DXVA_PictureParameters structure (dxva.h)
The DXVA_PictureParameters structure is sent by the host decoder to the accelerator to provide the picture-level parameters of a compressed picture for decoding on the accelerator.
Syntax
typedef struct _DXVA_PictureParameters {
WORD wDecodedPictureIndex;
WORD wDeblockedPictureIndex;
WORD wForwardRefPictureIndex;
WORD wBackwardRefPictureIndex;
WORD wPicWidthInMBminus1;
WORD wPicHeightInMBminus1;
BYTE bMacroblockWidthMinus1;
BYTE bMacroblockHeightMinus1;
BYTE bBlockWidthMinus1;
BYTE bBlockHeightMinus1;
BYTE bBPPminus1;
BYTE bPicStructure;
BYTE bSecondField;
BYTE bPicIntra;
BYTE bPicBackwardPrediction;
BYTE bBidirectionalAveragingMode;
BYTE bMVprecisionAndChromaRelation;
BYTE bChromaFormat;
BYTE bPicScanFixed;
BYTE bPicScanMethod;
BYTE bPicReadbackRequests;
BYTE bRcontrol;
BYTE bPicSpatialResid8;
BYTE bPicOverflowBlocks;
BYTE bPicExtrapolation;
BYTE bPicDeblocked;
BYTE bPicDeblockConfined;
BYTE bPic4MVallowed;
BYTE bPicOBMC;
BYTE bPicBinPB;
BYTE bMV_RPS;
BYTE bReservedBits;
WORD wBitstreamFcodes;
WORD wBitstreamPCEelements;
BYTE bBitstreamConcealmentNeed;
BYTE bBitstreamConcealmentMethod;
} DXVA_PictureParameters, *LPDXVA_PictureParameters;
Members
wDecodedPictureIndex
Specifies the destination frame buffer for the decoded macroblocks.
wDeblockedPictureIndex
Specifies the destination frame buffer for the deblocked output picture when bPicDeblocked is 1. This member has no meaning and must be zero if bPicDeblocked is zero. This member may be the same as wDecodedPictureIndex.
wForwardRefPictureIndex
Specifies the frame buffer index of the picture to be used as a reference picture for forward prediction of the current picture. Must not be the same as wDecodedPictureIndex. This member must be 0xFFFF if bPicIntra is 1.
wBackwardRefPictureIndex
Specifies the frame buffer index of the picture to be used as a reference picture for backward prediction of the current picture. This member must not be the same as wDecodedPictureIndex if backward reference motion prediction is used. This member must be 0xFFFF if bPicBackwardPrediction is zero.
wPicWidthInMBminus1
Specifies the width of the current picture in units of macroblocks, minus 1. The width of the picture in macroblocks is derived by adding 1 to wPicWidthInMBminus1.
wPicHeightInMBminus1
Specifies the height of the current picture in units of macroblocks, minus 1. The height of the picture in macroblocks is derived by adding 1 to wPicHeightInMBminus1.
bMacroblockWidthMinus1
Specifies the destination luminance sample width of a macroblock, minus 1. This is equal to 15 for MPEG-1, MPEG-2, H.263, and MPEG-4.
bMacroblockHeightMinus1
Specifies the destination luminance sample height of a macroblock, minus 1. This is equal to 15 for MPEG-1, MPEG-2, H.261, H.263, and MPEG-4.
bBlockWidthMinus1
Specifies the block width of a residual difference block minus 1. This is equal to 7 for MPEG-1, MPEG-2, H.261, H.263, and MPEG-4. This is 7 if the bConfig4GroupedCoefs member of the DXVA_ConfigPictureDecode structure is 1. Residual difference blocks within a macroblock are sent in the order specified as in MPEG-2 Figures 6-10, 6-11, and 6-12 (raster-scan order for Y, followed by all 4:2:0 blocks of Cb in raster-scan order, followed by 4:2:0 blocks of Cr, followed by 4:2:2 blocks of Cb, followed by 4:2:2 blocks of Cr, followed by 4:4:4 blocks of Cb, followed by 4:4:4 blocks of Cr). A derived term called WT is formed by adding 1 to bBlockWidthMinus1.
bBlockHeightMinus1
Specifies the block height of a residual difference block, minus 1. This is equal to 7 for MPEG-1, MPEG-2, H.261, H.263, and MPEG-4. This is 7 if bConfig4GroupedCoefs is 1. A derived term called HT is formed by adding 1 to bBlockHeightMinus1.
bBPPminus1
Specifies the number of bits per pixel for the video sample values, minus 1. This is at least 7 (indicating 8-bit pixels). This is equal to 7 for MPEG-1, MPEG-2, H.261, and H.263. A larger number of bits per pixel is supported in some operational modes of MPEG-4. A derived term called BPP is formed by adding 1 to bBPPminus1.
bPicStructure
Indicates whether the current picture is a top-field picture (a value 1), a bottom-field picture (a value 2), or a frame picture (a value 3). In progressive-scan frame-structured coding such as in H.261, bPicStructure is 3. A derived value PicCurrentField is defined as zero unless bPicStructure is 2 (bottom field). In which case, it is 1. This member has the same meaning as the picture_structure variable defined in Section 6.3.10 and Table 6-14 of MPEG-2 (H.262).
bSecondField
Indicates whether, in the case of field-structured coding (when bPicStructure is 1 or 2), the current field is the second field of a picture. This is used to determine whether the opposite-parity field used as a reference for the opposite-parity lines for motion compensation prediction is the opposite-parity field of the reference picture or the opposite-parity field of the current picture. If bSecondField is 1, the current field is the second field of a picture and the field used as a reference for the opposite-parity lines for motion compensation are the opposite-parity lines of the current picture. (In both cases, the field used as a reference for the same-parity lines for motion compensation are the same-parity lines of the reference picture.) Otherwise, bSecondField is zero.
bPicIntra
Indicates whether motion-compensated prediction is needed for this picture. If bPicIntra is 1, all macroblocks are sent with either the DXVA_MBctrl_I_OffHostIDCT_1 or DXVA_MBctrl_I_HostResidDiff_1 macroblock control command structure, in which the IntraMacroblock flag is equal to 1 . That is, no motion-compensated prediction is performed for the picture. Otherwise, some macroblocks of the picture may have the IntraMacroblock parameter of the macroblock control command equal to zero, and the macroblock control command structure will use the DXVA_MBctrl_P_HostResidDiff_1 structure or the DXVA_MBctrl_P_OffHostIDCT_1 structure.
bPicBackwardPrediction
Indicates whether any macroblocks of the current picture might include backward prediction. If bPicIntra is 1, bPicBackwardPrediction must be zero. If bPicBackwardPrediction is zero, MotionBackward must be zero in all macroblock control commands of the picture (within each DXVA_MBctrl_I_HostResidDiff_1, DXVA_MBctrl_I_OffHostIDCT_1, DXVA_MBctrl_P_HostResidDiff_1, or DXVA_MBctrl_P_OffHostIDCT_1 structure). If bPicBackwardPrediction is 1, some macroblocks of the picture may have MotionBackward equal to 1.
bBidirectionalAveragingMode
Indicates the rounding method for combining prediction planes in bidirectional motion compensation (used for B pictures and dual-prime motion). The value zero indicates MPEG-1 and MPEG-2 rounded averaging (in which values halfway between two integers are rounded upward to the next higher integer), and the value 1 indicates H.263 truncated averaging (in which values halfway between two integers are rounded downward to the next lower integer). bBidirectionalAveragingMode must be zero if no bidirectional averaging is needed.
bMVprecisionAndChromaRelation
This member indicates the precision of luminance motion vectors and how chrominance motion vectors are derived from luminance motion vectors.
The following table lists values for this member with the specified luminance motion vector precision and a description of how the chrominance motion vectors are derived.
| Value | Description |
|---|---|
| 0 | Luminance motion vectors have half-sample precision. Chrominance motion vectors are derived from luminance motion vectors in accordance with MPEG-2 (H.262) . |
| 1 | Luminance motion vectors have half-sample precision. Chrominance motion vectors are derived from luminance motion vectors in accordance with H.263 . |
| 2 | Luminance motion vectors have full-sample precision. Chrominance motion vectors are derived from luminance motion vectors in accordance with H.261 (dividing by two and truncating toward zero to full-sample values). |
| 3 | Reserved. |
bChromaFormat
Affects the number of prediction error blocks expected by the accelerator. This variable is defined in MPEG-2 (H.262). For MPEG-1, MPEG-2 Main Profile, H.261 and H.263 bitstreams, this value must always be set to 1, indicating 4:2:0 format. If a value of 2, this indicates 4:2:2, and if a value of 3, indicates 4:4:4 sampling. This member must be equal to 1 if the bConfig4GroupedCoefs member of DXVA_ConfigPictureDecode is 1 (because bConfig4GroupedCoefs operation does not include the EOB indication needed within coefficient data in 4:2:2 and 4:4:4 formats).
Note
Horizontal chroma siting differs slightly among H.261, H.263, and MPEG-1 versus MPEG-2 and MPEG-4. This difference is assumed to be small enough to ignore.
bPicScanFixed
When using accelerator-based IDCT processing of residual difference blocks, a value of 1 for this flag indicates that the inverse-scan method is the same for all macroblocks in the picture. A value of zero indicates that it is not. This member must be 1 if the bConfigHostInverseScan member is 1 or if the bConfigResidDiffAccelerator member is zero in DXVA_ConfigPictureDecode.
bPicScanMethod
Indicates the fixed inverse scan method for the picture when bPicScanFixed is 1. When bPicScanFixed is zero, this member has no meaning and must have a value of zero.
If the bConfigHostInverseScan member of DXVA_ConfigPictureDecode is zero, the scan method defined by this member can be one of the following.
| bPicScanMethod | Scan Method |
|---|---|
| 0 | Zigzag scan (MPEG-2) |
| 1 | Alternate-vertical scan (MPEG-2) |
| 2 | Alternate-horizontal scan (H.263) |
If the bConfigHostInverseScan member of DXVA_ConfigPictureDecode is 1, the scan method defined by bPicScanMethod must be set as follows.
| bPicScanMethod | Scan Method |
|---|---|
| 3 | Arbitrary scan with absolute coefficient address. |
bPicReadbackRequests
Indicates whether read-back control requests are issued for the current picture. A value of 1 indicates that read-back requests are present, and a value of zero indicates that they are not. Read-back requests indicate that values of macroblocks are read back in the final decoded and deblocked picture (if deblocking is applied with wDeblockedPictureIndex equal to wDecodedPictureIndex).
bRcontrol
Defines the rounding method to be used for half-sample motion compensation. This variable is defined in H.263 Section 6.1.2. A value of zero indicates the half-sample rounding method found in MPEG-1, MPEG-2, and the first version of H.263. A value of 1 indicates the rounding method that includes a downward averaging bias that can be selected in some optional modes of H.263 and MPEG-4. It is meaningless for H.261, because H.261 has no half-sample motion compensation. It must be set to zero for all MPEG-1 and MPEG-2 bitstreams in order to conform with the rounding operator defined by those standards.
bPicSpatialResid8
Indicates how spatial-domain difference blocks are sent to the accelerator from the host. A value of 1 indicates that spatial-domain difference blocks for host-based residual difference decoding can be sent using 8-bit samples, and a value of zero indicates that they cannot.
This member must be zero if the bConfigResidDiffHost member of DXVA_ConfigPictureDecode is zero or if BPP is greater than 8. This member must be 1 if BPP is 8, bPicIntra is 1 and bConfigResidDiffHost is 1. This member must be 1 if the bConfigSpatialResid8 member of DXVA_ConfigPictureDecode is 1.
If this member is equal to 1, spatial-domain intra macroblocks are sent as 8-bit values (that are either signed or unsigned, as determined by the bConfigIntraResidUnsigned member of DXVA_ConfigPictureDecode), and spatial-domain nonintra macroblock differences are sent as signed 8-bit difference values relative to some motion-compensated prediction.
The bPicSpatialResid8 member differs from the bConfigSpatialResid8 member of DXVA_ConfigPictureDecode in that it is an indication for a particular picture, not a global indication for the entire video sequence. In some cases such as in an intra picture with BPP equal to 8, bPicSpatialResid8 will be 1 even though bConfigSpatialResid8 may be zero.
bPicOverflowBlocks
Indicates whether spatial-domain difference blocks are sent to the accelerator from the host using overflow blocks. A value of 1 indicates that spatial-domain difference blocks for host-based residual difference decoding of a picture may be sent using overflow blocks. A value of zero indicates that spatial-domain difference blocks are not sent using overflow blocks. This member must be zero if bConfigResidDiffHost is zero or if bConfigSpatialResid8 is zero, or if BPP is greater than 8. Parameters bConfigResidDiffHost and bConfigSpatialResid8 are members of DXVA_ConfigPictureDecode. bPicOverflowBlocks indicates whether any overflow blocks may be present for the particular picture. In an intra picture with BPP equal to 8, bPicOverflowBlocks must be zero as no overflow blocks are needed in this case.
bPicExtrapolation
Indicates whether motion vectors over picture boundaries are allowed as specified by H.263 Annex D and MPEG-4. This requires either allocation of picture planes that are two macroblocks wider (one extra macroblock at the left and another at the right) and two macroblocks taller (one extra macroblock at the top and another at the bottom) than the decoded picture size, or clipping of the address of each individual pixel access to within the picture boundaries. Macroblock addresses in this specification are for macroblocks in the interior of the picture, not including padding.
bPicDeblocked
Indicates whether deblocking commands are sent for this picture to create a deblocked output picture. The deblocked output picture is placed in the picture buffer indicated by wDeblockedPictureIndex. If bPicDeblocked is 1, deblocking commands are sent and the deblocked frame is generated. If bPicDeblocked is zero, no deblocking commands are sent and no deblocked picture is generated.
bPicDeblockConfined
Indicates whether deblocking filter command buffers confine the effect of deblocking filter operations to the set of macroblocks contained in the deblocking filter command buffer.
bPic4MVallowed
Specifies whether four forward-reference motion vectors per macroblock are allowed as used in H.263 Annexes F and J.
bPicOBMC
Specifies whether motion compensation for the current picture operates using overlapped block motion compensation (OBMC) as specified in H.263 Annex F. Must be zero if bPic4MVallowed is zero.
bPicBinPB
Specifies whether bidirectionally predicted macroblocks in the picture use B-picture in PB-frame motion compensation. This restricts the bidirectionally predicted area for each macroblock to the region of the corresponding macroblock in the backward reference picture, as specified in Annexes G and M of H.263.
bMV_RPS
Specifies the use of motion vector reference picture selection. If bMV_RPS is 1, this indicates that a reference picture index is sent for each motion vector rather than just forward and possibly backward motion picture indexes for the picture as a whole. If bMV_RPS is 1, the wForwardRefPictureIndex and wBackwardRefPictureIndex members have no meaning and must be zero.
bReservedBits
This is reserved for packing and alignment. Must be zero.
wBitstreamFcodes
Indicates the motion vector f_code values as defined in MPEG-2 for raw bitstream processing. Each f_code value takes 4 bits. These values are packed into a 16-bit word as follows.
| Bits | Description |
|---|---|
| 12 through 15 (the most significant bits) | f_code[0][0]: The forward horizontal f_code |
| 8 through 11 | f_code[0][1]: The forward vertical f_code |
| 4 through 7 | f_code[1][0]: The backward horizontal f_code |
| 0 through 3 (the least significant bits) | f_code[1][1]: The backward vertical f_code |
When the bConfigBitstreamRaw member of the DXVA_ConfigPictureDecode structure is 1, wBitstreamFcodes contains four motion vector f_code values. If bConfigBitstreamRaw is 1 and any of the four f_code values is unnecessary or irrelevant due to the structure of the bitstream data or due to the f_code value not being needed in the relevant video coding bitstream syntax (such as in H.261 or H.263), then each irrelevant f_code value is 0xF.
If the bConfigBitstreamRaw member of the DXVA_ConfigPictureDecode structure is zero, then wBitstreamFcodes is set to 0xFFFF (all f_code values are set to 0xF).
Note
MPEG-1 bitstreams provide this information in a different form. Therefore for MPEG-1 bitstreams, f_code[0][0] and f_code[0][1] are equal to MPEG-1's forward_f_code, and f_code[1][0] and f_code[1][1] are equal to MPEG-1's backward_f_code.
wBitstreamPCEelements
When the bConfigBitstreamRaw member of DXVA_ConfigPictureDecode is 1, this member contains a set of flags necessary for the bitstream decoding process of MPEG-2 video. It is not used and must be zero when bConfigBitstreamRaw is zero and for non-MPEG-2 video. The bits in this member are defined by their correspondence with bitstream elements of the MPEG-2 picture coding extension as follows.
| Bits | Description |
|---|---|
| 14 and 15 | IntraDCprecision is equal to intra_dc_precision. |
| 12 and 13 | AnotherPicStructure is equal to picture_structure. This must be equal to the bPicStructure member of this structure. |
| 11 | TopFieldFirst is equal to top_field_first. |
| 10 | FrameDCTprediction is equal to frame_pred_frame_dct. |
| 9 | ConcealmentMVs is equal to concealment_motion_vectors. |
| 8 | QuantScaleType is equal to q_scale_type. |
| 7 | IntraVLCformat is equal to intra_vlc_format. |
| 6 | AlternateScan is equal to alternate_scan. |
| 5 | RepeatFirstField is equal to repeat_first_field (not needed by the accelerator). |
| 4 | Chroma420type is equal to chroma_420_type (not needed by the accelerator and restricted by MPEG-2 to be equal to progressive_frame). |
| 3 | ProgressiveFrame is equal to progressive_frame. |
| 0, 1, and 2 | Reserved Bits. These are the least significant bits. |
bBitstreamConcealmentNeed
Indicates the likelihood of errors in the bitstream data when the bConfigBitstreamRaw member of the DXVA_ConfigPictureDecode structure is 1. Must be zero if bConfigBitstreamRaw is zero.
Video accelerators must be designed not to fail or lock up, regardless of the content of the data given to them. Therefore, it may be helpful for a video accelerator to have information about the host's assessment of the likelihood of syntactical errors. This is in order to determine whether there is a need to invoke a more complex error concealment algorithm that might slow down the bitstream decoding process. Allowed values for this member are as follows (all other values are reserved).
| Value | Meaning |
|---|---|
| 0 | The bitstream is unlikely to contain any significant amount of errors in its syntactical format. |
| 1 | The bitstream may contain some errors. These errors are likely to be infrequent (for example, an error once or twice per hour). |
| 2 | The bitstream is likely to contain some errors. These errors are likely to occur with a frequency that could impact the user experience (for example, an error every five to ten minutes). |
| 3 | The bitstream is likely to contain relatively significant, serious, and frequent syntactical format errors (for example, one or more errors per minute). |
bBitstreamConcealmentMethod
Specifies a preferred default method for error concealment processing when the bConfigBitstreamRaw member of the DXVA_ConfigPictureDecode structure is 1. Must be zero if bConfigBitstreamRaw is zero. Allowed values for this member are as follows (all other values are reserved).
| Value | Error Concealment Method |
|---|---|
| 0 | Unknown or unspecified. |
| 1 | Spatial intra-picture concealment within the picture. |
| 2 | Forward-motion reference picture for inter-picture concealment (to be used more typically in a P picture or in a B picture that is closer to its forward-motion reference picture than to its backward-motion reference picture). |
| 3 | Backward-motion reference picture for inter-picture concealment (to be used more typically in a B picture that is closer to its backward-motion reference picture than to its forward-motion reference picture). |
Remarks
Certain members of this structure are constrained to specific values by the configuration established using the DXVA_ConfigPictureDecode structure. After the picture-level parameters are conveyed using DXVA_PictureParameters, the picture decoding process is primarily governed by macroblock control commands formed using the DXVA_MBctrl_I_HostResidDiff_1, DXVA_MBctrl_I_OffHostIDCT_1, DXVA_MBctrl_P_HostResidDiff_1, or DXVA_MBctrl_P_OffHostIDCT_1 structures.
Requirements
| Requirement | Value |
|---|---|
| Header | dxva.h (include Dxva.h) |
See also
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