QuantFwdTableInit

Prepares quantization tables suitable for fast encoding.

Syntax

IppStatus ippiQuantFwdTableInit_JPEG_8u16u(const Ipp8u* pQuantRawTable, Ipp16u* pQuantFwdTable);

Parameters

pQuantRawTable	Pointer to the raw quantization table.
pQuantFwdTable	Pointer to the quantization table for the encoder.

Description

The function ippiQuantFwdTableInit_JPEG is declared in the ippj.h file. This function prepares quantization table in a format that is suitable for fast encoding. Initial raw quantization tables have zigzag order by definition. This function performs reordering transformation that converts the zigzag sequence of table elements to conventional order (left-to-right, top-to-bottom). To avoid division during quantization, the function ippiQuantFwdTableInit_JPEG scales the array by 15 bits. The pointer pQuantRawTable points to the array of 64 elements as is required by [ISO10918], Annex B.2.4.1, Quantization Table Specification Syntax. The pointer pQuantFwdTable points to an array containing 64 values of Ipp16u type.

Example “Using Intel IPP for Quantization of 8x8 Block of DCT Coefficients” and Example “Using Combined DCT Functions” show how to use the function ippiQuantFwdTableInit_JPEG_8u16u.

Return Values

ippStsNoErr	Indicates no error.
ippStsNullPtrErr	Indicates an error condition if one or both of the specified pointers are NULL.