H261_A

The H261_A restricted profile contains the set of features required for minimal support of ITU-T Rec. H.261 without acceleration support for H.261 Annex D graphics. Support of this profile is currently encouraged, but not required. This set of features is defined by the following restrictions.

Restrictions on DXVA_ConnectMode

The following restriction on the DXVA_ConnectMode structure applies when the bDXVA_Func variable defined by the dwFunction member of the DXVA_ConfigPictureDecode structure is equal to 1 (picture decoding).

Structure Member	Constant
wRestrictedMode	DXVA_RESTRICTED_MODE_H261_A

Restrictions on DXVA_PictureParameters

The following restrictions on the DXVA_PictureParameters structure apply when the bDXVA_Func variable defined by the dwFunction member of DXVA_ConfigPictureDecode is equal to 1.

Structure Member	Value
bBPPMinus1	7
bSecondField	Zero
bMacroblockWidthMinus1	15
bMacroblockHeightMinus1	15
bBlockWidthMinus1	7
bBlockHeightMinus1	7
bChromaFormat	1 (4:2:0)
bPicStructure	3 (frame structured)
bMVprecisionAndChromaRelation	2 (H.261 integer-sample motion)
bPicExtrapolation	Zero
bPicDeblocked	Zero
bPic4MVallowed	Zero
bPicOBMC	Zero
bMV_RPS	Zero
bPicScanFixed	1

Restrictions on DXVA_MBctrl_I_HostResidDiff_1, DXVA_MBctrl_I_OffHostIDCT_1, DXVA_MBctrl_P_HostResidDiff_1, and DXVA_MBctrl_P_OffHostIDCT_1

The following restrictions on the DXVA_MBctrl_I_HostResidDiff_1, DXVA_MBctrl_I_OffHostIDCT_1, DXVA_MBctrl_P_HostResidDiff_1, and DXVA_MBctrl_P_OffHostIDCT_1 structures apply when the bDXVA_Func variable defined by the dwFunction member of DXVA_ConfigPictureDecode is equal to 1.

Structure Member	Value
MotionType	2 (frame motion) if the MotionForward variable defined in the wMBtype member of these structures equals 1.
MBscanMethod	Zero (zigzag) if the bConfigHostInverseScan member of DXVA_ConfigPictureDecode equals zero.
FieldResidual	Zero (frame residual)
MotionBackward	Zero (no backward prediction)

Restrictions on Bitstream Buffers

The contents of any bitstream buffer must contain data in the H.261 video format.

This restriction applies when the bDXVA_Func variable defined by the dwFunction member of DXVA_ConfigPictureDecode is equal to 1.