VkVideoEncodeH264PictureInfoKHR

The VkVideoEncodeH264PictureInfoKHR structure is defined as:

typedef struct VkVideoEncodeH264PictureInfoKHR {
    VkStructureType sType;
    const void* pNext;
    uint32_t naluSliceEntryCount;
    const VkVideoEncodeH264NaluSliceInfoKHR* pNaluSliceEntries;
    const StdVideoEncodeH264PictureInfo* pStdPictureInfo;
    VkBool32 generatePrefixNalu;
} VkVideoEncodeH264PictureInfoKHR;

• sType is a VkStructureType value identifying this structure.
• pNext is NULL or a pointer to a structure extending this structure.
• naluSliceEntryCount is the number of elements in pNaluSliceEntries.
• pNaluSliceEntries is a pointer to an array of naluSliceEntryCount VkVideoEncodeH264NaluSliceInfoKHR structures specifying the parameters of the individual H.264 slices to encode for the input picture.
• pStdPictureInfo is a pointer to a StdVideoEncodeH264PictureInfo structure specifying H.264 picture information.
• generatePrefixNalu controls whether prefix NALUs are generated before slice NALUs into the target bitstream, as defined in sections 7.3.2.12 and 7.4.2.12 of the ITU-T H.264 Specification.

This structure is specified in the pNext chain of the VkVideoEncodeInfoKHR structure passed to vkCmdEncodeVideoKHR to specify the codec-specific picture information for an H.264 encode operation.

Encode Input Picture Information

When this structure is specified in the pNext chain of the VkVideoEncodeInfoKHR structure passed to vkCmdEncodeVideoKHR, the information related to the encode input picture is defined as follows:

• The image subregion used is determined according to the H.264 Encode Picture Data Access section.
• The encode input picture is associated with the H.264 picture information provided in pStdPictureInfo.

Std Picture Information

The members of the StdVideoEncodeH264PictureInfo structure pointed to by pStdPictureInfo are interpreted as follows:

• flags.reserved and reserved1 are used only for padding purposes and are otherwise ignored;
• flags.IdrPicFlag as defined in section 7.4.1 of the ITU-T H.264 Specification;
• flags.is_reference as defined in section 3.136 of the ITU-T H.264 Specification;
• seq_parameter_set_id and pic_parameter_set_id are used to identify the active parameter sets, as described below;
• primary_pic_type as defined in section 7.4.2 of the ITU-T H.264 Specification;
• PicOrderCnt as defined in section 8.2 of the ITU-T H.264 Specification;
• temporal_id as defined in section G.7.4.1.1 of the ITU-T H.264 Specification;
• if pRefLists is not NULL, then it is a pointer to a StdVideoEncodeH264ReferenceListsInfo structure that is interpreted as follows:
  • flags.reserved is used only for padding purposes and is otherwise ignored;
  • ref_pic_list_modification_flag_l0 and ref_pic_list_modification_flag_l1 as defined in section 7.4.3.1 of the ITU-T H.264 Specification;
  • num_ref_idx_l0_active_minus1 and num_ref_idx_l1_active_minus1 as defined in section 7.4.3 of the ITU-T H.264 Specification;
  • RefPicList0 and RefPicList1 as defined in section 8.2.4 of the ITU-T H.264 Specification where each element of these arrays either identifies an active reference picture using its DPB slot index or contains the value STD_VIDEO_H264_NO_REFERENCE_PICTURE to indicate no reference picture;
  • if refList0ModOpCount is not zero, then pRefList0ModOperations is a pointer to an array of refList0ModOpCount number of StdVideoEncodeH264RefListModEntry structures specifying the modification parameters for the reference list L0 as defined in section 7.4.3.1 of the ITU-T H.264 Specification;
  • if refList1ModOpCount is not zero, then pRefList1ModOperations is a pointer to an array of refList1ModOpCount number of StdVideoEncodeH264RefListModEntry structures specifying the modification parameters for the reference list L1 as defined in section 7.4.3.1 of the ITU-T H.264 Specification;
  • if refPicMarkingOpCount is not zero, then refPicMarkingOperations is a pointer to an array of refPicMarkingOpCount number of StdVideoEncodeH264RefPicMarkingEntry structures specifying the reference picture marking parameters as defined in section 7.4.3.3 of the ITU-T H.264 Specification;
• all other members are interpreted as defined in section 7.4.3 of the ITU-T H.264 Specification.

Reference picture setup is controlled by the value of StdVideoEncodeH264PictureInfo::flags.is_reference. If it is set and a reconstructed picture is specified, then the latter is used as the target of picture reconstruction to activate the DPB slot specified in pEncodeInfo→pSetupReferenceSlot→slotIndex. If StdVideoEncodeH264PictureInfo::flags.is_reference is not set, but a reconstructed picture is specified, then the corresponding picture reference associated with the DPB slot is invalidated, as described in the DPB Slot States section.

Active Parameter Sets

The members of the StdVideoEncodeH264PictureInfo structure pointed to by pStdPictureInfo are used to select the active parameter sets to use from the bound video session parameters object, as follows:

• The active SPS is the SPS identified by the key specified in StdVideoEncodeH264PictureInfo::seq_parameter_set_id.
• The active PPS is the PPS identified by the key specified by the pair constructed from StdVideoEncodeH264PictureInfo::seq_parameter_set_id and StdVideoEncodeH264PictureInfo::pic_parameter_set_id.

H.264 encoding uses explicit weighted sample prediction for a slice, as defined in section 8.4.2.3 of the ITU-T H.264 Specification, if any of the following conditions are true for the active PPS and the pStdSliceHeader member of the corresponding element of pNaluSliceEntries:

• pStdSliceHeader→slice_type is STD_VIDEO_H264_SLICE_TYPE_P and weighted_pred_flag is enabled in the active PPS.
• pStdSliceHeader→slice_type is STD_VIDEO_H264_SLICE_TYPE_B and weighted_bipred_idc in the active PPS equals STD_VIDEO_H264_WEIGHTED_BIPRED_IDC_EXPLICIT.