I use the TI FFT Library and I have two question : First, in the TI example RFFT32_brev(ipcb,ipcb,N); RFFT32_brev(ipcb,ipcb,N);// Input...

I use the TI FFT Library and I have two question : First, in the TI example RFFT32_brev(ipcb,ipcb,N); RFFT32_brev(ipcb,ipcb,N);// Input samples in Real Part fft.win(&fft); RFFT32_brev(ipcb,ipcb,N); RFFT32_brev(ipcb,ipcb,N);// Input after windowing fft.calc(&fft); fft.split(&fft); fft.mag(&fft); There are 4 times "RFFT32_brev(ipcb,ipcb,N); ", I don't know why ? I deleted the last 3 l...

I would like to have a amplitude as well as a decibel display in my program of 16-bit stereo audio. 1) First I take the data from both...

I would like to have a amplitude as well as a decibel display in my program of 16-bit stereo audio. 1) First I take the data from both channels as L,R,L,R,etc and feed it into the FFT as one signal. 2) Next I seperate the FFT data into alternating left and right channels. For example Right = FFT[0], FFT[2], FFT[4]; Left = FFT[1], FFT[3], FFT[5]; 3) I take the left channel and perfor...

Hi all, I always hear that the computational complexity of FFT is O(NlogN). However I learn that there are many FFT algorithms such...

Hi all, I always hear that the computational complexity of FFT is O(NlogN). However I learn that there are many FFT algorithms such as: Cooley-Tukey FFT algorithm ,Split-radix FFT algorithm ,Prime-factor FFT algorithm ,Bruun's FFT algorithm ,,Rader's FFT algorithm ,Bluestein's FFT algorithm are they have the same computational complexity O(NlogN)?? Thanks

On 15 Dec 2009 12:46:41 GMT, Philip Pemberton wrote: > How would I go about converting this from an FFT to an inverse-FFT? For an...

On 15 Dec 2009 12:46:41 GMT, Philip Pemberton wrote: > How would I go about converting this from an FFT to an inverse-FFT? For an inverse FFT, just reverse the list of arguments. If r[n] and i [n] are two N point arrays for the real and imaginary inputs/outputs, and: FFT (r,i) is your forward FFT, then an inverse FFT is: FFT (i,r) You can scale after t

Hi Guys, I am doing a 256 point FFT in FPGA on High speed ADC data with a custom FFT core...Now i need to do a 4:1 overlap(64 points for 256...

Hi Guys, I am doing a 256 point FFT in FPGA on High speed ADC data with a custom FFT core...Now i need to do a 4:1 overlap(64 points for 256 FFT) on ADC data...that is first 256 point FFT will be done on sample no 1 to 256, next FFT on sample no 65 to 320 and so on...One solution is to use four such FFT cores to perform the operations..I want to know whether there is any other method/optimizati...

Hi. A simple question. Given a signal (17Hz) with noise (from external devices, environment, etc), and, say, 10 secs of data, in order to...

Hi. A simple question. Given a signal (17Hz) with noise (from external devices, environment, etc), and, say, 10 secs of data, in order to extract out the signal, which is better to do: a. take the entire 10 secs of data and do a FFT and see if we could see the 17 Hz sticking out b. take a 1 sec FFT of the signal for every 0.5 sec (FFT at 0-1, FFT at 0.5-1.5, FFT at 1-2, FFT at 1.5-2.5, e...

Hi guys, The Linearity property of Fourier transform says: z(t)=af1(t)+bf2(t) the linear combination of the terms is unaffected by...

Hi guys, The Linearity property of Fourier transform says: z(t)=af1(t)+bf2(t) the linear combination of the terms is unaffected by the transform. Z(?)=aF1(?)+bF2(?) and Z(?) = FFT{ z(t) }. I synthesised a signal, sn as follows. I want to remove the mean values in the signal. According to the Fourier transform property, FFT{x-mean(x)} = FFT{x}-FFT{mean(x)} the left

Hi guys, The Linearity property of Fourier transform says: z(t)=af1(t)+bf2(t) the linear combination of the terms is unaffected by...

Hi guys, The Linearity property of Fourier transform says: z(t)=af1(t)+bf2(t) the linear combination of the terms is unaffected by the transform. Z(?)=aF1(?)+bF2(?) and Z(?) = FFT{ z(t) }. I synthesised a signal, sn as follows. I want to remove the mean values in the signal. According to the Fourier transform property, FFT{x-mean(x)} = FFT{x}-FFT{mean(x)} the left

hi, can anyone tell me how to perform 2d fft? what i understood for 2d fft is that for each rows we perform individual fft's and place the...

hi, can anyone tell me how to perform 2d fft? what i understood for 2d fft is that for each rows we perform individual fft's and place the result on the respective rows and similarly for the columns. what i mean is suppose i have an array of 2d data as: 0000 0110 0110 0000 now what i am trying to do is calculate fft (4 point fft instead of 16 point fft) of the first row (0000) and ...

i am working on a FFT processor. i need to know that if i need to take the 1024 point FFT of a voltage time series then what should i do. i...

i am working on a FFT processor. i need to know that if i need to take the 1024 point FFT of a voltage time series then what should i do. i mean which one is correct way. 1) wait for 1024 samples and take their FFT. then wait for another 1024 samples and take their FFT and so on.... 2) wait for 1024 samples for the first time only and take their FFT. then after the computation of this FFT, i...

Hi, I have now a Java code implementing real FFT. I need actually Java code for implementing integer (fixed-point) FFT. I mean with this that...

Hi, I have now a Java code implementing real FFT. I need actually Java code for implementing integer (fixed-point) FFT. I mean with this that the FFT accepts Java int type as input and produces Java int type as output. If there is no Java fixed-point FFT, how can I convert the existing Java real FFT to a fixed-point FFT? Would please somebody give a code example in Java. PS: I can now perfor...

hi, can anyone tell me how to perform 2d fft? what i understood for 2d fft is that for each rows we perform individual fft's and place the...

hi, can anyone tell me how to perform 2d fft? what i understood for 2d fft is that for each rows we perform individual fft's and place the result on the respective rows and similarly for the columns. what i mean is suppose i have an array of 2d data as: 0000 0110 0110 0000 now what i am trying to do is calculate fft (4 point fft instead of 16 point fft) of the first row (0000) and plac...

Hello, I have a gaussian kernel of size [192,192] to be convoluted with an image of size [512,512] for smoothing. Using the FFT property that...

Hello, I have a gaussian kernel of size [192,192] to be convoluted with an image of size [512,512] for smoothing. Using the FFT property that fft of a convolution is the product of the fft of the individual terms (fft(f(t) * g(t))) = f(w)g(w), i could say that smoothedimage = fftinverse(fft(image) fft(kernel)) the problem i am encountering is this: straightforward convolution is easy b...

Hello !! I have to FFT a signal made of 0s and 1s, i.e., my sequence is for example, 0,1,1,0,0,0,0,1,0,1,1,0 ... etc This is a true serie of...

Hello !! I have to FFT a signal made of 0s and 1s, i.e., my sequence is for example, 0,1,1,0,0,0,0,1,0,1,1,0 ... etc This is a true serie of 0s and 1s, not a number, written as binary. I am wondering if someone knows about a FFT algorithm able to handle such a cose. I'm not (far not!) an expert in FFT algorithm, but I can imagine that such a "signal" to FFT should impact the FFT code. ...

Hi Has anyone written their own fft function for the dsPIC ? (NOT the supplied library fft). I need a fft for measuring signal in noise and...

Hi Has anyone written their own fft function for the dsPIC ? (NOT the supplied library fft). I need a fft for measuring signal in noise and not being a DSP person would prefer to implement it rather than write it from scratch. The dsPIC library scales the data by 1/N which limits the dynamic range of the fft. I can post scale and run the fft again until I have a usable number - its just ...

Hello, When combining two smaller FFTs to make a larger one, what are the techniques. Example..I want to combine two 64 pt FFTs into a 128 pt...

Hello, When combining two smaller FFTs to make a larger one, what are the techniques. Example..I want to combine two 64 pt FFTs into a 128 pt FFT. I have fed the first 64 data samples into the first FFT and the second 64 into the 2nd FFT. The results are output from the two FFTs into a 128 array. The problem is that the 128 pt FFT result has the same peaks as the 64 pt FFT. What is the problem ...

Hi, Suppose I have N samples and I want to do one N point FFT and a 4N point FFT with zeros padding. Can do get the 4N-FFT by...

Hi, Suppose I have N samples and I want to do one N point FFT and a 4N point FFT with zeros padding. Can do get the 4N-FFT by interpolating the N-FFT? Is there a formula? Is the interpolation fast than just do a zero-padded 4N-FFT? Thanks

I am sampling voltage values. I need to convert it to the frequency domain using FFT . As I understand the frequency steps after FFT will be the...

I am sampling voltage values. I need to convert it to the frequency domain using FFT . As I understand the frequency steps after FFT will be the integer multiples of Fs/N (where Fs is the data sample rate in Hz, and N is the FFT length). How can I have sub-Hz frequency steps? Do I use use long sampling times and long FFT lengths, for instance, Sampleing at 1 kHz and using 10000 FFT length will...

Dear All, I have a simple question regarding FFT based filtering. Most text tells us to do the FFT based filtering is multiplication of "FFT of...

Dear All, I have a simple question regarding FFT based filtering. Most text tells us to do the FFT based filtering is multiplication of "FFT of signal" and "FFT of FIR filter kernel." I understand that. My question is, in some simple situation, can we directly manipulate the frequency result of signal. For example, if do a low pass filtering, I obtained FFT of a signal, then just simply set ...

Hi all, I am interested in performing million-point FFT in FPGA. I've read some papers and concluded that the best way of performing...

Hi all, I am interested in performing million-point FFT in FPGA. I've read some papers and concluded that the best way of performing million-point FFT would be having multiple smaller size FFT in parallel, for example 8x 16K-point FFT, with twiddle factor multipliers (I think it will be radix-2^2 streaming FFT with multiple inputs) But, since I am a newbie in DSP, I want to check if there is a...