Vulkan.Extensions.VK_KHR_calibrated_timestamps

vkGetPhysicalDeviceCalibrateableTimeDomainsKHR - Query calibrateable time domains

Description

If pTimeDomains is NULL, then the number of calibrateable time domains supported for the given physicalDevice is returned in pTimeDomainCount. Otherwise, pTimeDomainCount must point to a variable set by the application to the number of elements in the pTimeDomains array, and on return the variable is overwritten with the number of values actually written to pTimeDomains. If the value of pTimeDomainCount is less than the number of calibrateable time domains supported, at most pTimeDomainCount values will be written to pTimeDomains, and INCOMPLETE will be returned instead of SUCCESS, to indicate that not all the available time domains were returned.

Valid Usage (Implicit)

• physicalDevice must be a valid PhysicalDevice handle

• pTimeDomainCount must be a valid pointer to a uint32_t value

• If the value referenced by pTimeDomainCount is not 0, and pTimeDomains is not NULL, pTimeDomains must be a valid pointer to an array of pTimeDomainCount TimeDomainKHR values

Return Codes

Success

• INCOMPLETE

• SUCCESS

Failure

• ERROR_OUT_OF_DEVICE_MEMORY

• ERROR_OUT_OF_HOST_MEMORY

• ERROR_UNKNOWN

• ERROR_VALIDATION_FAILED

See Also

VK_EXT_calibrated_timestamps, VK_KHR_calibrated_timestamps, PhysicalDevice, TimeDomainKHR

vkGetCalibratedTimestampsKHR - Query calibrated timestamps

Description

The maximum deviation may vary between calls to getCalibratedTimestampsKHR even for the same set of time domains due to implementation and platform specific reasons. It is the application’s responsibility to assess whether the returned maximum deviation makes the timestamp values suitable for any particular purpose and can choose to re-issue the timestamp calibration call pursuing a lower deviation value.

Calibrated timestamp values can be extrapolated to estimate future coinciding timestamp values, however, depending on the nature of the time domains and other properties of the platform extrapolating values over a sufficiently long period of time may no longer be accurate enough to fit any particular purpose, so applications are expected to re-calibrate the timestamps on a regular basis.

Valid Usage

• The timeDomain value of each CalibratedTimestampInfoKHR in pTimestampInfos must be unique except for those with a value of TIME_DOMAIN_PRESENT_STAGE_LOCAL_EXT

Valid Usage (Implicit)

• device must be a valid Device handle

• pTimestampInfos must be a valid pointer to an array of timestampCount valid CalibratedTimestampInfoKHR structures

• pTimestamps must be a valid pointer to an array of timestampCount uint64_t values

• pMaxDeviation must be a valid pointer to a uint64_t value

• timestampCount must be greater than 0

Return Codes

Success

• SUCCESS

Failure

• ERROR_OUT_OF_DEVICE_MEMORY

• ERROR_OUT_OF_HOST_MEMORY

• ERROR_UNKNOWN

• ERROR_VALIDATION_FAILED

See Also

VK_EXT_calibrated_timestamps, VK_KHR_calibrated_timestamps, CalibratedTimestampInfoKHR, Device

VkCalibratedTimestampInfoKHR - Structure specifying the input parameters of a calibrated timestamp query

Valid Usage

• timeDomain must be one of the TimeDomainKHR values returned by getPhysicalDeviceCalibrateableTimeDomainsKHR

• If timeDomain is TIME_DOMAIN_SWAPCHAIN_LOCAL_EXT or TIME_DOMAIN_PRESENT_STAGE_LOCAL_EXT, the pNext chain must include a SwapchainCalibratedTimestampInfoEXT structure

Valid Usage (Implicit)

• sType must be STRUCTURE_TYPE_CALIBRATED_TIMESTAMP_INFO_KHR

• pNext must be NULL or a pointer to a valid instance of SwapchainCalibratedTimestampInfoEXT

• The sType value of each structure in the pNext chain must be unique

• timeDomain must be a valid TimeDomainKHR value

See Also

VK_EXT_calibrated_timestamps, VK_KHR_calibrated_timestamps, StructureType, TimeDomainKHR, getCalibratedTimestampsKHR, getCalibratedTimestampsKHR

VkTimeDomainKHR - Supported time domains

Description

• TIME_DOMAIN_DEVICE_KHR specifies the device time domain. Timestamp values in this time domain use the same units and are comparable with device timestamp values captured using cmdWriteTimestamp or cmdWriteTimestamp2 and are defined to be incrementing according to the timestampPeriod of the device.

• TIME_DOMAIN_PRESENT_STAGE_LOCAL_EXT specifies a time domain unique to a particular swapchain and a specific present stage. Timestamp values in this time domain are in units of nanosecond and are comparable only with other values from the same swapchain and present stage.

• TIME_DOMAIN_SWAPCHAIN_LOCAL_EXT specifies a time domain unique to a particular swapchain. Timestamp values in this time domain are in units of nanosecond and are comparable only with other values from the same swapchain.

• TIME_DOMAIN_CLOCK_MONOTONIC_KHR specifies the CLOCK_MONOTONIC time domain available on POSIX platforms. Timestamp values in this time domain are in units of nanoseconds and are comparable with platform timestamp values captured using the POSIX clock_gettime API as computed by this example:

An implementation supporting VK_KHR_calibrated_timestamps or VK_EXT_calibrated_timestamps will use the same time domain for all its Queue so that timestamp values reported for TIME_DOMAIN_DEVICE_KHR can be matched to any timestamp captured through cmdWriteTimestamp or cmdWriteTimestamp2 .

struct timespec tv;
clock_gettime(CLOCK_MONOTONIC, &tv);
return tv.tv_nsec + tv.tv_sec*1000000000ull;

• TIME_DOMAIN_CLOCK_MONOTONIC_RAW_KHR specifies the CLOCK_MONOTONIC_RAW time domain available on POSIX platforms. Timestamp values in this time domain are in units of nanoseconds and are comparable with platform timestamp values captured using the POSIX clock_gettime API as computed by this example:

struct timespec tv;
clock_gettime(CLOCK_MONOTONIC_RAW, &tv);
return tv.tv_nsec + tv.tv_sec*1000000000ull;

• TIME_DOMAIN_QUERY_PERFORMANCE_COUNTER_KHR specifies the performance counter (QPC) time domain available on Windows. Timestamp values in this time domain are in the same units as those provided by the Windows QueryPerformanceCounter API and are comparable with platform timestamp values captured using that API as computed by this example:

LARGE_INTEGER counter;
QueryPerformanceCounter(&counter);
return counter.QuadPart;

See Also

VK_EXT_calibrated_timestamps, VK_KHR_calibrated_timestamps, CalibratedTimestampInfoKHR, PastPresentationTimingEXT, SwapchainTimeDomainPropertiesEXT, getPhysicalDeviceCalibrateableTimeDomainsKHR, getPhysicalDeviceCalibrateableTimeDomainsKHR