DCT-domain image registration techniques for compressed video

An image registration technique for compressed video such as motion JPEG or the I-picture of MPEG is investigated in this paper. The proposed technique is based on the DCT (Discrete Cosine Transform) coefficient matching. First, the coarse edge features are extracted by applying several edge detectors to luminance DC coefficients. Each detector generates one difference map for a single input image. A threshold is set up for each difference map to produce a binary map. Then, the alignment parameters are determined based on the binary maps of both input images generated by the same detector. Finally, the actual displacement in the pixel domain is calculated by averaging parameters from all detectors. It is shown by experimental results that the proposed method reduces the computational cost of image registration dramatically as compared with the pixel domain and edge-based DCT domain registration techniques while achieving certain quality of composition.