DequantTransformResidual

Performs dequantization, integer inverse transformation, and shift for a 4x4 block of residuals.

Syntax

IppStatus ippiDequantTransformResidual_H264_16s_C1I(Ipp16s* pSrcDst, Ipp32s step, Ipp16s* pDC, Ipp32s AC, Ipp32s QP);

Parameters

pSrcDst

Pointer to the initial residual coefficients 4x4 block (AC luma or AC chroma or luma) and resultant transformed 4x4 block - source&destination array of size 16.

step

Distance in bytes between starts of the consecutive lines in the source/destination plane.

pDC

Pointer to the DC coefficient. If the case of luma block (not intra 16x16 macroblock type), pDC is set to NULL.

Flag that is not equal to zero, if at least one AC coefficient exists, and is equal to zero otherwise. In the case of luma block, which is not intra 16x16 macroblock type, AC should be:

0	if only pSrcDst[0] is not equal to 0 and other components are equal to 0
1	if any pSrcDst[i ] is non-zero (i is within range [1, 15])

Quantization parameter for luma or for chroma.

Description

The function ippiDequantTransformResidual_H264_16s_C1I is declared in the ippvc.h file and performs scaling, inverse transformation, and shift for a residual 4x4 block described in 8.5.8 of [JVTG050].

For transformation of a chroma block this function is called after TransformDequantChromaDC_H264. In the case of the 16x16 intra prediction mode, this function should be called after TransformDequantLumaDC_H264 for transforming a luma block.

If pDC is not equal to NULL, the function, before starting the scaling and transformation process, places the DC coefficient specified by pDC in the top left corner of the source/destination array, which is designated as c₀₀ in JVT-G050. Also during the scaling and transformation process the formula 8-266 ([JVTG050]) is used when calculating w₀₀.

If the pointer pDC is NULL, DC coefficient is dequantized like all the other coefficients. During the scaling and transformation process the formula 8-267 ([JVTG050]) is used when calculating w₀₀.

When calling the function, the argument QP, which is designated as qP in JVT-G050, should be calculated from the formulas 8-262 through 8-265 ([JVTG050]).

If AC is not equal to zero, formulas 8-278 through 8-277 ([JVTG050]) are applied to perform Inverse Transformations.

If AC = 0, all the coefficients are set equal to DC. The final shift is specified by formula 8-278.

Return Values

ippStsNoErr	Indicates no error.
ippStsNullPtrErr	Indicates an error condition if at least one of the specified pointers is NULL.
ippStsOutOfRangeErr	Indicates an error condition if QP is less than 1 or greater than 51.
ippStsStepErr	Indicates an error condition if srcStep value is less than 8.