Computes the inverse Discrete Cosine Transform (DCT) of the input sequence DCT {X}. Wire data to the DCT {X} input to determine the polymorphic instance to use or manually select the instance.


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1D Inverse DCT

If y represents the input sequence DCT {X}, the one-dimensional inverse DCT of y is defined as:

and

where N is the length of the input sequence DCT {X}, y(k) is the k-th element of DCT {X}, and x(n) is the n-th element of the output sequence X. This VI applies a fast inverse DCT algorithm instead of calculating the inverse DCT directly. LabVIEW implements this fast inverse DCT algorithm using an FFT technique.

2D Inverse DCT

If y represents the input matrix DCT {X}, the two-dimensional inverse DCT of y is defined as:

where M and N are the number of rows and columns, respectively, of DCT {X}. x(m,n) is the element of the output matrix X with row number m and column number n. y(u,v) is the element of the input matrix DCT {X} with row number u and column number v. This VI performs a two-dimensional inverse DCT using the following two steps:

  1. Perform a one-dimensional inverse DCT row-by-row on the input matrix DCT {X}. The output is Y'.
  2. Perform a one-dimensional inverse DCT column-by-column on Y'. The output is X.

Examples

Refer to the following example files included with LabVIEW.

  • labview\examples\Signal Processing\Transforms\Image Compression with DCT.vi