如何从Tizen的实时FFT获得最准确的音频数据？ [英] How do I get most accurate audio frequency data possible from real time FFT on Tizen?

问题描述

目前正在使用Tizen IDE。

currently i m working on the Tizen IDE.

我已经从microPhone读取输入数据，并对其应用FFT ...但每次我获得nan输出。

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

这里是我的代码..

 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);

应用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;
}

推荐答案

> fft-> config 应该有一些关于FFT大小的参数，如2048,4096，即2的幂。如果增加这个值，你可以得到更高的频率分辨率。

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.

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