DXVA_ConfigPictureDecode structure

The DXVA_ConfigPictureDecode structure is sent by the host decoder to the accelerator to set the configuration for compressed picture decoding.

Syntax


typedef struct _DXVA_ConfigPictureDecode {
  DXVA_ConfigQueryOrReplyFunc dwFunction;
  DWORD                       dwReservedBits[3];
  GUID                        guidConfigBitstreamEncryption;
  GUID                        guidConfigMBcontrolEncryption;
  GUID                        guidConfigResidDiffEncryption;
  BYTE                        bConfigBitstreamRaw;
  BYTE                        bConfigMBcontrolRasterOrder;
  BYTE                        bConfigResidDiffHost;
  BYTE                        bConfigSpatialResid8;
  BYTE                        bConfigResid8Subtraction;
  BYTE                        bConfigSpatialHost8or9Clipping;
  BYTE                        bConfigSpatialResidInterleaved;
  BYTE                        bConfigIntraResidUnsigned;
  BYTE                        bConfigResidDiffAccelerator;
  BYTE                        bConfigHostInverseScan;
  BYTE                        bConfigSpecificIDCT;
  BYTE                        bConfig4GroupedCoefs;
} DXVA_ConfigPictureDecode, *LPDXVA_ConfigPictureDecode;

Members

dwFunction

Indicates the type of query or response when using probing and locking commands. The most significant 24 bits of dwFunction is the DXVA_ConfigQueryOrReplyFlag variable.

The least significant 4 bits of the DXVA_ConfigQueryOrReplyFlag variable contains status indicators for the query or response being performed.

The least significant 8 bits of dwFunction is the bDXVA_Func variable that, in this case, is equal to 1.

dwReservedBits

Reserved bits used for packing and alignment. These bits are zero.

guidConfigBitstreamEncryption

Indicates a GUID associated with the encryption protocol type for bitstream data buffers. The value DXVA_NoEncrypt (a GUID name defined in dxva.h) indicates that encryption is not applied. This is DXVA_NoEncrypt if bConfigBitstreamRaw is zero.

guidConfigMBcontrolEncryption

Indicates a GUID associated with the encryption protocol type for macroblock control buffers. The value DXVA_NoEncrypt (a GUID name defined in dxva.h) indicates that encryption is not applied. This is DXVA_NoEncrypt if bConfigBitstreamRaw is 1.

guidConfigResidDiffEncryption

Indicates a GUID associated with the encryption protocol type for residual difference decoding data buffers (buffers containing spatial-domain data or sets of transform-domain coefficients for accelerator-based IDCT). This is DXVA_NoEncrypt if bConfigBitstreamRaw is 1. (DXVA_NoEncrypt is a GUID defined in dxva.h that indicates encryption is not applied.)

bConfigBitstreamRaw

Contains the bitstream processing indicator. A value of 1 specifies that the picture data will be sent in bitstream buffers as raw bitstream content. A value of zero specifies that picture data will be sent using macroblock control command buffers.

This is zero if bConfigResidDiffHost is 1 or if bConfigResidDiffAccelerator is 1. The value zero is considered the basic level of support. The additional support of level one is preferred.

bConfigMBcontrolRasterOrder

Specifies whether macroblock control commands are in raster scan order or in arbitrary order. A value of 1 specifies that the macroblock control commands within each macroblock control command buffer are in raster scan order, and a value of zero indicates arbitrary order. Currently, a driver is allowed to restrict support to raster scan order; however, a driver should support both arbitrary and raster scan order.

bConfigResidDiffHost

Contains the host residual difference configuration (See Macroblock-Oriented Picture Decoding for more information). A value of 1 specifies that some residual difference decoding data may be sent as blocks in the spatial domain from the host. A value of zero specifies that spatial domain data will not be sent. This member is zero if bConfigBitstreamRaw is 1. It is preferred that an accelerator support both zero and 1.

bConfigSpatialResid8

Indicates the word size used to represent residual difference spatial-domain blocks for predicted (nonintra) pictures when using host-based residual difference decoding (when bConfigResidDiffHost is equal to 1).

If bConfigSpatialResid8 is 1 and bConfigResidDiffHost is 1, the host will send residual difference spatial-domain blocks for nonintra macroblocks using 8-bit signed samples, and for intra macroblocks in predicted (nonintra) pictures in a format depending on bConfigIntraResidUnsigned as follows:

  • If bConfigIntraResidUnsigned is zero, spatial-domain blocks for intra macroblocks are sent as 8-bit signed integer values relative to a constant reference value of 128.

  • If bConfigIntraResidUnsigned is 1, spatial-domain blocks for intra macroblocks are sent as 8-bit unsigned integer values relative to a constant reference value of zero.

If bConfigSpatialResid8 is zero and bConfigResidDiffHost is 1, the host will send residual difference spatial-domain blocks of data for nonintra macroblocks using 16-bit signed samples, and for intra macroblocks in predicted (nonintra) pictures in a format depending on bConfigIntraResidUnsigned as follows:

  • If bConfigIntraResidUnsigned is zero, spatial domain blocks for intra macroblocks are sent as 16-bit signed integer values relative to a constant reference value of 2(BPP-1), where BPP is the number of bits per sample for the uncompressed video (generally a value of 8).

  • If bConfigIntraResidUnsigned is 1, spatial domain blocks for intra macroblocks are sent as 16-bit unsigned integer values relative to a constant reference value of zero.

The bConfigSpatialResid8 member must be zero if bConfigResidDiffHost is zero. There is no preference for one particular value of bConfigSpatialResid8 when bConfigResidDiffHost is 1.

Note   For intra pictures with BPP equal to 8, spatial-domain blocks must be sent using 8-bit samples. For intra pictures with BPP greater than 8, spatial-domain blocks must be sent using 16-bit samples. (The BPP variable is the number of bits per sample for the uncompressed video, generally a value of 8.)

If bConfigIntraResidUnsigned is zero, these samples are sent as signed integer values relative to a constant reference value of 2(BPP-1). If bConfigIntraResidUnsigned is 1, these samples are sent as unsigned integer values relative to a constant reference value of zero.

 
bConfigResid8Subtraction

When equal to 1, indicates that 8-bit difference overflow blocks are subtracted rather than added. Must be zero unless bConfigSpatialResid8 is 1. The preferred value for an accelerator to support is 1 if bConfigSpatialResid8 is 1. The ability to subtract differences rather than to add them allows 8-bit difference decoding to be fully compliant with the full +/-255 range of values required in video decoder specifications. This is because +255 cannot be represented as the addition of two signed 8-bit numbers but any number in the range +/-255 can be represented as the difference between two signed 8-bit numbers (+255 is equal to +127 minus −128).

bConfigSpatialHost8or9Clipping

When equal to 1, indicates that spatial-domain blocks for intra macroblocks are clipped to an 8-bit range on the host and that spatial-domain blocks for nonintra macroblocks are clipped to a 9-bit range on the host. A value of zero indicates that no such clipping is performed by the host. Must be zero unless bConfigSpatialResid8 is equal to zero and bConfigResidDiffHost is equal to 1. The preferred value for an accelerator to support is zero.

bConfigSpatialResidInterleaved

When equal to 1, indicates that any spatial-domain residual difference data is sent in a chrominance-interleaved form matching the YUV format chrominance interleaving pattern. Must be zero unless bConfigResidDiffHost is 1 and the YUV format is NV12 or NV21. The preferred value for an accelerator to support is zero.

bConfigIntraResidUnsigned

Indicates the method of representation of spatial-domain blocks of residual difference data for intra blocks when using host-based difference decoding (when bConfigResidDiffHost is equal to 1).

When bConfigIntraResidUnsigned is equal to zero and bConfigResidDiffHost is equal to 1, spatial-domain residual difference data blocks for intra macroblocks are sent as follows:

  • In a nonintra picture if bConfigSpatialResid8 is zero, the spatial-domain residual difference data blocks for intra macroblocks are sent as 16-bit signed integer values relative to a constant reference value of 2(BPP-1), where BPP is the number of bits per sample for the uncompressed video (generally a value of 8).

  • In a nonintra picture if bConfigSpatialResid8 is 1 and in an intra picture if BPP is equal to 8 (regardless of the value of bConfigSpatialResid8), the spatial-domain residual difference data blocks for intra macroblocks are sent as 8-bit signed integer values relative to a constant reference value of 128.

When bConfigIntraResidUnsigned is equal to 1 and bConfigResidDiffHost is equal to 1, spatial-domain residual difference data blocks for intra macroblocks are sent as follows:

  • In a nonintra picture if bConfigSpatialResid8 is zero, the spatial-domain residual difference data blocks for intra macroblocks are sent as 16-bit unsigned integer values relative to a constant reference value of zero.

  • In a nonintra picture if bConfigSpatialResid8 is 1 and in an intra picture if BPP is equal to 8 (regardless of the value of bConfigSpatialResid8), the spatial-domain residual difference data blocks for intra macroblocks are sent as 8-bit unsigned integer values relative to a constant reference value of zero.

The bConfigIntraResidUnsigned member must be zero unless bConfigResidDiffHost is 1.

The preferred value for an accelerator to support is zero for bConfigIntraResidUnsigned.

bConfigResidDiffAccelerator

Contains the accelerator residual difference configuration. A value of 1 indicates that transform-domain blocks of coefficient data may be sent from the host for accelerator-based IDCT. A value of zero specifies that accelerator-based IDCT will not be used. If both bConfigResidDiffHost and bConfigResidDiffAccelerator are 1, some residual difference decoding will be done on the host and some on the accelerator, as indicated by macroblock-level control commands. This member must be zero if bConfigBitstreamRaw is 1.

The preferred value for an accelerator to support is 1 for bConfigResidDiffAccelerator.

When bConfigResidDiffAccelerator and bConfigResidDiffHost are equal to 1, residual difference decoding can be shared between the host and accelerator on a macroblock basis. This is considered an even higher level of accelerator capability than when bConfigResidDiffAccelerator is equal to 1 and bConfigResidDiffHost is equal to zero.

bConfigHostInverseScan

Indicates whether the inverse scan for transform-domain block processing is performed on the host or the accelerator. A value of 1 indicates that the inverse scan for transform-domain block processing will be performed on the host, and absolute indices will be sent instead for any transform coefficients. A value of zero indicates that inverse scan will be performed on the accelerator. This member must be zero if bConfigResidDiffAccelerator is zero or if bConfig4GroupedCoefs is 1.

The preferred value for an accelerator to support is 1 if bConfigResidDiffAccelerator is 1.

bConfigSpecificIDCT

Indicates the use of a specific IDCT method for off-host IDCT. A value of 1 indicates use of the IDCT specified in Annex W of ITU-T Recommendation H.263. A value of zero indicates that any compliant IDCT can be used for off-host IDCT. (Values other than zero and 1 are reserved for future use.)

This member must be zero if bConfigResidDiffAccelerator is zero (simply indicating host-based residual difference decoding).

Note   Annex W of ITU-T Recommendation H.263 does not comply with the IDCT requirements of MPEG-2 corrigendum 2 and thus bConfigSpecificIDCT must not be one for use with MPEG-2 video.
 
bConfig4GroupedCoefs

A value of 1 indicates that transform coefficients for off-host IDCT will be sent using the DXVA_TCoef4Group structure rather than the DXVA_TCoefSingle structure. This is zero if bConfigResidDiffAccelerator is zero or if bConfigHostInverseScan is 1.

The preferred value for an accelerator to support is zero if bConfigResidDiffAccelerator is 1.

Remarks

For some types of bitstreams, forcing macroblock control commands within each macroblock control command buffer to be in raster order either greatly increases the number of required buffers that must be processed or requires host reordering of the control information. Support of arbitrary order can thus be advantageous for the decoding process. For example, H.261 CIF-resolution decoding can require 36 macroblock control buffers per picture if raster scan order is necessary within each buffer (H.263 Annex K's arbitrary slice ordering and rectangular slice modes have more severe repercussions, possibly requiring an extremely large number of buffers.)

Requirements

Header

Dxva.h (include Dxva.h)

See also

DXVA_TCoef4Group
DXVA_TCoefSingle
DXVA_MBctrl_I_HostResidDiff_1
DXVA_MBctrl_I_OffHostIDCT_1
DXVA_MBctrl_P_HostResidDiff_1
DXVA_MBctrl_P_OffHostIDCT_1

 

 

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