TVec.IDCT Method — Dew Math

Overload List

#	Signature	Description
1	TVec IDCT	Calculate the inverse DCT in-pllace.
2	TVec IDCT(TVec Vec)	The inverse discrete cosine transform (DCT).
3	TMtxVec IDCT(TMtxVec Vec, Int32 VecIndex, Int32 Index, Int32 Len)	The inverse discrete cosine transform (DCT).

Overload 1: TVec IDCT

Calculate the inverse DCT in-pllace.

Result: stored in self (calling object), returns self for chaining

Remarks:

The length of the calling vector is adjusted automatically.

Overload 2: TVec IDCT(TVec Vec)

The inverse discrete cosine transform (DCT).

#	Name	Type	Description
1	Vec	TVec	source TVec

Result: stored in self (calling object), returns self for chaining

Remarks:

Calculates the inverse discrete cosine transform (DCT) of a Vec and writes the results in the calling vector. If Vec Dew.Math.TMtxVecBase.Length is a power of 2, the function uses an efficient algorithm that is significantly faster than the direct computation of DCT. For other values of Vec length, this function uses the direct formulas given below; however, the symmetry of cosine function is taken into account, which allows to perform about half of the multiplication operations in the formulas. In the following definition of inverse DCT, N=Vec.Length and V is the calling vector:

\begin{aligned} C(k) &= \begin{cases} \sqrt{\frac{1}{N}} & k=0 \\ \sqrt{\frac{2}{N}} & k > 0 \end{cases} \\ \text{V}[k] &= C(k)\cdot \text{Vec}[k]\sum _{n=0} ^{N-1} \cos \left( \frac{(2n+1)k\pi}{2N}\right) \end{aligned}

Examples

TVec a;
TVec b;
MtxVec.CreateIt(out a, out b);
try
    {
        a.SetIt(false,new double[] {1,-2,3,4});
        b.IDCT(a);
    }
finally
    {
        MtxVec.FreeIt(ref a, ref b);
    }

See Also: TVec.DCT

Overload 3: TMtxVec IDCT(TMtxVec Vec, Int32 VecIndex, Int32 Index, Int32 Len)

The inverse discrete cosine transform (DCT).

#	Name	Type	Description
1	Vec	TMtxVec	source TVec or TMtx
2	VecIndex	Int32
3	Index	Int32	start index
4	Len	Int32	element count

Result: stored in self (calling object), returns self for chaining

Remarks:

Calculate the inverse discrete cosine transform (DCT) from Vec elements [VecIndex]..[VecIndex+Len-1] and store the results in the calling object elements [Index]..[Index+Len-1]. The Len parameter must be the power of two. Size and Dew.Math.TMtxVec.Complex properties of the calling vector must be set explicitly. An exception is raised if Dew.Math.TMtxVecBase.ConditionCheck is True and array borders are overrun.