Talk:Discrete cosine transform

From Wikipedia, the free encyclopedia

[edit] Change in notation

I have started converting the notation in this article to match the changes that have been made to Discrete Fourier transform . The four changes are:

1. n becomes N: Change all instances of the symbol n to the new symbol N to represent the length of the sequences in both the time and frequency domains.

2. k becomes n: Change all instances of the symbol k to the new symbol n to represent the index variable for the time domain sequence.

3. j becomes k: Change all instances of the symbol j to the new symbol k to represent the index variable for the frequency domain sequence.

4. f becomes X: Change all instances of the symbol f to the new symobl X to represent the transformation of the data sequence in the frequency domain.

For more information, see Talk:Discrete Fourier transform.

-- Metacomet 16:09, 6 January 2006 (UTC)

I just tried typing in the formula for the DCT 2 and 3 into my compiler to see what would happen. It wasn't inverting properly. It looks like it should be $-\frac{1}{2} x_0$ instead of positive. Adding in the negative sign made it work for me.

Nope, you must have mistyped them, or have a bug in your program. (To see that your proposed minus sign isn't correct, consider the simple case of a transform of all 1's.) —Steven G. Johnson 22:15, 1 September 2006 (UTC)

[edit] less algebra, and more explanation please

This article is pretty poor IMHO. How about explaining what it is without resorting to algebra, and also explaining its applications... --Rebroad 10:21, 19 November 2006 (UTC)

Sorry, if you don't even know algebra you have no hope of understanding a DCT. Don't blame the article for your own limitations. —Steven G. Johnson 20:18, 19 November 2006 (UTC)

[edit] DCT for non-uniform distributed data points

Is it possible to compute a DCT if the data points are non-uniformly distributed? i.e. if I only know the function x(t) values at t=0.0, 0.1, 0.4, 0.5, 0.55, 1.0 or so? I don't want to interpolate to artificial data points to get uniform distributed data points. --89.49.215.47 20:09, 26 November 2006 (UTC) (de:Benutzer:RokerHRO)