Converting Ultrahigh-Definition Video Into Digital Cinema by Using Time-Expanding Bi-Directional Motion Estimation and Higher Green Frequency

Ultrahigh-definition television (UHDTV) is the next-generation ultrahigh-resolution video system with more than 4000 lines, and 7680 horizontal pixels × 4320 vertical lines at 60 f/s (frames per second) in video format. We propose a method of converting high-quality UHDTV video to digital cinema video that is 3840 horizontal pixels × 2160 vertical lines at 24 f/s. Here, it is important to detect motion vectors extremely accurately to convert the frame rate. We introduced two new algorithms to increase the accuracy of detecting motion vectors. First, we introduced a method of interpolation frames using 1/2 block-shift bi-directional motion estimation by expanding the time axis. The experimental results revealed that our new method produced higher quality video images than conventional methods of video conversion using forward-directional and overlapped block bi-directional motion estimation. Next, we focused on Bayer pattern sampling in existing UHDTV, and introduced a motion-compensated method of interpolation where the first algorithm utilizes the high-frequency components from green signals. The experimental results demonstrated that our proposed method achieves higher quality video conversions than conventional methods using only the first algorithm for motion-compensated interpolation, linear interpolation, and 5:2 frame skipping.