By Chris Seeger, NBC Universal, LLC
Developing video content for the extended dynamic range and color depth in high dynamic range (HDR) and wide color gamut (WCG) now common in consumer displays isn’t necessarily new: the first functional 4K/HDR televisions came out in 2016, and popular over-the-top (OTT) video platforms have routinely produced content in HDR since then. However; it is far, far more difficult to shoot and deliver HDR content for live linear workflows than it is for most file-based post produced approaches. That’s because in live HDR production environments, handling graphical placements, color correction, and luminance normalization across what is usually a mix of SDR (standard dynamic range, which is essentially contemporary HDTV) and HDR cameras must be done on-the-fly and in real-time.
Also, differences in system colorimetry exist within the primary HDR systems, specifically Hybrid Log Gamma (HLG) and Perceptual Quantizers (PQ), and took us some time to understand. A functional workflow for live delivery requires multiple levels of conversion for various signals throughout the infrastructure - like graphics, video playback, SDR and native HDR cameras. This three-part paper will explore 1) conversion and perceptual measurement for HDR and SDR; 2) how HDR production workflows are orchestrated for live content, and 3) how those live linear workflows are distributed – atopic likely of most interest to the cable television industry.
In addition, the paper will illuminate the research and collaborative processes necessary to build afunctional, single-stream HDR-SDR workflow, at each stage of the pipeline, without compromising the artistic intent or quality of the distribution paths for either the HDR or the primary (and revenue generating) SDR. In-depth research of color conversions will be discussed and explored, such as the specialized techniques described in the International Telecommunications Union – Radiocommunications Sector’s (ITU-R) Recommendation BT.2124. Production layouts will be explored and described, so that readers gain a deeper understanding of decisions made in the baseband (serial digital interface (SDI) and IP – Internet protocol), file-based conversions/transcodes, and orchestration layers.