Pyramidal LK Optical Flow

Algorithm used to track points from one frame to the next. More...

Data Structures
struct	VPIOpticalFlowPyrLKParams
	Structure that defines the parameters for vpiSubmitOpticalFlowPyrLK. More...

Enumerations
enum	VPIEpsilonType
	Defines the error measurement types. More...

Functions
VPIStatus	vpiInitOpticalFlowPyrLKParams (VPIOpticalFlowPyrLKParams *params)
	Initializes VPIOpticalFlowPyrLKParams with default values. More...
VPIStatus	vpiCreateOpticalFlowPyrLK (uint32_t backends, int32_t width, int32_t height, VPIImageFormat fmt, int32_t levels, float scale, VPIPayload *payload)
	Creates payload for vpiSubmitOpticalFlowPyrLK. More...
VPIStatus	vpiSubmitOpticalFlowPyrLK (VPIStream stream, uint32_t backend, VPIPayload payload, VPIPyramid prevPyr, VPIPyramid curPyr, VPIArray prevPts, VPIArray curPts, VPIArray trackingStatus, const VPIOpticalFlowPyrLKParams *params)
	Runs Pyramidal LK Optical Flow on two frames. More...

Detailed Description

Algorithm used to track points from one frame to the next.

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Data Structure Documentation

VPIOpticalFlowPyrLKParams

struct VPIOpticalFlowPyrLKParams

Structure that defines the parameters for vpiSubmitOpticalFlowPyrLK.

Definition at line 92 of file OpticalFlowPyrLK.h.

Collaboration diagram for VPIOpticalFlowPyrLKParams:

Data Fields
float	epsilon	Specifies the error for terminating the algorithm.
VPIEpsilonType	epsilonType	Specifies the tracking error type.
int32_t	numIterations	Specifies the number of iterations. Value must be >= 1 and <= 32.
uint32_t	termination	Specifies the termination criteria. It can be bitwise combination of VPI_TERMINATION_CRITERIA_ITERATIONS and VPI_TERMINATION_CRITERIA_EPSILON.
uint32_t	useInitialFlow	Uses initial estimations stored in curPts when this flag is not 0, otherwise prevPts is copied to curPts and is considered the initial estimate.
int32_t	windowDimension	Specifies the size of the window on which to perform the algorithm. Value must be >= 6 and <= 32.

Enumeration Type Documentation

VPIEpsilonType

enum VPIEpsilonType

#include <vpi/algo/OpticalFlowPyrLK.h>

Defines the error measurement types.

Enumerator
VPI_LK_ERROR_L1	L1 distance between previous feature and a next feature.

Definition at line 82 of file OpticalFlowPyrLK.h.

Function Documentation

vpiCreateOpticalFlowPyrLK()

VPIStatus vpiCreateOpticalFlowPyrLK	(	uint32_t	backends,
		int32_t	width,
		int32_t	height,
		VPIImageFormat	fmt,
		int32_t	levels,
		float	scale,
		VPIPayload *	payload
	)

#include <vpi/algo/OpticalFlowPyrLK.h>

Creates payload for vpiSubmitOpticalFlowPyrLK.

Parameters

[in]	backends	VPI backends that are eligible to execute the algorithm. Currently only one backend is accepted.
[in]	fmt	Specifies the format for the pyramid.
[in]	width,height	Specifies the dimensions of the pyramid on the finest resolution.
[in]	levels	Specifies the level of the pyramid.
[in]	scale	Specifies the scale of the pyramid.
[out]	payload	Pointer to memory where the created payload handle will be written to.

Returns

an error code on failure else VPI_SUCCESS.

vpiInitOpticalFlowPyrLKParams()

VPIStatus vpiInitOpticalFlowPyrLKParams

(

VPIOpticalFlowPyrLKParams *

params

)

#include <vpi/algo/OpticalFlowPyrLK.h>

Initializes VPIOpticalFlowPyrLKParams with default values.

Defaults:

• useInitialFlow = 0
• termination = VPI_TERMINATION_CRITERIA_ITERATIONS | VPI_TERMINATION_CRITERIA_EPSILON
• epsilonType = VPI_LK_ERROR_L1
• epsilon = 0
• windowDimension = 15
• numIterations = 6

Parameters

[in]

params

Structure to be filled with default values.

Returns

an error code on failure else VPI_SUCCESS

vpiSubmitOpticalFlowPyrLK()

VPIStatus vpiSubmitOpticalFlowPyrLK	(	VPIStream	stream,
		uint32_t	backend,
		VPIPayload	payload,
		VPIPyramid	prevPyr,
		VPIPyramid	curPyr,
		VPIArray	prevPts,
		VPIArray	curPts,
		VPIArray	trackingStatus,
		const VPIOpticalFlowPyrLKParams *	params
	)

#include <vpi/algo/OpticalFlowPyrLK.h>

Runs Pyramidal LK Optical Flow on two frames.

Outputs estimated feature points and tracking status.

Parameters

[in]	stream	The stream where the operation will be queued in.
[in]	backend	Backend that will execute the algorithm. Must be one of the backends specified during payload creation. If 0, VPI will select one of the eligible backends from the payload that accepts the given parameters, usually the fastest one.
[in]	payload	Payload created with vpiCreateOpticalFlowPyrLK
[in]	prevPyr	Previous frame, represented as a gaussian pyramid.
[in]	curPyr	Current frame, represented as a gaussian pyramid.
[in]	prevPts	array of keypoints in the prevPyr high resolution pyramid. The type of array must be VPI_ARRAY_TYPE_KEYPOINT.
[in,out]	curPts	array of keypoints in the curPyr high resolution pyramid. It is used as starting search point in curPyr if useInitialFlow is not 0. The type of array must be VPI_ARRAY_TYPE_KEYPOINT.
[in,out]	trackingStatus	Status array for tracking status for each input in prevPts. If element is one, the corresponding keypoint isn't being tracked, otherwise, it is. The type of the array must be VPI_ARRAY_TYPE_U8.
[in]	params	Parameters for the LK tracker. If NULL, it uses default parameters are returned by vpiInitOpticalFlowPyrLKParams.

Returns

an error code on failure else VPI_SUCCESS