DXVA_QmatrixData structure (dxva.h)

The DXVA_QmatrixData structure is sent by the host decoder to the accelerator to load inverse-quantization matrix data for off-host bitstream compressed video picture decoding.

Syntax

typedef struct _DXVA_QmatrixData {
  BYTE bNewQmatrix[4];
  WORD *Qmatrix[4][DXVA_USUAL_BLOCK_WIDTH  DXVA_USUAL_BLOCK_HEIGHT];
} DXVA_QmatrixData, *LPDXVA_QmatrixData;

Members

bNewQmatrix[4]

Indicates which new inverse-quantization matrices are present in an inverse-quantization matrix buffer. Each element in this array corresponds to an inverse-quantization matrix type and indicates whether a new inverse-quantization matrix of that type is present in the buffer. If any element in the bNewQmatrix array contains a value of 1, a new inverse-quantization matrix of the type specified for that array element follows in the inverse-quantization matrix buffer. The inverse-quantization matrices that can be used are as follows.

The value in bNewQmatrix[0] and bNewQmatrix[1] must not both be zero.

If the value for bNewQmatrix[2] or bNewQmatrix[3] is zero, then the following applies:

If bNewQmatrix[i - 2] is zero, the previous inverse-quantization matrix defined by the ith element must continue to be used by the accelerator.

If bNewQmatrix[i - 2] is 1, the inverse-quantization matrix defined by the ith element is set equal to the new inverse-quantization matrix for i - 2.

Qmatrix[4]

A two-dimensional array that specifies an inverse-quantization matrix buffer. This array is present only for each element in bNewQmatrix equal to 1. The matrix consists of (bBlockWidthMinus1+1) X (bBlockHeightMinus1+1) unsigned words (in which only the lower 8 bits of each word are used for the dominant video coding standards), where bBlockWidthMinus1 and bBlockHeightMinus1 are members of the DXVA_PictureParameters structure.

Remarks

If the video coding does not need inverse-quantization matrices (for example, H.261 and H.263), inverse-quantization matrix buffers must not be sent. If the video coding does need inverse-quantization matrices, some value must be provided for these inverse-quantization matrices by the host prior to, or in conjunction with, the transfer of any bitstream data buffers at the start of the video decoding process.

No default values of inverse-quantization matrices may be assumed by the accelerator in the absence of any prior value sent by the host. The quantization matrix values must be sent explicitly, even if they contain values that are available by default in the relevant video coding specification.

Inverse-quantization matrix buffers are sent only when the bConfigBitstreamRaw member of the DXVA_ConfigPictureDecode structure is 1.

The order of the data values within the inverse-quantization matrix is as specified in the relevant video coding specification.

Requirements

See also

DXVA_ConfigPictureDecode

DXVA_PictureParameters