使用書籍樣本代碼學習核心音頻不起作用

Question

您好，我正在嘗試學習核心音頻服務器這本書： http : //www.amazon.com/Learning-Core-Audio-Hands-On-Programming/dp/0321636848

但是當我嘗試運行此代碼時：

      #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;

}

程序退出，並顯示以下錯誤代碼：程序結束於退出代碼：255

誰能幫我？ 我下載了示例代碼，並發生了相同的錯誤。 我正在使用xcode 5和64位Macbook。 謝謝你的幫助。

Answer 1

您似乎已修改了本書的代碼，以將音調顯式設置為44Hz。

double hz = 44;

但是，原始代碼希望您將音調作為命令行參數輸入。 這些行正在檢查該參數，如果找不到參數，則返回-1（或255）。

if(argc<2)
    return -1;

刪除這兩行以刪除參數檢查。