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21615 Discussions

FFT IFFT Unity gain output

Altera_Forum
Honored Contributor II
1,734 Views

Hello, 

I am using the DE2 board (cyclone II fpga) for my project.  

I took sound input using the internal audio codec (in 16 bit mode) then I pass it through FFT and then IFFT block. Finally i use the audio codec again to output the sound and hear it in the speaker.  

 

My problem is that, when i make the FFT IFFT pair unity gain, using a scalar block, always there is a audiable noise in the output. The fft window size i have used is 128.  

for scaling I followed the fft manual's procedure. I scale the output with the factor, 

 

exp_out = exp_fft + exp_ifft + 7; // 7 is for the window size. 

 

Should there always be a noise, when i scale? How to minimize it? 

 

Please help...
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Altera_Forum
Honored Contributor II
1,019 Views

my project is took sound to FFT but i dont give output to speaker.Ijust display it to VGA.can u give me your code so we can repair it?

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Altera_Forum
Honored Contributor II
1,019 Views

I am having trouble dealing with the scaler.v file to create my own scaler and implement it on FFT - IFFT block. I'm using DE2 board as well. Setting a 128 points and 16 bits. I am thinking that with the fft of 128 points and ifft of 128 points, we would get 256 points of the entire block. That makes the FFT engine to have a max of -11 to min of -3 by referring to Table A-1 on the FFT Megacore Function User Guide. However, I am still having hard time dealing with the scaling codes. Can anyone please help me out here?

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