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ABSTRACT

NHK has been developing 8K Super Hi-Vision (SHV), a member of ultra-high definition television (UHDTV).

This can provide an increased sense of presence and realness to viewers. 8K SHV has system parameters of 7,680×4,320 pixels, 120-Hz frame frequency, and wide-colour gamut.

With the addition of an extended image dynamic range feature, it is expected that 8K SHV can be further enhanced to become the true ultimate television system.

We first discuss requirements for extended image dynamic range television systems.

Then, we propose the essential system parameter values based on the requirements.

We introduce the specific parameter of video level corresponding to reference white to address highlights specifically.

The proposed system parameters are designed with consideration of compatibility with existing workflows and infrastructure.

We conducted an experiment to examine the influence of peak display luminance level on picture production and confirmed that production practices would be substantially changed to fully exploit the display capabilities of the increased luminance levels.

We also conducted experiments to determine the required conditions of black level and peak luminance level of displays in various viewing environments.

INTRODUCTION

The introduction of image systems with higher dynamic range and a wider colour gamut is a globally active topic.

International standardization of these systems for broadcasting service is also underway by ITU-R, which has given these systems the name “extended image dynamic range television” (EIDRTV).

Increased image dynamic range itself is not new; however, recent display technologies have made brighter television displays available without increasing the luminance of black using local-dimming technology.

This has enabled high dynamic range (HDR) displays.

Ultra-high definition television (UHDTV) is the next-generation television system.

This not only incorporates higher pixel numbers than high definition television (HDTV) but also higher frame frequencies and a wider colour gamut.

NHK has been developing 8K Super Hi-Vision (SHV) with system parameters of 7,680×4,320 pixels, 120-Hz frame frequency, and a wide-colour gamut to provide viewers with an increased sense of presence and the sense of realness (1).

Various pieces of SHV equipment such as cameras, displays, and interfaces have been developed (2,3).

UHDTV test broadcasting including 8K SHV via satellite is planned to be launched in 2016 and a practical broadcasting in 2018.

If UHDTV is complemented by an extended image dynamic range feature, it will be the true ultimate television system.

In this paper, we first discuss requirements for EIDRTV systems.

Then, based on the requirements, we propose essential system parameter values for EIDRTV. We also present the results of experiments, which include the influence of HDR display on program production, the perceptible black levels on displays, and the preferred peak display luminance levels, to explore the implications of EIDRTV systems.

REQUIREMENTS FOR EIDRTV SYSTEMS

Before specifying the system parameters for EIDRTV systems, the requirements should be first identified. ITU-R Working Party 6C has identified the following four major requirements for EIDRTV systems:

R.1 The system should be capable of producing a “step-change” improvement in viewer experience which can substantially increase brightness and detail in highlights, increase brightness and detail for diffuse reflecting objects while providing good detail in dark areas.

R.2 The system should have, where appropriate, a degree of compatibility with existing workflows and broadcaster (legacy) infrastructure.

R.3 The system should be applicable to a range of domestic viewing environments, preferences and displays (including mobile and tablets), and be cost effective for both consumers and broadcasters.

R.4 The system should have a defined reference display and viewing environment in order that there is consistency of images that are produced.

Tone Reproduction Issues of Current Television

There are cases where the tone reproduction of the current television system is obviously not sufficient.

Major examples would be the expression of specular objects, reduction of colour saturation with high brightness, and difficulties in the simultaneous presentation of differently illuminated parts in one scene (e.g., with/without sunlight).

EIDRTV should be the system to resolve these issues to satisfy Requirement 1.

Relative representation of luminance

Current television signals represent the relative luminance of the images between “black” and “white”.

As used in this context, “black” and “white” do not represent absolute luminance, rather relative luminance because “black” and “white” luminance varies depending on the viewing environment and display specification.

This permits viewers to view the same television programmes with different and appropriate screen luminance under various circumstances including indoor/outdoor and day/night.

This is a natural practice in broadcasting and should be retained in EIDRTV to satisfy Requirements 2 and 3.