Content Production Technology on Hybrid Log-Gamma

NHK produces a variety of contents for 8K test satellite broadcasting. Recommendation ITU-R BT.2100 was standardized only during last year and we are currently in the process of testing and verifying the hybrid log-gamma (HLG) productions accordingly. For 4K-8K satellite broadcastings, which will be launched in 2018, we plan to extend the broadcasting time for longer than that of the test broadcasting. Therefore, producing considerably more contents is necessary. Currently, our main broadcasting service is HDTV; hence, it is important to produce the 8K, 4K and HD contents effectively. To decrease the burden of content production, we developed two signal converters and plan to use them for the content production including not only conversion of the signal formats but also simultaneous production of UHDTV and HDTV. One signal converter processes the signal conversion between two high dynamic range (HDR) transfer functions–HLG and Perceptual Quantization (PQ)–by means of Recommendation ITU-R BT.2100. In addition, we installed a semiautomatic conversion system between HDR and standard dynamic range (SDR) to adjust a few video parameters; gain, black offset, and compression level of high luminance. It allows video engineers to compare HDR with SDR, which is converted from HDR side by side at the simultaneous production. The down-converter from UHDTV to HDTV, however, supports conversion of color gamut and dynamic range simultaneously. To reduce the deterioration of the color gradation in the conversion from Rec. 2020 to Rec. 709, we used a method based on the color perceptual model. In addition, it features a function that enhances the edge of the images based on specific spatial frequency after the down-conversion. In this paper, we describe the use cases of HLG content production using the converters and evaluate their effectiveness. Moreover, we show the high quality content production using the specific parameters for simultaneous production of UHDTV and HDTV contents.