How do I get most accurate audio frequency data possible from real time FFT on Tizen?

问题

currently i m working on the Tizen IDE.

I had read the input data from the microPhone and apply the FFT on it... but everytime i gets the nan output.

here is my code..

 ShortBuffer *pBuffer1 = pData->AsShortBufferN();

fft = new KissFFT(BUFFER_SIZE);

std::vector<short> input(pBuffer1->GetPointer(),
        pBuffer1->GetPointer() + BUFFER_SIZE); // this contains audio data
std::vector<float> specturm(BUFFER_SIZE);

fft->spectrum(input, specturm);

applying FFT..

   void KissFFT::spectrum(KissFFTO* fft, std::vector<short>& samples2,
        std::vector<float>& spectrum) {


    int len = fft->numSamples / 2 + 1;

    kiss_fft_scalar* samples = (kiss_fft_scalar*) &samples2[0];

    kiss_fftr(fft->config, samples, fft->spectrum);

    for (int i = 0; i < len; i++) {

        float re = scale(fft->spectrum[i].r) * fft->numSamples;
        float im = scale(fft->spectrum[i].i) * fft->numSamples;

         if (i > 0)
         spectrum[i] = sqrtf(re * re + im * im) / (fft->numSamples / 2);
         else
         spectrum[i] = sqrtf(re * re + im * im) / (fft->numSamples);
         AppLog("specturm %d",spectrum[i]); // everytime returns returns nan output
    }

}



 KissFFTO* KissFFT::create(int numSamples) {

    KissFFTO* fft = new KissFFTO();
    fft->config = kiss_fftr_alloc(numSamples/2, 0, NULL, NULL);
    fft->spectrum = new kiss_fft_cpx[numSamples / 2 + 1];
    fft->numSamples = numSamples;

    return fft;
}

回答1:

In fft->config there should be some parameters about the size of FFT like 2048, 4096, i.e. powers of 2. If you increase this value, you can get more resolution in frequency.

来源：https://stackoverflow.com/questions/16931570/how-do-i-get-most-accurate-audio-frequency-data-possible-from-real-time-fft-on-t