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Baluncore

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You need to keep the signal in range on the screen. Can you display more than 8 bit data?

If your output is to be in dB then you might take the log (to the base two) of the 23 bit number.

If your output must be linear you will need to search for the maximum and scale the dataset.

display(i) = 255 * value(i) / maximum.

The process gain of the transform will increase the dynamic range of the output spectrum by the square root of the number of input samples.

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Thanks for the reply! I was going for something similar, thing is my dataset is dynamic which means my maximum will change in real time, I suppose the easy solution is to always output the last 8 bits, am I correct?

You need to keep the signal in range on the screen. Can you display more than 8 bit data?

If your output is to be in dB then you might take the log (to the base two) of the 23 bit number.

If your output must be linear you will need to search for the maximum and scale the dataset.

display(i) = 255 * value(i) / maximum.

The process gain of the transform will increase the dynamic range of the output spectrum by the square root of the number of input samples.

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Baluncore

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You could just display the most significant 8 bits but you will be throwing away much of your data.I suppose the easy solution is to always output the last 8 bits, am I correct?

If you do not have a fast multiply function then, rather than tracking the maximum, consider doing a 23 bit OR of all the data values into a common register that started out zero. After the accumulate, the first set bit will tell you how many bits to shift the output to show the most useful 8 bits.

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sophiecentaur

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For really drastic bit reduction is could be worth using floating point arithmetic.

Hardly 'without distortions' but what level of distortion would be acceptable?so I get the correct shape of the function without distortions.

You could always low pass filter the high res data, which would reduce apparent distortion.

There are so many possibilities but the best one would depend upon your actual requirement and what complexity (and delay) you can accept for the processing.

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marcusl

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Baluncore

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This appears to be a Fourier Synthesis exercise, computed in hardware using integers only.I'm trying to build a system that recieves coefficients and performs a Fourier approximation,

Unless there is some intelligent control of the integer input coefficients, the output amplitude will need to be scaled.

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sophiecentaur

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Raised Cos analysis is what's done for video bit reduction. I think it's chosen for speed and for the subjective qualities of the result (relevant here). There is a load of stuff about MPEG coding and its history (and Jpeg, too). The questions of scaling, blocking and interpolation have all been addressed since digital transmission of sound and vision have been implemented. No need to reinvent a wheel, I think.This appears to be a Fourier Synthesis exercise, computed in hardware using integers only.

Unless there is some intelligent control of the integer input coefficients, the output amplitude will need to be scaled.

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Baluncore

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I thought that this was an introductory exercise in VHDL. There was no OP mention of fast transform algorithms or data compression.No need to reinvent a wheel, I think.

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sophiecentaur

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I think there is problem here with terminology and definitions in the OP. As usual on PF, the terms were picked up and run with before the OP made it clear what was actually wanted. For instance, what is meant by "sampling a 23 bit number"?There was no OP mention of fast transform algorithms or data compression

Data compression must be involved here if the OP also requires "downsampling" and a reduction in bits (per sample??). You can downsample many signals without loss if you are prepared to use more bits per sample

It would help if the task were defined more clearly. It is probably a very specific thing that the OP has been given.

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