Content-adaptive up-scaling of chrominance using classification of luminance and chrominance data

In a Standard Definition (SD) Television system, the Y:U:V video format 4:2:2 with chrominance sub-sampling is widely used. With the advent of High Definition (HD) television, the 4:4:4 format is required for high-performance TV. High-quality up-sampling methods have been developed to perform a resolution conversion from Standard Definition (SD) signal to HD signal. Although these algorithms have been designed for spatial scaling of luminance, they may be adapted and used to up-sample the low-resolution components U,V (4:2:2) to a high-resolution UV-colour format (4:4:4). In this paper, a content-adaptive up-scaling method for chrominance is proposed, with interpolation filters that adapt to the local structure of both luminance and chrominance data. Optimal filters were computed from a large video data set in different colour formats, such that original high-resolution data in a 4:4:4 format was reconstructed from low-resolution colour data, on the basis of the Least Mean Square (LMS) criterion. By combining edge information of both luminance and chrominance, the edge in the chrominance signal can be detected more accurately, thus exploiting the wider bandwidth of the luminance signal.