Achieving True HDR Below 12 Bits Is ‘Content-Dependent,’ Says Dolby Engineer

It’s “content-dependent” whether true high dynamic range can be achieved in post-production at 10 bits, said Raymond Yeung, Dolby Labs senior staff engineer-Imaging R&D Group. “There are plenty of instances where work can be done in 10 bits,” Yeung told a Society of Motion Picture and TV Engineers webinar Thursday to show how SMPTE standards ST 2084, ST 2086 and ST 2094 can be used as “building blocks” for HDR content creation and distribution. But for “a lot of manipulation processing” that’s required during HDR post-production, “you do want to have enough bit depth,” Yeung said. For example, a professional monitor capable of black levels of 0.005 nits but also peak luminance of 4,000 nits has an 800,000:1 contrast ratio “in linear terms,” he said. For HDR content encoded for that monitor in 12 bits, using the perceptual quantization curve specified in SMPTE standard ST 2084, “you are fine, but anything less than that could be risky, and that’s my advice,” he said. Responding to a question on how the differences between 12-bit HDR professional monitors and 10-bit consumer HDR TVs can be accommodated, Yeung said he can’t predict whether “commercial technology will go towards 12 bits or not.” To “really answer the question, we’ll have to wait and see,” he said. “But I think 10 bits, it’s a good place to start,” he said of consumer HDR products.