Fast camera motion estimation using discrete wavelet transform on block motion vectors

In this paper we propose to use the discrete wavelet transform on the block motion vector field for estimating the camera (global) motion parameters in the compressed domain. By taking the wavelet transform of the block motion vector field we get the decomposition of the motion vectors into wavelet sub-bands. The LL sub-band gives us the average motion which we assume is mainly due to the background (camera) motion. By using gradient descent regression on LL sub-band wavelet coefficients we extract the camera motion parameters. Our results show that LL sub-band is enough to estimate the camera motion parameters unlike previous methods which utilize the entire block motion vector field to carry out the estimation process. Our experimental results demonstrate significant gain in processing time at the cost of marginal drop of estimation accuracy for the camera motion parameters. Our proposed technique finds its application in video indexing and video shot segmentation where fast camera motion estimation is warranted.