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Structures

VkSamplerYcbcrConversionImageFormatProperties

Structure specifying combined image sampler descriptor count for multi-planar images

To determine the number of descriptors required to support an image format for sampled images with Y′CBCR conversion, add VkSamplerYcbcrConversionImageFormatProperties to the pNext chain of the VkImageFormatProperties2 structure in a call to vkGetPhysicalDeviceImageFormatProperties2.

The VkSamplerYcbcrConversionImageFormatProperties structure is defined as:

typedef struct VkSamplerYcbcrConversionImageFormatProperties {
    VkStructureType sType;
    void* pNext;
    uint32_t combinedImageSamplerDescriptorCount;
} VkSamplerYcbcrConversionImageFormatProperties;

typedef VkSamplerYcbcrConversionImageFormatProperties VkSamplerYcbcrConversionImageFormatPropertiesKHR;
  • sType is a VkStructureType value identifying this structure.
  • pNext is NULL or a pointer to a structure extending this structure.
  • combinedImageSamplerDescriptorCount is the number of descriptors that the implementation uses to access a sampled image with Y′CBCR conversion

combinedImageSamplerDescriptorCount is a number between 1 and the number of planes in the format.

The size an image descriptor with a VkSamplerYcbcrConversionInfo structure consumes in the resource heap is multiplied by the combinedImageSamplerDescriptorCount of its format. These images are sampled with embedded samplers and therefore do not consume space in the sampler heap.

For descriptor buffers or descriptor sets, each combined image sampler descriptor binding with a layout that includes at least one immutable Y′CBCR conversion sampler will internally use a number of descriptors equal to the maximum combinedImageSamplerDescriptorCount of the formats of all the immutable Y′CBCR conversion samplers in that binding.

This expanded number of descriptors will be consumed from the descriptor pool when a descriptor set is allocated, and counts towards the maxDescriptorSetSamplers, maxDescriptorSetSampledImages, maxPerStageDescriptorSamplers, and maxPerStageDescriptorSampledImages limits.

All descriptors in a binding use the same expanded number of descriptors to allow implementations to use a uniform stride for dynamic indexing.For example, consider a descriptor set layout binding with two immutable Y′CBCR samplers with formats that have VkSamplerYcbcrConversionImageFormatProperties::combinedImageSamplerDescriptorCount values of 2 and 3 respectively. The maximum combinedImageSamplerDescriptorCount for this binding layout is therefore 3.If there are 3 descriptors in a descriptor set binding with this layout, including one descriptor without an immutable Y′CBCR sampler, the binding will consume 9 combined image sampler descriptors from the descriptor pool.For descriptor heaps, the application explicitly maps the descriptor binding to a heap offset with VkDescriptorSetAndBindingMappingEXT and should make similar calculations as it must offset each element in the binding correctly.

Instead of querying all the potential formats that an application might use, it can use VkPhysicalDeviceMaintenance6Properties::maxCombinedImageSamplerDescriptorCount property to determine the maximum combinedImageSamplerDescriptorCount for all formats the implementation supports.

Valid Usage (Implicit)

VUID-VkSamplerYcbcrConversionImageFormatProperties-sType-sType

sType must be VK_STRUCTURE_TYPE_SAMPLER_YCBCR_CONVERSION_IMAGE_FORMAT_PROPERTIES