ )
{
    NSLog(@"buffer# %u", y);
    AudioBuffer audioBuffer = convertedData.mBuffers[y];
    int bufferSize = audioBuffer.mDataByteSize / sizeof(Float32);
    Float32 *frame = audioBuffer.mData;
    NSLog(@"Buffer Size is: %i", bufferSize);

    int numberOfPixels = 280;
    int waveDisplayArray[280]={ 0 };
    int i;

    for (i = 0; i<numberOfPixels; i++)
    {
        //NSLog(@"i is: %i", i); 
        int j;
        int numberOfSamplesPerPixel = bufferSize/numberOfPixels;
        float average = 0;

        for (j=i*numberOfSamplesPerPixel; j<(i+1)*numberOfSamplesPerPixel; j++){

            average += frame[j];
            average = average/numberOfSamplesPerPixel;
        }

        waveDisplayArray[i] = average;
        NSLog(@"Average %i is %f",i,average);
        NSLog(@"waveDisplay Array %i: %f",i, waveDisplayArray[i]);
    }
}

Answer 1

I have edited and posted only relevant part to find the largest value.

int i;
float largest = 0;

for (i = 0; i<numberOfPixels; i++)
{
    //NSLog(@"i is: %i", i); 
    int j;
    int numberOfSamplesPerPixel = bufferSize/numberOfPixels;
    float average = 0;

    for (j=i*numberOfSamplesPerPixel; j<(i+1)*numberOfSamplesPerPixel; j++){

        average += frame[j];
        average = average/numberOfSamplesPerPixel;
    }

    waveDisplayArray[i] = average;

    if( largest < average )
    {
        largest = average;
    }

    NSLog(@"Average %i is %f",i,average);
    NSLog(@"waveDisplay Array %i: %f",i, waveDisplayArray[i]);

}
NSLog(@"Largest  %f",largest);