## C Specification

The VkVideoEncodeH265RateControlInfoEXT structure is defined as:

// Provided by VK_EXT_video_encode_h265
typedef struct VkVideoEncodeH265RateControlInfoEXT {
VkStructureType                                     sType;
const void*                                         pNext;
uint32_t                                            gopFrameCount;
uint32_t                                            idrPeriod;
uint32_t                                            consecutiveBFrameCount;
VkVideoEncodeH265RateControlStructureFlagBitsEXT    rateControlStructure;
uint8_t                                             subLayerCount;
} VkVideoEncodeH265RateControlInfoEXT;

## Members

• sType is the type of this structure.

• pNext is NULL or a pointer to a structure extending this structure.

• gopFrameCount is the number of frames contained within the group of pictures (GOP), starting from an intra frame and until the next intra frame. If it is set to 0, the implementation chooses a suitable value. If it is set to UINT32_MAX, the GOP length is treated as infinite.

• idrPeriod is the interval, in terms of number of frames, between two IDR frames. If it is set to 0, the implementation chooses a suitable value. If it is set to 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.

• rateControlStructure is a VkVideoEncodeH265RateControlStructureFlagBitsEXT value specifying the expected encode stream reference structure, to aid in rate control calculations.

• subLayerCount specifies the number of sub layers enabled in the stream.

## Description

In order to provide H.265-specific stream rate control parameters, add a VkVideoEncodeH265RateControlInfoEXT structure to the pNext chain of the VkVideoEncodeRateControlInfoKHR structure in the pNext chain of the VkVideoCodingControlInfoKHR structure passed to the vkCmdControlVideoCodingKHR command.

The parameters from this structure act as a guidance for implementations to apply various rate control heuristics.

It is 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 in vkCmdEncodeVideoKHR. Additionally, it is not required for the video session to be reset if the inferred picture type does not match the actual picture type.

Valid Usage (Implicit)
• VUID-VkVideoEncodeH265RateControlInfoEXT-sType-sType
sType must be VK_STRUCTURE_TYPE_VIDEO_ENCODE_H265_RATE_CONTROL_INFO_EXT

• VUID-VkVideoEncodeH265RateControlInfoEXT-rateControlStructure-parameter
rateControlStructure must be a valid VkVideoEncodeH265RateControlStructureFlagBitsEXT value