vkCmdEncodeVideoKHR

To launch video encode operations, call:

void vkCmdEncodeVideoKHR(
    VkCommandBuffer commandBuffer,
    const VkVideoEncodeInfoKHR* pEncodeInfo);

• commandBuffer is the command buffer in which to record the command.
• pEncodeInfo is a pointer to a VkVideoEncodeInfoKHR structure specifying the parameters of the video encode operations.

Each call issues one or more video encode operations. The implicit parameter opCount corresponds to the number of video encode operations issued by the command. After calling this command, the active query index of each active query is incremented by opCount.

Currently each call to this command results in the issue of a single video encode operation.

If the bound video session was created with VK_VIDEO_SESSION_CREATE_INLINE_QUERIES_BIT_KHR and the pNext chain of pEncodeInfo includes a VkVideoInlineQueryInfoKHR structure with its queryPool member specifying a valid VkQueryPool handle, then this command will execute a query for each video encode operation issued by it.

Active Reference Picture Information

The list of active reference pictures used by a video encode operation is a list of image subregions used as the source of reference picture data and related parameters, and is derived from the VkVideoReferenceSlotInfoKHR structures provided as the elements of the pEncodeInfo→pReferenceSlots array. For each element of pEncodeInfo→pReferenceSlots, one or more elements are added to the active reference picture list, as defined by the codec-specific semantics. Each element of this list contains the following information:

• The image subregion within the image subresource referred to by the video picture resource used as the reference picture.
• The DPB slot index the reference picture is associated with.
• The codec-specific reference information related to the reference picture.

Reconstructed Picture Information

Information related to the optional reconstructed picture used by a video encode operation is derived from the VkVideoReferenceSlotInfoKHR structure pointed to by pEncodeInfo→pSetupReferenceSlot, if not NULL, as defined by the codec-specific semantics, and consists of the following:

• The image subregion within the image subresource referred to by the video picture resource used as the reconstructed picture.
• The DPB slot index to use for picture reconstruction.
• The codec-specific reference information related to the reconstructed picture.

Specifying a valid VkVideoReferenceSlotInfoKHR structure in pEncodeInfo→pSetupReferenceSlot is always required, unless the video session was created with VkVideoSessionCreateInfoKHR::maxDpbSlot equal to zero. However, the DPB slot identified by pEncodeInfo→pSetupReferenceSlot→slotIndex is only activated with the reconstructed picture specified in pEncodeInfo→pSetupReferenceSlot→pPictureResource if reference picture setup is requested according to the codec-specific semantics.

If reconstructed picture information is specified, but reference picture setup is not requested, according to the codec-specific semantics, the contents of the video picture resource corresponding to the reconstructed picture will be undefined: after the video encode operation.

Encode Input Picture Information

Information related to the encode input picture used by a video encode operation is derived from pEncodeInfo→srcPictureResource and any codec-specific parameters provided in the pEncodeInfo→pNext chain, as defined by the codec-specific semantics, and consists of the following:

• The image subregion within the image subresource referred to by the video picture resource used as the encode input picture.
• The codec-specific picture information related to the encoded picture.

Several limiting values are defined below that are referenced by the relevant valid usage statements of this command.

• Let uint32_t activeReferencePictureCount be the size of the list of active reference pictures used by the video encode operation. Unless otherwise defined, activeReferencePictureCount is set to the value of pEncodeInfo→referenceSlotCount.
• Let VkOffset2D codedOffsetGranularity be the minimum alignment requirement for the coded offset of video picture resources. Unless otherwise defined, the value of the x and y members of codedOffsetGranularity are 0.
• Let uint32_t dpbFrameUseCount[] be an array of size maxDpbSlots, where maxDpbSlots is the VkVideoSessionCreateInfoKHR::maxDpbSlots the bound video session was created with, with each element indicating the number of times a frame associated with the corresponding DPB slot index is referred to by the video coding operation. Let the initial value of each element of the array be 0.
  • If pEncodeInfo→pSetupReferenceSlot is not NULL, then dpbFrameUseCount[i] is incremented by one, where i equals pEncodeInfo→pSetupReferenceSlot→slotIndex.
  • For each element of pEncodeInfo→pReferenceSlots, dpbFrameUseCount[i] is incremented by one, where i equals the slotIndex member of the corresponding element.
• Let VkExtent2D maxCodingBlockSize be the maximum codec-specific coding block size that may be used by the video encode operation.
  • If the bound video session object was created with an H.264 encode profile, then let maxCodingBlockSize be equal to the size of an H.264 macroblock, i.e. {16,16}.
  • If the bound video session object was created with an H.265 encode profile, then let maxCodingBlockSize be equal to the maximum H.265 coding block size that may be used by the video encode operation derived as the maximum of the CTB sizes corresponding to the VkVideoEncodeH265CtbSizeFlagBitsKHR bits set in VkVideoEncodeH265CapabilitiesKHR::ctbSizes, as returned by vkGetPhysicalDeviceVideoCapabilitiesKHR for the video profile the bound video session was created with.
  • Otherwise, maxCodingBlockSize is undefined:.
• If maxCodingBlockSize is defined, then let VkExtent2D minCodingBlockExtent be the coded extent of the encode input picture expressed in terms of codec-specific coding blocks, assuming the maximum size of such coding blocks, as defined by maxCodingBlockSize, calculated from the value of the codedExtent member of pEncodeInfo→srcPictureResource as follows:
  • minCodingBlockExtent.width = (codedExtent.width\
    maxCodingBlockSize.width - 1) / maxCodingBlockSize.width
  • minCodingBlockExtent.height = (codedExtent.height\
    maxCodingBlockSize.height - 1) / maxCodingBlockSize.height
• If the bound video session object was created with an H.264 encode profile, then:
  • Let StdVideoH264PictureType h264PictureType be the picture type of the encoded picture set to the value of pStdPictureInfo→primary_pic_type specified in the VkVideoEncodeH264PictureInfoKHR structure included in the pEncodeInfo→pNext chain.
  • Let StdVideoH264PictureType h264L0PictureTypes[] and StdVideoH264PictureType h264L1PictureTypes[] be the picture types of the reference pictures in the L0 and L1 reference lists, respectively. If pStdPictureInfo→pRefLists specified in the VkVideoEncodeH264PictureInfoKHR structure included in the pEncodeInfo→pNext chain is not NULL, then for each reference index specified in the elements of the pStdPictureInfo→pRefLists→RefPicList0 and pStdPictureInfo→pRefLists→RefPicList1 arrays, if the reference index is not STD_VIDEO_H264_NO_REFERENCE_PICTURE, pStdReferenceInfo→primary_pic_type is added to h264L0PictureTypes or h264L1PictureTypes, respectively, where pStdReferenceInfo is the member of the VkVideoEncodeH264DpbSlotInfoKHR structure included in the pNext chain of the element of pEncodeInfo→pReferenceSlots for which slotIndex equals the reference index in question.
• If the bound video session object was created with an H.265 encode profile, then:
  • Let StdVideoH265PictureType h265PictureType be the picture type of the encoded picture set to the value of pStdPictureInfo→pic_type specified in the VkVideoEncodeH265PictureInfoKHR structure included in the pEncodeInfo→pNext chain.
  • Let StdVideoH265PictureType h265L0PictureTypes[] and StdVideoH265PictureType h265L1PictureTypes[] be the picture types of the reference pictures in the L0 and L1 reference lists, respectively. If pStdPictureInfo→pRefLists specified in the VkVideoEncodeH265PictureInfoKHR structure included in the pEncodeInfo→pNext chain is not NULL, then for each reference index specified in the elements of the pStdPictureInfo→pRefLists→RefPicList0 and pStdPictureInfo→pRefLists→RefPicList1 arrays, if the reference index is not STD_VIDEO_H265_NO_REFERENCE_PICTURE, pStdReferenceInfo→pic_type is added to h265L0PictureTypes or h265L1PictureTypes, respectively, where pStdReferenceInfo is the member of the VkVideoEncodeH265DpbSlotInfoKHR structure included in the pNext chain of the element of pEncodeInfo→pReferenceSlots for which slotIndex equals the reference index in question.