ReconstructCoeffsInter

Reconstructs DCT coefficients for an inter coded block.

Syntax

IppStatus ippiReconstructCoeffsInter_H263_1u16s(Ipp8u** ppBitStream, int* pBitOffset, Ipp16s* pCoef, int* pIndxLastNonZero, int QP, int modQuantFlag);

Parameters

ppBitStream	Pointer to pointer to the current byte in the bitstream buffer. **ppBitStream is updated by the function.
pBitOffset	Pointer to the bit position in the byte pointed by *ppBitStream. Valid within the range 0 to 7. pBitOffset is updated by the function.
pCoef	Pointer to the output coefficients.
pIndxLastNonZero	Pointer to the index of the last non-zero coefficient in the scanning order. If an error is detected while decoding a coefficient, the index of the last decoded coefficient is returned in pIndxLastNonZero. If the block has no correctly decoded coefficients, pIndxLastNonZero is set to -1.
QP	Quantization parameter.
modQuantFlag	Flag equal to a non-zero value when Modified Quantization mode is in use, equal to 0 otherwise.

Description

The function ippiReconstructCoeffsInter_H263_1u16s is declared in the ippvc.h header file. This function performs decoding, dequantization, and inverse scan of the DCT coefficients for one inter coded block.

Inter DCT VLC decoding process is specified in [ITUH263], subclause 5.4.2 (Table 16), and is modified as specified in [ITUH263] Annex T, clause T.4, when Modified Quantization mode is in use. The dequantization process is specified in [ITUH263], subclause 6.2.1. When not in Modified Quantization mode, the output coefficients are clipped to the range [-2048, 2047] ([ITUH263], subclause 6.2.2). The DCT coefficients, encoded in the bitstream in the classical zigzag scan order ([ITUH263], Figure14), are reordered in the function into the normal order, that is, the order in which the coefficients are arranged on DCT output.

This function is used in the H.263 and MPEG-4 decoders included into Intel IPP Samples. See introduction to H.263.

Return Values

ippStsNoErr	Indicates no error.
ippStsNullPtrErr	Indicates an error condition if at least one of the specified pointers is NULL.
ippStsBitOffsetErr	Indicates an error condition if *pBitOffset is out of the range [0, 7].
ippStsVLCErr	Indicates an error condition if an illegal code is detected through the stream processing.
ippStsQPErr	Indicates an error condition if QP is out of the range [1, 31].