Fast Template Matching-Based Reference Picture Padding for Video Coding

Reference Picture Padding is utilized in a variety of video coding standards. It allows motion vectors to point partly outside the reference picture in inter prediction. This approach provides advantages in compression efficiency. The method employed in current standards is repetative padding, which copies the pixels at the picture border outward. The major advantage of this approach is its low complexity. However, it is not optimal in terms of compression efficiency. Recently, motion-compensated padding has been introduced, which utilizes already coded content in the padding process. Another padding method is template matching-based padding, with the main downside being its high computational complexity. In this work, we propose a complexity reduction of the method by applying different measures, including an improved virtual target block increase and an early termination of the search, among other improvements. As a result, we achieve a decoder runtime increase of 1% and a BD-rate of -0.33% in a low delay subpicture scenario, outperforming motion-compensated padding with a decoder runtime increase of 9% and a BD-rate of -0.19%. In the random-access configuration we can show a consistent improvement by combining the methods over the stand-alone methods.