How to find the correct coefficients from matlab dct?

Hi,

I have performed a DCT on a signal and I want to create the original signal back by using the fourier co-efficients which I will get from DCT. But, I don't know how to do the correct normalization of the co-efficients.

Does someone know about it?

Thanks!

Answer 1

[Matt J]

If I assume you used dct to go forward, you should just be able to use idct to go back.

[Hassan Bhatti]

Yes, I can do that. But, I want to use the fourier co-efficients to do that, not the idct.

[Matt J]

But the DCT doesn't give you Fourier coefficients. It gives you DCT coefficients. It is true that the DCT iand IDCT are built on Fourier transforms, but any inversion you do that takes you from the DCT coefficients back to the original signal would have to end up being equivalent to the IDCT.

[Hassan Bhatti]

I have already tested FFT by getting the co-efficients out and putting it the fourier series back to get the original one. So, the same logic should be applicable for dct as well.

I have the co-efficients but just want to know how they are normalized?

[Matt J]

That depends. How did you implement the forward dct.