Kiss FFT bin幅度
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我已经花了很多时间研究FFT。使用KISSFFT尤其使我感兴趣，因为它是一种非常可移植的C实现。
我仍然不清楚如何将i [x]和r [x]转换为频率仓的幅度。因此创建了一个带符号的int 16版本的sin。我有512个罪恶样本。我希望看到一个Bin带有数据，其余的为零。不是啊
这是我的代码...
- (IBAction)testFFT:(id)sender{
NSLog(@\"testFFT\");
static double xAxis = 0;
static int sampleCount = 0;
static double pieSteps;
static double fullSinWave = 3.14159265*2;
static double sampleRate = 44100;
static double wantedHz = 0;
int octiveOffset;
char * globalString = stringToSend;
SInt16 dataStream[512];
// Notes: ioData contains buffers (may be more than one!)
// Fill them up as much as you can. Remember to set the size value in each buffer to match how
// much data is in the buffer.
for (int j = 0; j < 512; j++) {
wantedHz = 1000;
pieSteps = fullSinWave/(sampleRate/wantedHz);
xAxis += pieSteps;
dataStream[j] = (SInt16)(sin(xAxis) * 32768.0);
NSLog(@\"%d) %d\", j, dataStream[j]);
}
kiss_fft_cfg mycfg = kiss_fft_alloc(512,0,NULL,NULL);
kiss_fft_cpx* in_buf = malloc(sizeof(kiss_fft_cpx)*512);
kiss_fft_cpx* out_buf = malloc(sizeof(kiss_fft_cpx)*512);
for (int i = 0;i < 512;i++){
in_buf[i].r = dataStream[i];
in_buf[i].i = dataStream[i];
}
kiss_fft(mycfg,in_buf, out_buf);
for (int i = 0;i < 256;i++){
ix = out_buf[i].i;
rx = out_buf[i].r;
printfbar(sqrt(ix*ix+rx*rx)););
}
没有找到相关结果
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2 个回复
淘圃跺枯替
将有助于减少数字错误。会将输入缓冲区设置为，之前您已将其设置为ѭ4where，其中。 将移出循环看起来更好。 还有一个更基本的问题：您设置。采样率为44.1 kHz时，相当于。使用512点的缓冲区，您将在缓冲区中获得11.6个正弦波周期。非整数周期会导致泄漏。 但是，在进行此设置之前，尝试将ѭ9设置为正好在缓冲区中提供12个周期。您应该在变换中看到两个峰值：一个在索引12，一个在索引511-12。 您会看到两个峰值的原因是的变换是j*{-delta(w-w_0) - delta(w+w_0)}，缓冲区中的循环数为非整数。您应该看到一个以帐篷11和511-11为中心的宽帐篷形结果。您应将乘以窗口函数（Hann很好），以减少此效果的影响。挂帘妈乡
#include \"kiss_fft.h\" #include \"tools\\kiss_fftr.h\" #include <stdio.h> #include <conio.h> #define numberOfSamples 1024 int main(void) { struct KissFFT { kiss_fftr_cfg forwardConfig; kiss_fftr_cfg inverseConfig; kiss_fft_cpx* spectrum; int numSamples; int spectrumSize; } fft; static double dospi = 3.14159265*2; static double sampleRate = 44100; static double wantedHz = 0; int j,i,k; float dataStream[numberOfSamples]; float dataStream2[numberOfSamples]; float mags[numberOfSamples]; FILE * pFile; //Frequency to achive wantedHz = 9517; fft.forwardConfig = kiss_fftr_alloc(numberOfSamples,0,NULL,NULL); fft.inverseConfig = kiss_fftr_alloc(numberOfSamples,1,NULL,NULL); fft.spectrum = (kiss_fft_cpx*)malloc(sizeof(kiss_fft_cpx) * numberOfSamples); fft.numSamples = numberOfSamples; fft.spectrumSize = numberOfSamples/2+1; pFile = fopen (\"c:\\\\testfft.txt\",\"w\"); //filling the buffer data with a senoidal wave of frequency -wantedHz- and printing to testing it for (j = 0; j < numberOfSamples; j++) { dataStream[j] = 32768*(sin(wantedHz*dospi*j/sampleRate)); //Draw the wave form for (k=-64;k<(int)(dataStream[j]/512);k++) fprintf(pFile,\" \"); fprintf(pFile,\"*\\n\"); } //spectrum kiss_fftr(fft.forwardConfig, dataStream, fft.spectrum); //inverse just to testing kiss_fftri( fft.inverseConfig, fft.spectrum, dataStream2 ); for(i=0;i<fft.spectrumSize;i++) { mags[i] = hypotf(fft.spectrum[i].r,fft.spectrum[i].i); fprintf(pFile,\"[Sample %3d] ORIGINAL[%6.0f] -SPECTRUM[%5dHz][%11.0f]\",i,dataStream[i],i*(int)sampleRate/numberOfSamples,mags[i]); dataStream2[i] = dataStream2[i] / (float)fft.numSamples; fprintf(pFile,\" -INVERSE[%6.0f]\\n\",dataStream2[i]); } //end //free and close fclose (pFile); kiss_fft_cleanup(); free(fft.forwardConfig); free(fft.inverseConfig); free(fft.spectrum); getch(); return 0;