MV Advanced Optical Flow DirectShow Filter

The MontiVision Advanced Optical Flow filter is used to detect and visualise optical flow withhin a video stream. The filter uses an advanced feature tracking algorithm instead of the simple block matching algorithm used in the MV Optical Flow filter. The Motion I/O output pin signals if one or more of the feature points in the image move a pixel distance that is higher than the threshold. For example you can control the MV Recording filter to record a video stream only if there is motion within a scene. The Direction I/O output pin outputs the global direction of the motion vectors in degrees (0 to 360). The Magnification I/O output pin outputs the global magnification of the motion vectors. These pins are useful to determine direction and speed of a single moving object.

You can access the X and Y positions of the feature points directly through the IMVAdvanceOpticalFlow2 interface.

File:	AdvancedOpticalFlow.ax
CLSID:	CLSID_MVAdvancedOpticalFlow

Supported Interfaces

IMVAdvanceOpticalFlow

IMVAdvanceOpticalFlow2

IMVFilterInfo

IMVFilterData

IMVAbout

Supported COM Events

The filter supports following events through the IMVFilterEvents interface. Look at the filter events page for more information.

Event	Value	Description
MV_ALGORITHM_START_EVENT	0	A filter starts processing a video frame or sample.
MV_ALGORITHM_END_EVENT	1	A filter finishes processing a video frame or sample.

Supported I/O Pins

I/O Pin	Corresponding method	Discription
Motion Out [Boolean]	IMVAdvancedOpticalFlow::GetMotion	Returns the currently state of the motion detection flag. The flag is TRUE, if one or more motion vectors are higher than the defined threshold.
Direction [Double, Int16]	IMVAdvancedOpticalFlow::GetMotionDirection	Returns the global direction of the motion vectors in degrees.
Magnification[Double, Int16]	IMVAdvancedOpticalFlow::GetMotionMagnitude	Returns the global magnification of the motion vectors.
X Position [Int16]	IMVAdvancedOpticalFlow::GetMotionXPosition	Returns the average horizontal position of the motion.
Y Position [Int16]	IMVAdvancedOpticalFlow::GetMotionYPosition	Returns the average vertical position of the motion.

MV Advanced Optical Flow Property Page

Uses the IMVAdvanceOpticalFlow interface to setup the filter.

MontiVision Advanced Optical Flow DirectShow Filter Property Page

Draw optical flow onto video.	Draws motion vectors onto the video stream. The start point of the vector is the position of the feature point in the former image and the end of the vector is the position of the feature point in the current image.
Automatically select new feature points after X frames.	If this mode is enabled, new feature points used for tracking are automatically selected after a defined number of processed frames. If this mode is disabled, new feature points are selected after more than half of the initial number of feature points have been lost. A feature point is lost when the tracking algorithm isn't able to track the feature point.
Minimum distance between two feature points.	Minum distance between two feature points in pixel to avoid a large number of feature points selected within a small neighbourhood.
Feature point quality.	0.01 - A lot of feature points with poor quality are accepted 1.00 - Only brilliant feature points are accepted.
Motion Threshold	Threshold used for motion detection. If one feature point moved more than this threshold in pixel, the motion detection flag is set to TRUE, otherwise FALSE.