DCTQuantInv8x8LS

Performs dequantization, inverse DCT and level shift of an 8x8 block.

Syntax

IppStatus ippiDCTQuantInv8x8LS_JPEG_16s8u_C1R(const Ipp16s* pSrc, Ipp8u* pDst, int dstStep, const Ipp16u* pQuantInvTable);

IppStatus ippiDCTQuantInv8x8LS_JPEG_16s16u_C1R(const Ipp16s* pSrc, Ipp16u* pDst, int dstStep, const Ipp32f* pQuantInvTable);

Parameters

pSrc	Pointer to the 8x8 block of quantized DCT coefficients.
pDst	Pointer to the 8x8 block in the destination image.
dstStep	Distance in bytes between starts of consecutive lines in the destination image.
pQuantInvTable	Pointer to the quantization table for the decoder.

Description

The function ippiDCTQuantInv8x8LS_JPEG is declared in the ippj.h file. It operates with ROI (see Regions of Interest in Intel IPP).

This function performs an inverse DCT, dequantization of DCT coefficients and data conversion. The function ippiDCTQuantInv8x8LS_JPEG_16s8u_C1R converts data from the signed Ipp16s range [-128..127] to the unsigned Ipp8u range [0..255].

The function uses a quantization table suitable for fast decoding. This table must be prepared using the function ippiQuantInvTableInit_JPEG.

Return Values

ippStsNoErr	Indicates no error.
ippStsNullPtrErr	Indicates an error condition if any of the specified pointers is NULL.