SpectrogramRecorder various

[32Beat]

line 194: vDSP_ctoz((COMPLEX*) _A, 2, &(_compl_buf), 1, self.spectrumResolution);

The vDSP examples by apple seem to suggest that "self.spectrumResolution" should either be divided by 2, or the FFT should increase its log2 count by 1 (depending on the actual size of the buffer obv).
This also affects subsequent calls like vDSP_zaspec.
The documentation mentions that vDSP_DFT_Execute is preferred over the FFT variants, whenever possible.

[starzia]

Do you have a link to the examples and docs?

[32Beat]

https://developer.apple.com/library/mac/navigation/

type "vdsp" in the search field and you should end up with the latest and greatest:

The referencedoc entry for the fft routines will mention the DFT alternative, the vDSP example code has a lot of commenting that should clarify its use.

Note above the N/2 and LOG2N parameters.

For my own purposes I seem to get the best results using the DCT in lieu of either the DFT, or FFT.