Learning Core Audio with Book Sample Code not working

Question

Hello I am trying to learn core audio farm this book:http://www.amazon.com/Learning-Core-Audio-Hands-On-Programming/dp/0321636848

But when I try to run this code:

      #import <Foundation/Foundation.h>
     #import <AudioToolbox/AudioToolbox.h>

#define SAMPLE_RATE 44100
 #define DURATION 5
  #define FILENAME_FORMAT @"%0.03f-test.aif"

  int main(int argc, const char * argv[])
 {

@autoreleasepool
{
    if(argc<2)
        return -1;

    double hz = 44;
    assert(hz>0);
    NSLog(@"Generating hz tone:%f",hz);

    NSString* fileName = [NSString stringWithFormat:FILENAME_FORMAT, hz];
    NSString* filePath = [[[NSFileManager defaultManager]currentDirectoryPath]
                          stringByAppendingPathComponent:fileName];
    NSURL* fileURL = [NSURL fileURLWithPath:filePath];


    AudioStreamBasicDescription asbd;
    memset(&asbd, 0, sizeof(asbd));
    asbd.mSampleRate = SAMPLE_RATE;
    asbd.mFormatID = kAudioFormatLinearPCM;
    asbd.mFormatFlags = kAudioFormatFlagIsBigEndian | kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
    asbd.mBitsPerChannel = 16;
    asbd.mChannelsPerFrame = 1;
    asbd.mFramesPerPacket = 1;
    asbd.mBytesPerFrame = 2;
    asbd.mBytesPerPacket = 2;


    AudioFileID audioFile;
    OSStatus audioErr = noErr;
    audioErr = AudioFileCreateWithURL((__bridge CFURLRef)fileURL, kAudioFileAIFFType, &asbd, kAudioFileFlags_EraseFile, &audioFile);
    assert(audioErr == noErr);

    long maxSampleCount = SAMPLE_RATE * DURATION;
    long sampleCount = 0;
    UInt32 bytesToWrite = 2;
    double waveLengthInSamples = SAMPLE_RATE / hz;

    while(sampleCount < maxSampleCount)
    {
        for(int i=0;i<waveLengthInSamples;i++)
        {
            SInt16 sample;
            if(i<waveLengthInSamples/2)
                sample = CFSwapInt16BigToHost(SHRT_MAX);
            else
                sample = CFSwapInt16BigToHost(SHRT_MIN);

            audioErr = AudioFileWriteBytes(audioFile, false, sampleCount*2, &bytesToWrite, &sample);
            assert(audioErr = noErr);
            sampleCount++;
        }
    }

    audioErr = AudioFileClose(audioFile);
    assert(audioErr = noErr);


}
return 0;

}

The program exit with this error code: Program ended with exit code: 255

Can anyone help me? I downloaded the sample code and the the same error occurs. I am using xcode 5 and a 64bit macbook. Thanks for your help.

Answer 1

It looks like you've modified the book's code to explicitly set the tone to 44Hz.

double hz = 44;

However, the original code expected you to input the tone as a command line parameter. These lines are checking for that parameter, and return -1 (or 255) when no parameter is found.

if(argc<2)
    return -1;

Remove those two lines to remove the parameter check.