VkVideoEncodeH264RateControlLayerInfoKHR(3)

# VkVideoEncodeH264RateControlLayerInfoKHR(3) Manual Page

## Name

VkVideoEncodeH264RateControlLayerInfoKHR - Structure describing H.264 per-layer rate control parameters

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## C Specification

The `VkVideoEncodeH264RateControlLayerInfoKHR` structure is defined as:

    // Provided by VK_KHR_video_encode_h264
    typedef struct VkVideoEncodeH264RateControlLayerInfoKHR {
        VkStructureType                  sType;
        const void*                      pNext;
        VkBool32                         useMinQp;
        VkVideoEncodeH264QpKHR           minQp;
        VkBool32                         useMaxQp;
        VkVideoEncodeH264QpKHR           maxQp;
        VkBool32                         useMaxFrameSize;
        VkVideoEncodeH264FrameSizeKHR    maxFrameSize;
    } VkVideoEncodeH264RateControlLayerInfoKHR;

## Members

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

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

- `useMinQp` indicates whether the QP values determined by rate control will be clamped to the lower bounds on the QP values specified in `minQp`.

- `minQp` specifies the lower bounds on the QP values, for each picture type, that the implementation’s rate control algorithm will use when `useMinQp` is set to `VK_TRUE`.

- `useMaxQp` indicates whether the QP values determined by rate control will be clamped to the upper bounds on the QP values specified in `maxQp`.

- `maxQp` specifies the upper bounds on the QP values, for each picture type, that the implementation’s rate control algorithm will use when `useMaxQp` is set to `VK_TRUE`.

- `useMaxFrameSize` indicates whether the implementation’s rate control algorithm should use the values specified in `maxFrameSize` as the upper bounds on the encoded frame size for each picture type.

- `maxFrameSize` specifies the upper bounds on the encoded frame size, for each picture type, when `useMaxFrameSize` is set to `VK_TRUE`.

## Description

When used, the values in `minQp` and `maxQp` guarantee that the effective QP values used by the implementation will respect those lower and upper bounds, respectively. However, limiting the range of QP values that the implementation is able to use will also limit the capabilities of the implementation’s rate control algorithm to comply to other constraints. In particular, the implementation may not be able to comply to the following:

- The average and/or peak bitrate values to be used for the encoded bitstream specified in the `averageBitrate` and `maxBitrate` members of the VkVideoEncodeRateControlLayerInfoKHR structure.

- The upper bounds on the encoded frame size, for each picture type, specified in the `maxFrameSize` member of `VkVideoEncodeH264RateControlLayerInfoKHR`.

| Note In general, applications need to configure rate control parameters appropriately in order to be able to get the desired rate control behavior, as described in the Video Encode Rate Control section.

When an instance of this structure is included in the `pNext` chain of a VkVideoEncodeRateControlLayerInfoKHR structure specified in one of the elements of the `pLayers` array member of the VkVideoEncodeRateControlInfoKHR structure passed to the vkCmdControlVideoCodingKHR command, VkVideoCodingControlInfoKHR::`flags` includes `VK_VIDEO_CODING_CONTROL_ENCODE_RATE_CONTROL_BIT_KHR`, and the bound video session was created with the video codec operation `VK_VIDEO_CODEC_OPERATION_ENCODE_H264_BIT_KHR`, it specifies the H.264-specific rate control parameters of the rate control layer corresponding to that element of `pLayers`.

Valid Usage

- VUID-VkVideoEncodeH264RateControlLayerInfoKHR-useMinQp-08286
  If `useMinQp` is `VK_TRUE`, then the `qpI`, `qpP`, and `qpB` members of `minQp` must all be between VkVideoEncodeH264CapabilitiesKHR::`minQp` and VkVideoEncodeH264CapabilitiesKHR::`maxQp`, as returned by vkGetPhysicalDeviceVideoCapabilitiesKHR for the used video profile

- VUID-VkVideoEncodeH264RateControlLayerInfoKHR-useMaxQp-08287
  If `useMaxQp` is `VK_TRUE`, then the `qpI`, `qpP`, and `qpB` members of `maxQp` must all be between VkVideoEncodeH264CapabilitiesKHR::`minQp` and VkVideoEncodeH264CapabilitiesKHR::`maxQp`, as returned by vkGetPhysicalDeviceVideoCapabilitiesKHR for the used video profile

- VUID-VkVideoEncodeH264RateControlLayerInfoKHR-useMinQp-08288
  If `useMinQp` is `VK_TRUE` and VkVideoEncodeH264CapabilitiesKHR::`flags`, as returned by vkGetPhysicalDeviceVideoCapabilitiesKHR for the used video profile, does not include `VK_VIDEO_ENCODE_H264_CAPABILITY_PER_PICTURE_TYPE_MIN_MAX_QP_BIT_KHR`, then the `qpI`, `qpP`, and `qpB` members of `minQp` must all specify the same value

- VUID-VkVideoEncodeH264RateControlLayerInfoKHR-useMaxQp-08289
  If `useMaxQp` is `VK_TRUE` and VkVideoEncodeH264CapabilitiesKHR::`flags`, as returned by vkGetPhysicalDeviceVideoCapabilitiesKHR for the used video profile, does not include `VK_VIDEO_ENCODE_H264_CAPABILITY_PER_PICTURE_TYPE_MIN_MAX_QP_BIT_KHR`, then the `qpI`, `qpP`, and `qpB` members of `maxQp` must all specify the same value

- VUID-VkVideoEncodeH264RateControlLayerInfoKHR-useMinQp-08374
  If `useMinQp` and `useMaxQp` are both `VK_TRUE`, then the `qpI`, `qpP`, and `qpB` members of `minQp` must all be less than or equal to the respective members of `maxQp`

Valid Usage (Implicit)

- VUID-VkVideoEncodeH264RateControlLayerInfoKHR-sType-sType
  `sType` must be `VK_STRUCTURE_TYPE_VIDEO_ENCODE_H264_RATE_CONTROL_LAYER_INFO_KHR`

- VUID-VkVideoEncodeH264RateControlLayerInfoKHR-minQp-parameter
  `minQp` must be a valid VkVideoEncodeH264QpKHR structure

- VUID-VkVideoEncodeH264RateControlLayerInfoKHR-maxQp-parameter
  `maxQp` must be a valid VkVideoEncodeH264QpKHR structure

- VUID-VkVideoEncodeH264RateControlLayerInfoKHR-maxFrameSize-parameter
  `maxFrameSize` must be a valid VkVideoEncodeH264FrameSizeKHR structure

## See Also

VK_KHR_video_encode_h264, VkBool32, VkStructureType, VkVideoEncodeH264FrameSizeKHR, VkVideoEncodeH264QpKHR

## 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 2014-2023 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0