An experimental study on the perceived quality of natively graded versus inverse tone mapped high dynamic range video co
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An experimental study on the perceived quality of natively graded versus inverse tone mapped high dynamic range video content on television Gonzalo Luzardo1,4 · Tine Vyvey1 · Jan Aelterman1 · Tom Paridaens2 · Glenn Van Wallendael2 · Peter Lambert2 · Sven Rousseaux3 · Hiep Luong1 · Wouter Durnez1 · Jan Van Looy1 · Wilfried Philips1 · Daniel Ochoa4 Received: 5 September 2019 / Revised: 17 August 2020 / Accepted: 17 September 2020 / © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract High Dynamic Range (HDR) television promises to display higher brightness and deeper black levels and thus more vivid and realistic images. However, home video distribution and video broadcasting were historically designed for what we now call standard dynamic range screens (SDR). In order to display SDR content on an HDR screen, it is explicitly or implicitly converted, in a process called inverse tone mapping (iTMO). This paper’s goal is to assess the perceived quality of converted SDR content in comparison to natively graded HDR content. In doing so, this paper aims to enable content creators/distributors to make informed choices between creating/broadcasting HDR content or relying on conversion. To this end, a psychophysical experiment was performed to tests how viewers evaluate the difference between natively graded HDR and a set of SDR to HDR conversion options in a television setup. Results indicate that viewers prefer natively graded HDR content, followed by inverse tone mapping algorithms starting from videos with a compressed dynamic range. When comparing conversion options, users clearly prefer conversion from ‘compressed dynamic range’ SDR over ‘clipped dynamic range’ SDR. Users disliked videos that were naively stretched from standard SDR. In addition, a significant effect of type of sequence was found, with a preference for light scenes with low contrast. Keywords High dynamic range · Inverse tone mapping · Subjective study
1 Introduction High Dynamic Range (HDR) is considered an important next step in the evolution of television technology. HDR imaging overcomes the dynamic range limitations of traditional imaging by capturing the full range of the visible light spectrum (e.g., highlights and deeper Gonzalo Luzardo
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tones) and colors that exist in the real world by performing operations at high bit-depths [6]. Dynamic range refers to the ratio between the brightest whites and darkest blacks present in an image, and it is commonly measured in f-stops (or simply stops), which is the logarithm of the ratio. The following definitions of the different types of Dynamic Ranges, based on the number of f-stops (the term f-stop refers to the contrast ratios), were adopted: Standard Dynamic Range (SDR) is ≤ 10 f-stops (also known as Low Dynamic Range (LDR)), Enhanced Dynamic Range (XDR) is > 10 f-stops and ≤ 16 f-stops, High Dynamic Ran
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