Customer feedback on 4K UHD tells us that more pixels alone will not satisfy market expectations for a next-generation broadcasting format. Having better pixels with a higher dynamic range is therefore a hot topic of discussion.
HDR is a major topic in the broadcast industry and for good reason. With HDR, a much improved viewer experience can be achieved fully independent from the screen size or other specific viewer conditions. In addition, HDR offers all this without an excessive amount of additional bandwidth or an increased data rate. Some might want to combine these advantages with the current HD formats or use them in combination with full progressive HD formats delivering any of the advanced 1080p formats.
Initially, a fully parallel HDR/SDR production using two kinds of cameras, or using the simultaneous HDR/SDR processing inside the cameras might be acceptable. But for cost and efficiency reasons, a more simplified workflow with an HDR and an SDR signal is required for the best performance of both systems.
In searching for the best HDR/SDR compatible workflow delivering the best SDR quality possible, we discussed and compared several HDR-to-SDR down-mapping methods. As a result, a system was proposed where the setting of the maximum output range in PQ (e.g. 1000, 2000, 4000, 10000 NITS) and the colorspace provided using the ITP domain for down-mapping. With this method, the luminance signal can be remapped with the required range without limiting the quality of the color reproduction such as generating color shifts.
An SDR-to-HDR up-mapping can be realized by setting the 100 percent reference point in the HDR OETF to a certain level and mapping the signal into the lower part of the HDR signal. By that, the signals look identical on an SDR monitor as well as on an HDR monitorwhich is an important assumption in using this workflow.
This paper explores the details of a potential solution for an SDR/HDR-compatible workflow for live production, based around HDR/SDR re-mapping.
- Klaus & Jeroen