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我在使用vDSP实现FFT时遇到了困难.我理解这个理论,但我正在寻找一个特定的代码示例.

我有来自wav文件的数据如下:

问题1.如何将音频数据输入FFT？

问题2.如何从FFT中获取输出数据？

问题3.最终目标是检查低频声音.我该怎么做？

-(OSStatus)open:(CFURLRef)inputURL{
OSStatus result = -1;

result = AudioFileOpenURL (inputURL, 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, …