Digital Image Stabilisation with Sub-Image Phase Correlation Based Global Motion Estimation

Digital Image Stabilisation with Sub-Image Phase Correlation Based Global Motion Estimation

Global motion is estimated from the local motions of four sub images each of which is detected using phase correlation based motion estimation. The global motion vector is decided according to the peak values of sub-image phase correlation surfaces, instead of impartial median filtering. The peak values of sub-image phase correlation surfaces reveal reliable local motion vectors, as poorly matched sub images result in considerably lower peaks in the phase correlation surface due to spread.

Digital image stabilization systems aim to remove irregular global motion effects from an image sequence in order to obtain a compensated sequence that displays smooth camera movements only

The digital image stabilization system can be divided into two parts: the global motion estimation systems and the motion correction system. The motion estimation system is responsible for the estimation of interframe global motion vectors, which are forwarded to the motion correction system. The motion correction system accomplishes the stabilization of the image sequence according to the global motion model or objective

The global motion vector of the image frame can then be decided based on the peak amplitude values of local motion vectors. Three different approaches can be utilized to evaluate the global motion:

1. The local motion vector with the largest peak amplitude

can be assigned as the global interframe motion vector.

2. The two highest peak amplitude values can be detected and the corresponding two local motion vectors can be averaged to obtain the global interframe motion vector.

If the result of the averaging is not an integer, the result is rounded to the nearest integer towards the motion vector with the highest peak amplitude.

3. All local motion vectors, not previously discarded, can be weighted proportionally to their peak amplitude values and the result can be assigned as the global interframe motion vector.