# VkVideoEncodeH264CapabilitiesKHR(3) Manual Page

## Name

VkVideoEncodeH264CapabilitiesKHR - Structure describing H.264 encode capabilities

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## C Specification

When calling vkGetPhysicalDeviceVideoCapabilitiesKHR to query the capabilities for an H.264 encode profile, the VkVideoCapabilitiesKHR::`pNext` chain must include a `VkVideoEncodeH264CapabilitiesKHR` structure that will be filled with the profile-specific capabilities.

The `VkVideoEncodeH264CapabilitiesKHR` structure is defined as:

    // Provided by VK_KHR_video_encode_h264
    typedef struct VkVideoEncodeH264CapabilitiesKHR {
        VkStructureType                        sType;
        void*                                  pNext;
        VkVideoEncodeH264CapabilityFlagsKHR    flags;
        StdVideoH264LevelIdc                   maxLevelIdc;
        uint32_t                               maxSliceCount;
        uint32_t                               maxPPictureL0ReferenceCount;
        uint32_t                               maxBPictureL0ReferenceCount;
        uint32_t                               maxL1ReferenceCount;
        uint32_t                               maxTemporalLayerCount;
        VkBool32                               expectDyadicTemporalLayerPattern;
        int32_t                                minQp;
        int32_t                                maxQp;
        VkBool32                               prefersGopRemainingFrames;
        VkBool32                               requiresGopRemainingFrames;
        VkVideoEncodeH264StdFlagsKHR           stdSyntaxFlags;
    } VkVideoEncodeH264CapabilitiesKHR;

## Members

- `sType` is a VkStructureType value identifying this structure.

- `pNext` is `NULL` or a pointer to a structure extending this structure.

- `flags` is a bitmask of VkVideoEncodeH264CapabilityFlagBitsKHR indicating supported H.264 encoding capabilities.

- `maxLevelIdc` is a `StdVideoH264LevelIdc` value indicating the maximum H.264 level supported by the profile, where enum constant `STD_VIDEO_H264_LEVEL_IDC_<major>_<minor>` identifies H.264 level `<major>.<minor>` as defined in section A.3 of the ITU-T H.264 Specification.

- `maxSliceCount` indicates the maximum number of slices that can be encoded for a single picture. Further restrictions may apply to the number of slices that can be encoded for a single picture depending on other capabilities and codec-specific rules.

- `maxPPictureL0ReferenceCount` indicates the maximum number of reference pictures the implementation supports in the reference list L0 for P pictures.

  Note | As implementations may override the reference lists, `maxPPictureL0ReferenceCount` does not limit the number of elements that the application can specify in the L0 reference list for P pictures. However, if `maxPPictureL0ReferenceCount` is zero, then the use of P pictures is not allowed.

- `maxBPictureL0ReferenceCount` indicates the maximum number of reference pictures the implementation supports in the reference list L0 for B pictures.

- `maxL1ReferenceCount` indicates the maximum number of reference pictures the implementation supports in the reference list L1 if encoding of B pictures is supported.

  Note | As implementations may override the reference lists, `maxBPictureL0ReferenceCount` and `maxL1ReferenceCount` does not limit the number of elements that the application can specify in the L0 and L1 reference lists for B pictures. However, if `maxBPictureL0ReferenceCount` and `maxL1ReferenceCount` are both zero, then the use of B pictures is not allowed.

- `maxTemporalLayerCount` indicates the maximum number of H.264 temporal layers supported by the implementation.

- `expectDyadicTemporalLayerPattern` indicates that the implementation’s rate control algorithms expect the application to use a dyadic temporal layer pattern when encoding multiple temporal layers.

- `minQp` indicates the minimum QP value supported.

- `maxQp` indicates the maximum QP value supported.

- `prefersGopRemainingFrames` indicates that the implementation’s rate control algorithm prefers the application to specify the number of frames of each type remaining in the current group of pictures when beginning a video coding scope.

- `requiresGopRemainingFrames` indicates that the implementation’s rate control algorithm requires the application to specify the number of frames of each type remaining in the current group of pictures when beginning a video coding scope.

- `stdSyntaxFlags` is a bitmask of VkVideoEncodeH264StdFlagBitsKHR indicating capabilities related to H.264 syntax elements.

## Description

Valid Usage (Implicit)

- VUID-VkVideoEncodeH264CapabilitiesKHR-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_VIDEO_ENCODE_H264_CAPABILITIES_KHR`

## See Also

VK_KHR_video_encode_h264, VkBool32, VkStructureType, VkVideoEncodeH264CapabilityFlagsKHR, VkVideoEncodeH264StdFlagsKHR

## Document Notes

For more information, see the Vulkan Specification

This page is extracted from the Vulkan Specification. Fixes and changes should be made to the Specification, not directly.

## Copyright

Copyright 2014-2025 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0