Parameters in optical_flow_pyr_lk node ?

Parameters in optical_flow_pyr_lk node ?

Hi,

In VAD there is optical_flow_pyr_lk node.

I think parameter 2 and 3 in the node are for giving the key points that we are extracted.

In old_points (2) there are following things { ArrayType, Capacity, IsVirtual, Value }

Is the capacity is the number of Keypoints ? (If yes how we will get that ?)

Also in Value, there are some default values. What is the significance of that ?

 

I have tried setting different values for the optical_flow_pyr_lk node but it was giving error all the time saying "INVALID_PARAMETES"

Can anybody explain this ?

 

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Hi,

Is the capacity is the number of Keypoints ? (If yes how we will get that ?)

The capacity indicates the max number of items that can be stored, it can hold less but no more.
The number of keypoints is actually defined by the previous node – harris corners
from optical flow pyramid documentation :

The implementation shall return the same number of vx_keypoint_t structs in the new vx_array
that were in the older vx_array
so the number of key points is defined by the Harris Corners kernel, you can see how many keypoints should be outputted in param 7 - num_corners
(it does seem that if the capacity isn’t big enough the harris corner kernel only outputs as much keypoints as defined for its output array capacity)

Also in Value, there are some default values. What is the significance of that ?

Value is used when initializing an array in place. When a port with an array is connected by an edge it’s not used.

 

Regards,

Stav

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