# VkVideoEncodeH264RateControlInfoKHR(3) Manual Page

## Name

VkVideoEncodeH264RateControlInfoKHR - Structure describing H.264 stream rate control parameters

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## C Specification

The `VkVideoEncodeH264RateControlInfoKHR` structure is defined as:

    // Provided by VK_KHR_video_encode_h264
    typedef struct VkVideoEncodeH264RateControlInfoKHR {
        VkStructureType                         sType;
        const void*                             pNext;
        VkVideoEncodeH264RateControlFlagsKHR    flags;
        uint32_t                                gopFrameCount;
        uint32_t                                idrPeriod;
        uint32_t                                consecutiveBFrameCount;
        uint32_t                                temporalLayerCount;
    } VkVideoEncodeH264RateControlInfoKHR;

## 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 VkVideoEncodeH264RateControlFlagBitsKHR specifying H.264 rate control flags.

- `gopFrameCount` is the number of frames within a group of pictures (GOP) intended to be used by the application. If it is 0, the rate control algorithm may assume an implementation-dependent GOP length. If it is `UINT32_MAX`, the GOP length is treated as infinite.

- `idrPeriod` is the interval, in terms of number of frames, between two IDR frames (see IDR period). If it is 0, the rate control algorithm may assume an implementation-dependent IDR period. If it is `UINT32_MAX`, the IDR period is treated as infinite.

- `consecutiveBFrameCount` is the number of consecutive B frames between I and/or P frames within the GOP.

- `temporalLayerCount` specifies the number of H.264 temporal layers that the application intends to use.

## Description

When an instance of this structure is included in the `pNext` chain of the VkVideoCodingControlInfoKHR structure passed to the vkCmdControlVideoCodingKHR command, and VkVideoCodingControlInfoKHR::`flags` includes `VK_VIDEO_CODING_CONTROL_ENCODE_RATE_CONTROL_BIT_KHR`, the parameters in this structure are used as guidance for the implementation’s rate control algorithm (see Video Coding Control).

If `flags` includes `VK_VIDEO_ENCODE_H264_RATE_CONTROL_ATTEMPT_HRD_COMPLIANCE_BIT_KHR`, then the rate control state is reset to an initial state to meet HRD compliance requirements. Otherwise the new rate control state may be applied without a reset depending on the implementation and the specified rate control parameters.

Note | It would be possible to infer the picture type to be used when encoding a frame, on the basis of the values provided for `consecutiveBFrameCount`, `idrPeriod`, and `gopFrameCount`, but this inferred picture type will not be used by implementations to override the picture type provided to the video encode operation.

Valid Usage

- VUID-VkVideoEncodeH264RateControlInfoKHR-flags-08280
  If VkVideoEncodeH264CapabilitiesKHR::`flags`, as returned by vkGetPhysicalDeviceVideoCapabilitiesKHR for the used video profile, does not include `VK_VIDEO_ENCODE_H264_CAPABILITY_HRD_COMPLIANCE_BIT_KHR`, then `flags` must not contain `VK_VIDEO_ENCODE_H264_RATE_CONTROL_ATTEMPT_HRD_COMPLIANCE_BIT_KHR`

- VUID-VkVideoEncodeH264RateControlInfoKHR-flags-08281
  If `flags` contains `VK_VIDEO_ENCODE_H264_RATE_CONTROL_REFERENCE_PATTERN_FLAT_BIT_KHR` or `VK_VIDEO_ENCODE_H264_RATE_CONTROL_REFERENCE_PATTERN_DYADIC_BIT_KHR`, then it must also contain `VK_VIDEO_ENCODE_H264_RATE_CONTROL_REGULAR_GOP_BIT_KHR`

- VUID-VkVideoEncodeH264RateControlInfoKHR-flags-08282
  If `flags` contains `VK_VIDEO_ENCODE_H264_RATE_CONTROL_REFERENCE_PATTERN_FLAT_BIT_KHR`, then it must not also contain `VK_VIDEO_ENCODE_H264_RATE_CONTROL_REFERENCE_PATTERN_DYADIC_BIT_KHR`

- VUID-VkVideoEncodeH264RateControlInfoKHR-flags-08283
  If `flags` contains `VK_VIDEO_ENCODE_H264_RATE_CONTROL_REGULAR_GOP_BIT_KHR`, then `gopFrameCount` must be greater than `0`

- VUID-VkVideoEncodeH264RateControlInfoKHR-idrPeriod-08284
  If `idrPeriod` is not `0`, then it must be greater than or equal to `gopFrameCount`

- VUID-VkVideoEncodeH264RateControlInfoKHR-consecutiveBFrameCount-08285
  If `consecutiveBFrameCount` is not `0`, then it must be less than `gopFrameCount`

Valid Usage (Implicit)

- VUID-VkVideoEncodeH264RateControlInfoKHR-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_VIDEO_ENCODE_H264_RATE_CONTROL_INFO_KHR`

- VUID-VkVideoEncodeH264RateControlInfoKHR-flags-parameter
  `flags` must be a valid combination of VkVideoEncodeH264RateControlFlagBitsKHR values

## See Also

VK_KHR_video_encode_h264, VkStructureType, VkVideoEncodeH264RateControlFlagsKHR

## 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