2014/10/15 下午 10:11:10

iphone Programming Glossary: log2n

Using the apple FFT and accelerate Framework

http://stackoverflow.com/questions/3398753/using-the-apple-fft-and-accelerate-framework

actually make life any easier. Basically at the heart of it is vDSP_fft_zrip setupReal A stride log2n FFT_FORWARD vDSP_fft_zrip setupReal A stride log2n FFT_INVERSE FFT on n real floats and then reverse.. heart of it is vDSP_fft_zrip setupReal A stride log2n FFT_FORWARD vDSP_fft_zrip setupReal A stride log2n FFT_INVERSE FFT on n real floats and then reverse to get back to where we started. ip stands for in.. time duration of 1024 samples is ie 1 44 s. So we would pack A with 1024 floats from the mic set log2n 10 2^10 1024 precalculate some bobbins setupReal and vDSP_fft_zrip setupReal A stride log2n FFT_FORWARD..

Using the apple FFT and accelerate Framework

http://stackoverflow.com/questions/3398753/using-the-apple-fft-and-accelerate-framework

obscure it is generously commented but the comments don't actually make life any easier. Basically at the heart of it is vDSP_fft_zrip setupReal A stride log2n FFT_FORWARD vDSP_fft_zrip setupReal A stride log2n FFT_INVERSE FFT on n real floats and then reverse to get back to where we started. ip stands for in place which.. don't actually make life any easier. Basically at the heart of it is vDSP_fft_zrip setupReal A stride log2n FFT_FORWARD vDSP_fft_zrip setupReal A stride log2n FFT_INVERSE FFT on n real floats and then reverse to get back to where we started. ip stands for in place which means A gets overwritten That's the reason for all.. so that's ~44 frames sec. So our time window is whatever the time duration of 1024 samples is ie 1 44 s. So we would pack A with 1024 floats from the mic set log2n 10 2^10 1024 precalculate some bobbins setupReal and vDSP_fft_zrip setupReal A stride log2n FFT_FORWARD Now A will contain n 2 complex numbers. These represent..

iPhone Accelerate Framework FFT vs Matlab FFT

http://stackoverflow.com/questions/10820488/iphone-accelerate-framework-fft-vs-matlab-fft

Accelerate Reference vDSPRef Reference reference.html# apple_ref doc uid TP40009464 Objective C code int log2n log2f 16 FFTSetupD fftSetup vDSP_create_fftsetupD log2n kFFTRadix2 DSPDoubleSplitComplex fft_data fft_data.realp double.. apple_ref doc uid TP40009464 Objective C code int log2n log2f 16 FFTSetupD fftSetup vDSP_create_fftsetupD log2n kFFTRadix2 DSPDoubleSplitComplex fft_data fft_data.realp double malloc 8 sizeof double fft_data.imagp double malloc 8 sizeof.. double vDSP_ctoz COMPLEX ffx 2 fft_data 1 nOver2 split data 1 16 into odds and evens vDSP_fft_zrip fftSetup fft_data 1 log2n kFFTDirection_Forward fft forward vDSP_fft_zrip fftSetup fft_data 1 log2n kFFTDirection_Inverse fft inverse vDSP_ztoc fft_data..

Using the apple FFT and accelerate Framework

http://stackoverflow.com/questions/3398753/using-the-apple-fft-and-accelerate-framework

but the comments don't actually make life any easier. Basically at the heart of it is vDSP_fft_zrip setupReal A stride log2n FFT_FORWARD vDSP_fft_zrip setupReal A stride log2n FFT_INVERSE FFT on n real floats and then reverse to get back to where.. Basically at the heart of it is vDSP_fft_zrip setupReal A stride log2n FFT_FORWARD vDSP_fft_zrip setupReal A stride log2n FFT_INVERSE FFT on n real floats and then reverse to get back to where we started. ip stands for in place which means A.. is whatever the time duration of 1024 samples is ie 1 44 s. So we would pack A with 1024 floats from the mic set log2n 10 2^10 1024 precalculate some bobbins setupReal and vDSP_fft_zrip setupReal A stride log2n FFT_FORWARD Now A will contain..

iPhone FFT with Accelerate framework vDSP

http://stackoverflow.com/questions/6358764/iphone-fft-with-accelerate-framework-vdsp

NSLog NSString stringWithFormat @ Read d bytes d packets numBytesRead packetsRead return result FFT code below log2n N n 1 log2n stride 1 nOver2 n 2 printf 1D real FFT of length log2 d d n n n log2n Allocate memory for the input operands.. NSString stringWithFormat @ Read d bytes d packets numBytesRead packetsRead return result FFT code below log2n N n 1 log2n stride 1 nOver2 n 2 printf 1D real FFT of length log2 d d n n n log2n Allocate memory for the input operands and check its.. return result FFT code below log2n N n 1 log2n stride 1 nOver2 n 2 printf 1D real FFT of length log2 d d n n n log2n Allocate memory for the input operands and check its availability use the vector version to get 16 byte alignment. A.realp..

FFT on iPhone to ignore background noise and find lower pitches

http://stackoverflow.com/questions/7181630/fft-on-iphone-to-ignore-background-noise-and-find-lower-pitches

into even odd configuration vDSP_ctoz COMPLEX outputBuffer 2 A 1 nOver2 apply the fft vDSP_fft_zrip fftSetup A stride log2n FFT_FORWARD convert split real form to split vector vDSP_ztoc A 1 COMPLEX outputBuffer 2 nOver2 Demetri then goes on to..