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ZPlay::GetFFTData Method

Get FFT data for currently playing samples.

C++
virtual __stdcall int GetFFTData(int nFFTPoints, TFFTWindow nFFTWindow, int * pnHarmonicNumber, int * pnHarmonicFreq, int * pnLeftAmplitude, int * pnRightAmplitude, int * pnLeftPhase, int * pnRightPhase) = 0;
Parameters
Parameters 
Description 
int nFFTPoints 
Set this value to specify FFT size. This value must be power of 2. 
TFFTWindow nFFTWindow 
Set this value to specify FFT window. 
int * pnHarmonicNumber 
Pointer to variable receiving number of harmonics returned from FFT analysis. NumberOfHarmonics = (nFFTPoints/2 + 1) 
int * pnHarmonicFreq 
Pointer to integer array receiving frequency of each harmonic. User must to allocate memory for this array. Use returned pnHarmonicNumber value to get number of harmonics. If you don't need this information, set this parameter to NULL.
 
int * pnLeftAmplitude 
Pointer to integer array receiving amplitude of each harmonic for left channel. Amplitude range is from 0 to about 120 dB. User needs to allocate memory for this array. If you don't need this information, set this parameter to NULL. 
int * pnRightAmplitude 
Pointer to integer array receiving amplitude of each harmonic for right channel. Amplitude range is from 0 to about 120 dB. User needs to allocate memory for this array. If you don't need this information, set this parameter to NULL.
 
int * pnLeftPhase 
Pointer to integer array receiving phase of each harmonic for left channel. Phase range is from -90 to 90 degrees. User needs to allocate memory for this array. If you don't need this information, set this parameter to NULL.
 
int * pnRightPhase 
Pointer to integer array receiving phase of each harmonic for right channel. Phase range is from -90 to 90 degrees. User needs to allocate memory for this array. If you don't need this information, set this parameter to NULL.
 
Return Values
Return Values 
Description 
1 
All OK. 
0 
Error. To get error message read here. 
Remarks

nFFTPoints parameter specifies number of samples for FFT algorithm. This parameter must be power of 2. Larger value produces more harmonics and better frequency resolution. But this needs more processor power to calculate FFT algorithm. 

Note: NumOfHarmnics = NumOfFFTPoints/2 + 1 

Note: FFT data are fully synchronized with audio data from wave buffer. 

See Also
Example

Get amplitude values for left channel using 512 FFT points and triangular window. 

ZPlay C++ Class interface  

int nLeftAmplitude[257]; // we are using 512 FFT points: number of harmonics is 512/2 + 1 = 257
instance->GetFFTValues(512, fwTriangular, 0, 0,nLeftAmplitude, 0, 0, 0);

 

C Style interface 

int nLeftAmplitude[257]; // we are using 512 FFT points: number of harmonics is 512/2 + 1 = 257
zplay_GetFFTValues(instance, 512, fwTriangular, 0, 0,nLeftAmplitude, 0, 0, 0);
Group
Copyright (c) 2010. Zoran Cindori - All rights reserved.

Web: http://libzplay.sourceforge.net/

Email: zcindori@inet.hr

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