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DXVA_AYUVsample2 structure (dxva.h)

  • Article

The DXVA_AYUVsample2 structure is sent by the host decoder to the accelerator to specify Y, Cb, Cr color values, and an associated opacity.

Syntax

typedef struct _DXVA_AYUVsample2 {
  BYTE bCrValue;
  BYTE bCbValue;
  BYTE bY_Value;
  BYTE bSampleAlpha8;
} DXVA_AYUVsample2, *LPDXVA_AYUVsample2;

Members

bCrValue

Specifies a chrominance (Cr) sample value (scaled per ITU-R Rec. BT.601) as an unsigned value. Thus, the color black is nominally specified by Y=16, Cb=Cr=128, and the color white is nominally specified by Y=235, Cb=Cr=128.

bCbValue

Specifies a chrominance (Cb) sample value (scaled per ITU-R Rec. BT.601) as an unsigned value. Thus, the color black is nominally specified by Y=16, Cb=Cr=128, and the color white is nominally specified by Y=235, Cb=Cr=128.

bY_Value

Specifies a luminance (Y) sample value (scaled per ITU-R Rec. BT.601) as an unsigned value. Thus, the color black is nominally specified by Y=16, Cb=Cr=128, and the color white is nominally specified by Y=235, Cb=Cr=128.

bSampleAlpha8

Specifies the opacity of the pixel when used as a source graphic for blending with another picture. For Windows Server 2003 SP1 and Windows XP SP2, the opacity level is not used and should be ignored by the driver.

Remarks

A value of zero for bSampleAlpha8 indicates that the pixel is transparent (so that the other entries have no effect on the resulting blended picture), and a value of 255 indicates that the pixel is opaque (so that the other entries completely determine the value of the resulting blended picture sample).

For nonzero values of bSampleAlpha8, the blend to use is calculated by the following expression:

( ( ( (bSampleAlpha8+1) x (graphic value) ) + ( (255 - bSampleAlpha8) x (picture value) ) ) + 128 ) >> 8

For a zero value of bSampleAlpha8, the specified blend to use is the picture value without alteration.

Note   If the alpha-blending surface originates as a DVD video subpicture, the preferred method for converting from the 4-bit alpha used by DVD video to the 8-bit alpha specified by bSampleAlpha8 is to map a 4-bit alpha value of zero to an 8-bit alpha value of zero and to convert all nonzero 4-bit alphas to 8-bit alphas by performing a left shift of four places and adding the constant 15.
 
The width and height of the AYUV alpha-blending surface are specified in the associated buffer description list defined by the DXVA_BufferDescription structure.

The DXVA_AYUVsample2 structure is used for each sample in a DirectX VA AYUV blending surface, for OutsideYUVcolor in a DXVA_BlendCombination structure, and for each of the entries in a 16-entry AYUV alpha-blending palette.

Requirements

Requirement Value
Header dxva.h (include Dxva.h)

See also

DXVA_BlendCombination

DXVA_BufferDescription