A Template Matching Approach for Reference Picture Padding in Video Coding

Reference picture padding is needed in areas close to the picture boundary. It lifts the restriction of motion vectors not to point over the boundary when using inter prediction. Especially, when independently decodable subpictures are used e.g. in viewport-adaptive streaming, many boundaries occur, where padding is necessary. In such cases, the prediction quality of reference (sub)picture padding has an increased impact on the coding performance. Template matching has shown to work well for texture prediction in video coding. The paper shows that it also improves coding performance when applied in the context of reference picture padding. Experimental results on a set of test sequences demonstrate consistent coding gains and an average Bjøntegaard delta rate reduction of −0.38% and −0.48% for two sets of sequences with frequent utilization of reference picture padding. A drawback of template matching is its computational complexity. A preliminary investigation shows that the complexity can be reduced by a factor of 330 while maintaining about 60% of the Bjøntegaard delta rate savings.