void FFTAccelerate::doFFTReal(float samples[], float amp[], int numSamples)
{
int i;
vDSP_Length log2n = log2f(numSamples);
int nOver2 = numSamples/2;
//-- window
//vDSP_blkman_window(window, windowSize, 0);
vDSP_vmul(samples, 1, window, 1, in_real, 1, numSamples);
//Convert float array of reals samples to COMPLEX_SPLIT array A
vDSP_ctoz((COMPLEX*)in_real,2,&A,1,nOver2);
//Perform FFT using fftSetup and A
//Results are returned in A
vDSP_fft_zrip(fftSetup, &A, 1, log2n, FFT_FORWARD);
// scale by 1/2*n because vDSP_fft_zrip doesn't use the right scaling factors natively ("for better performances")
{
const float scale = 1.0f/(2.0f*(float)numSamples);
vDSP_vsmul( A.realp, 1, &scale, A.realp, 1, numSamples/2 );
vDSP_vsmul( A.imagp, 1, &scale, A.imagp, 1, numSamples/2 );
}
//Convert COMPLEX_SPLIT A result to float array to be returned
/*amp[0] = A.realp[0]/(numSamples*2);
for(i=1;i<numSamples/2;i++)
amp[i]=sqrt(A.realp[i]*A.realp[i]+A.imagp[i]*A.imagp[i]);*/
// collapse split complex array into a real array.
// split[0] contains the DC, and the values we're interested in are split[1] to split[len/2] (since the rest are complex conjugates)
vDSP_zvabs( &A, 1, amp, 1, numSamples/2 );
}
Pitch PitchDetector::process(float *input, unsigned int numberOfSamples)
{
assert(this->numberOfSamples==numberOfSamples);
int n = numberOfSamples;
float *originalReal = this->FFTBuffer;
// 1.1.时域上加窗
vDSP_vmul(input, 1, this->windowFunc, 1, originalReal, 1, n);
// 分前后加窗没什么不一样啊
// vDSP_vmul(input, 1, this->windowFunc, 1, originalReal+(n/2), 1, n/2);
// vDSP_vmul(input+(n/2), 1, this->windowFunc+(n/2), 1, originalReal, 1, n/2);
// 2.拆成复数形似{1+2i, 3+4i, ..., 1023+1024i} 原始数组可以认为是（COMPLEX*）交错存储 现在拆成COMPLEX_SPLIT非交错（分轨式）存储
vDSP_ctoz((COMPLEX*)originalReal, 2, &this->A, 1, n/2); // 读取originalReal以2的步长塞进A里面
// // 3.fft变换的预设
float originalRealInLog2 = log2f(n);
// FFTSetup setupReal = vDSP_create_fftsetup(originalRealInLog2, FFT_RADIX2);
// 4.傅里叶变换
vDSP_fft_zrip(this->setupReal, &this->A, 1, originalRealInLog2, FFT_FORWARD);
// 5.转换成能量值
vDSP_zvabs(&this->A, 1, this->magnitudes, 1, n/2);
Float32 one = 1;
vDSP_vdbcon(this->magnitudes, 1, &one, this->magnitudes, 1, n/2, 0);
// 6.获取基频f0
float maxValue;
vDSP_Length index;
vDSP_maxvi(this->magnitudes, 1, &maxValue, &index, n/2);
// 6.1.微调参数
double alpha = this->magnitudes[index - 1];
double beta = this->magnitudes[index];
double gamma = this->magnitudes[index + 1];
double p = 0.5 * (alpha - gamma) / (alpha - 2 * beta + gamma);
// 7.转换为频率 indexHZ = index * (SampleRate / (n/2))
float indexHZ = (index+p) * ((this->sampleRate*1.0) / n);
// 8.乐理信息生成
Pitch pitch;
pitch.frequency = indexHZ;
pitch.amplitude = beta;
pitch.key = 12 * log2(indexHZ / 127.09) + 28.5;
pitch.octave = (pitch.key - 3.0) / 12 + 1;
calStep(&pitch);
pitch.stepString = calStep(indexHZ);
return pitch;
}