ReconstructCoeffsIntra

Reconstructs DCT coefficients for intra coded block.

Syntax

IppStatus ippiReconstructCoeffsIntra_H261_1u16s(Ipp8u** ppBitStream, int* pBitOffset, Ipp16s* pCoef, int* pIndxLastNonZero, int QP);

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.

Description

The function ippiReconstructCoeffsIntra_H261_1u16s is declared in the ippvc.h header file. This function performs decoding, dequantization, and inverse scanning of the DCT coefficients for one intra coded block.

DCT coefficients decoding and dequantization processes are specified in [ITUH261], subclause 4.2.4.1. The DCT coefficients, encoded in the bitstream in classical zigzag scan order ([ITUH261], Figure 12), 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.261 decoder included into Intel IPP Samples. See introduction to H.261.

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].
ippStsVLCCodeErr	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].