如何在iPhone上执行WAV文件的FFT？

Question

我必须在iPhone应用程序中为.wav文件执行FFT.我已经看过那里的FFT算法,但是我如何解析WAV文件并在这样的算法中使用？

我应该将WAV文件转换为NSData还是其他什么？

以前有没有人在iPhone上成功执行过WAV文件的FFT？我尝试使用iPhoneFFT,没有成功.

例如,那里的代码

 // 2. Then fill up an array with data with your own function
   fillUpInputSignalWithMyData(myFFT.inputData);

我如何将WAV文件中的数据提供给这样的东西？

Answer 1

MyAudioFile  *audioFile = [[MyAudioFile alloc]init];
OSStatus result = [audioFile open:var ofType:@"wav"];
int numFrequencies=16384;
int kNumFFTWindows=10;

OouraFFT *myFFT = [[OouraFFT alloc] initForSignalsOfLength:numFrequencies*2 andNumWindows:kNumFFTWindows];
for(long i=0; i<myFFT.dataLength; i++)
{
myFFT.inputData[i] = (double)audioFile.audioData[i];
} 
[myFFT calculateWelchPeriodogramWithNewSignalSegment];
for (int i=0;i<=8192;i++) {
NSLog(@"the spectrum data %d is  %f ",i,myFFT.spectrumData[i]);

}

我创建了包含的MyAudioFile类

-(OSStatus)open:(NSString *)fileName ofType:(NSString *)fileType{
OSStatus result = -1;

CFStringRef filePath=fileName;

CFURLRef audioFileURL = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, (CFStringRef)filePath, kCFURLPOSIXPathStyle, false);
//open audio file
result = AudioFileOpenURL (audioFileURL, kAudioFileReadPermission, 0, &mAudioFile);
if (result == noErr) {
    //get  format info
    UInt32 size = sizeof(mASBD);

    result = AudioFileGetProperty(mAudioFile, kAudioFilePropertyDataFormat, &size, &mASBD);

    UInt32 dataSize = sizeof packetCount;
    result = AudioFileGetProperty(mAudioFile, kAudioFilePropertyAudioDataPacketCount, &dataSize, &packetCount);
    NSLog([NSString stringWithFormat:@"File Opened, packet Count: %d", packetCount]);

    UInt32 packetsRead = packetCount;
    UInt32 numBytesRead = -1;
    if (packetCount > 0) { 
        //allocate  buffer
        audioData = (SInt16*)malloc( 2 *packetCount);
        //read the packets
        result = AudioFileReadPackets (mAudioFile, false, &numBytesRead, NULL, 0, &packetsRead,  audioData); 
        NSLog([NSString stringWithFormat:@"Read %d  bytes,  %d packets", numBytesRead, packetsRead]);
    }
}
else
    NSLog([NSString stringWithFormat:@"Could not open file: %@", filePath]);


CFRelease (audioFileURL);     
return result;
}

那就是它.我正在获得功率谱阵列.我已经检查了样本正弦波.它工作正常.