# VkVideoEncodeH264CapabilityFlagBitsKHR(3) Manual Page

## Name

VkVideoEncodeH264CapabilityFlagBitsKHR - H.264 encode capability flags

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## C Specification

Bits which may be set in VkVideoEncodeH264CapabilitiesKHR::`flags`, indicating the H.264 encoding capabilities supported, are:

    // Provided by VK_KHR_video_encode_h264
    typedef enum VkVideoEncodeH264CapabilityFlagBitsKHR {
        VK_VIDEO_ENCODE_H264_CAPABILITY_HRD_COMPLIANCE_BIT_KHR = 0x00000001,
        VK_VIDEO_ENCODE_H264_CAPABILITY_PREDICTION_WEIGHT_TABLE_GENERATED_BIT_KHR = 0x00000002,
        VK_VIDEO_ENCODE_H264_CAPABILITY_ROW_UNALIGNED_SLICE_BIT_KHR = 0x00000004,
        VK_VIDEO_ENCODE_H264_CAPABILITY_DIFFERENT_SLICE_TYPE_BIT_KHR = 0x00000008,
        VK_VIDEO_ENCODE_H264_CAPABILITY_B_FRAME_IN_L0_LIST_BIT_KHR = 0x00000010,
        VK_VIDEO_ENCODE_H264_CAPABILITY_B_FRAME_IN_L1_LIST_BIT_KHR = 0x00000020,
        VK_VIDEO_ENCODE_H264_CAPABILITY_PER_PICTURE_TYPE_MIN_MAX_QP_BIT_KHR = 0x00000040,
        VK_VIDEO_ENCODE_H264_CAPABILITY_PER_SLICE_CONSTANT_QP_BIT_KHR = 0x00000080,
        VK_VIDEO_ENCODE_H264_CAPABILITY_GENERATE_PREFIX_NALU_BIT_KHR = 0x00000100,
      // Provided by VK_KHR_video_encode_h264 with VK_KHR_video_encode_quantization_map
        VK_VIDEO_ENCODE_H264_CAPABILITY_MB_QP_DIFF_WRAPAROUND_BIT_KHR = 0x00000200,
    } VkVideoEncodeH264CapabilityFlagBitsKHR;

## Description

- `VK_VIDEO_ENCODE_H264_CAPABILITY_HRD_COMPLIANCE_BIT_KHR` specifies whether the implementation may be able to generate HRD compliant bitstreams if any of the `nal_hrd_parameters_present_flag` or `vcl_hrd_parameters_present_flag` members of `StdVideoH264SpsVuiFlags` are set to `1` in the active SPS.

- `VK_VIDEO_ENCODE_H264_CAPABILITY_PREDICTION_WEIGHT_TABLE_GENERATED_BIT_KHR` specifies that if `StdVideoH264PpsFlags`::`weighted_pred_flag` is set to `1` or `StdVideoH264PictureParameterSet`::`weighted_bipred_idc` is set to `STD_VIDEO_H264_WEIGHTED_BIPRED_IDC_EXPLICIT` in the active PPS when encoding a P picture or B picture, respectively, then the implementation is able to internally decide syntax for `pred_weight_table`, as defined in section 7.4.3.2 of the ITU-T H.264 Specification, and the application is not required to provide a weight table in the H.264 slice header parameters.

- `VK_VIDEO_ENCODE_H264_CAPABILITY_ROW_UNALIGNED_SLICE_BIT_KHR` specifies that each slice in a frame with multiple slices may begin or finish at any offset in a macroblock row. If not supported, all slices in the frame must begin at the start of a macroblock row (and hence each slice must finish at the end of a macroblock row).

- `VK_VIDEO_ENCODE_H264_CAPABILITY_DIFFERENT_SLICE_TYPE_BIT_KHR` specifies that when a frame is encoded with multiple slices, the implementation allows encoding each slice with a different `StdVideoEncodeH264SliceHeader`::`slice_type` specified in the H.264 slice header parameters. If not supported, all slices of the frame must be encoded with the same `slice_type` which corresponds to the picture type of the frame.

- `VK_VIDEO_ENCODE_H264_CAPABILITY_B_FRAME_IN_L0_LIST_BIT_KHR` specifies support for using a B frame as L0 reference, as specified in `StdVideoEncodeH264ReferenceListsInfo`::`RefPicList0` in the H.264 picture information.

- `VK_VIDEO_ENCODE_H264_CAPABILITY_B_FRAME_IN_L1_LIST_BIT_KHR` specifies support for using a B frame as L1 reference, as specified in `StdVideoEncodeH264ReferenceListsInfo`::`RefPicList1` in the H.264 picture information.

- `VK_VIDEO_ENCODE_H264_CAPABILITY_PER_PICTURE_TYPE_MIN_MAX_QP_BIT_KHR` specifies support for specifying different QP values in the members of VkVideoEncodeH264QpKHR.

- `VK_VIDEO_ENCODE_H264_CAPABILITY_PER_SLICE_CONSTANT_QP_BIT_KHR` specifies support for specifying different constant QP values for each slice.

- `VK_VIDEO_ENCODE_H264_CAPABILITY_GENERATE_PREFIX_NALU_BIT_KHR` specifies support for generating prefix NAL units by setting VkVideoEncodeH264PictureInfoKHR::`generatePrefixNalu` to `VK_TRUE`.

- `VK_VIDEO_ENCODE_H264_CAPABILITY_MB_QP_DIFF_WRAPAROUND_BIT_KHR` indicates support for wraparound during the calculation of the QP values of subsequently encoded macroblocks, as defined in equation 7-37 of the ITU-T H.264 Specification. If not supported, equation 7-37 of the ITU-T H.264 Specification is effectively reduced to the following:

  QPY = QPY,PREV + `mb_qp_delta`

  Note | The effect of this is that the maximum QP difference across subsequent macroblocks is limited to the [-(26 + QpBdOffsetY / 2), 25 + QpBdOffsetY / 2] range.

## See Also

VK_KHR_video_encode_h264, VkVideoEncodeH264CapabilityFlagsKHR

## 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 2014-2024 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0