我读过这些问题:iOS的FFT频谱抽奖
Using the Apple FFT and Accelerate Framework
How do I set up a buffer when doing an FFT using the Accelerate framework?
iOS FFT Accerelate.framework draw spectrum during playback
他们都描述了如何设置FFT与加速框架。在他们的帮助下,我能够设置fft并获得基本的频谱分析仪。现在,我显示了我从fft获得的所有值。但是,我只想显示10-15,或者可变数字的条形图,重现某些频率。就像iTunes或WinAmp液位计一样。 1.我是否需要平均一系列频率的幅度值?或者他们只是告诉你一个特定频率的大小? 2.另外,我是否需要将我的量值转换为db? 3.如何将我的数据映射到特定范围。我是否会针对最大分贝范围映射我的声音bitdepth?获取箱的最大值将导致跳跃最大映射值。
我RenderCallback:
static OSStatus PlaybackCallback(void *inRefCon,
AudioUnitRenderActionFlags *ioActionFlags,
const AudioTimeStamp *inTimeStamp,
UInt32 inBusNumber,
UInt32 inNumberFrames,
AudioBufferList *ioData)
{
UInt32 maxSamples = kAudioBufferNumFrames;
UInt32 log2n = log2f(maxSamples); //bins
UInt32 n = 1 << log2n;
UInt32 stride = 1;
UInt32 nOver2 = n/2;
COMPLEX_SPLIT A;
float *originalReal, *obtainedReal, *frequencyArray, *window, *in_real;
in_real = (float *) malloc(maxSamples * sizeof(float));
A.realp = (float *) malloc(nOver2 * sizeof(float));
A.imagp = (float *) malloc(nOver2 * sizeof(float));
memset(A.imagp, 0, nOver2 * sizeof(float));
obtainedReal = (float *) malloc(n * sizeof(float));
originalReal = (float *) malloc(n * sizeof(float));
frequencyArray = (float *) malloc(n * sizeof(float));
//-- window
UInt32 windowSize = maxSamples;
window = (float *) malloc(windowSize * sizeof(float));
memset(window, 0, windowSize * sizeof(float));
// vDSP_hann_window(window, windowSize, vDSP_HANN_DENORM);
vDSP_blkman_window(window, windowSize, 0);
vDSP_vmul(ioBuffer, 1, window, 1, in_real, 1, maxSamples);
//-- window
vDSP_ctoz((COMPLEX*)in_real, 2, &A, 1, maxSamples/2);
vDSP_fft_zrip(fftSetup, &A, stride, log2n, FFT_FORWARD);
vDSP_fft_zrip(fftSetup, &A, stride, log2n, FFT_INVERSE);
float scale = (float) 1.0/(2 * n);
vDSP_vsmul(A.realp, 1, &scale, A.realp, 1, nOver2);
vDSP_vsmul(A.imagp, 1, &scale, A.imagp, 1, nOver2);
vDSP_ztoc(&A, 1, (COMPLEX *) obtainedReal, 2, nOver2);
vDSP_zvmags(&A, 1, obtainedReal, 1, nOver2);
Float32 one = 1;
vDSP_vdbcon(obtainedReal, 1, &one, obtainedReal, 1, nOver2, 0);
for (int i = 0; i < nOver2; i++) {
frequencyArray[i] = obtainedReal[i];
}
// Extract the maximum value
double fftMax = 0.0;
vDSP_maxmgvD((double *)obtainedReal, 1, &fftMax, nOver2);
float max = sqrt(fftMax);
}
播放一些音乐,我从-96dB值到0dB。
CGPointMake(i, kMaxSpectrumHeight * (1 - frequencyArray[i]/-96.));
是给我的一个相当圆润的曲线: 在绘制一个点
如果我不转换为DB我可以通过我的10000阵列值乘以绘制并获得好的山峰。
我做得完全错误的?我怎样才能显示可变数量的酒吧?
只是想知道:但是你有最终的代码,呈现酒吧?我很难从下面的答案中知道要去哪里。 – kezi 2014-08-14 04:30:13