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Defining and Standardizing the Holography Media Production Workflow

February 7, 2022

In the Jan/Feb issue of The SMPTE Motion Imaging Journal,  Aaron Demolder presents his technical paper, “Toward the Standardization of High-Quality Computer-Generated Holography Media Production Workflow.” Demolder, a digital media engineering doctoral candidate at the Center for Digital Entertainment at the UK’s Bournemouth University, focuses on better incorporating emerging technology into art-driven pipelines. In this article, he examines the prospects for computer-generated holography (CGH) in television and cinema applications, proposing a suitable workflow for high-quality hologram delivery that allows it to integrate with existing methods of content production while delivering a rich holographic display experience.

A CGH display uses the interference of coherent light (such a lasers) to form 3D virtual imagery by shaping the wavefront of light using devices called spatial light modulators (SLMs) that can modulate the intensity and phase of the light beam. The engineered wavefronts of light diffract and propagate through space, forming a 3D image representing the original scene with the expected depth cues such as accommodation and parallax preserved. These are computational displays, meaning that the pixels worked on throughout the production process are not displayed directly on the final display device, but instead are encoded into an interference pattern (the most practical being image/layer-based holography) for display. As this type of display technology matures, applications such as augmented/virtual reality, heads up displays, and large screen display devices (discussed in this paper) will become practical.

There is currently no established practical workflow for delivering the required data to the hologram generation software, ensuring sufficient metadata for both standard dynamic range (SDR) and high-dynamic range (HDR) content, as well as the bit depth required for the high luminance of the laser and accurate color handing for any number of input color spaces. This significantly greater amount of data generated in the visual effects process for the most immersive experience would require 3D data representation, HDR specifications, and color specifications.

In the current 2D display, pixels contain information about the red, green, and blue channels, while for 3D holographic display, multiple color and depth values are required for each pixel as well. High-dynamic range in holographic display can achieved with a combination of bright laser illumination, a spatial light modulator that can replicate the diffraction pattern provided by the algorithm, an effective algorithm that provides sufficient black levels for a higher contrast ratio, and high bit-depth input image data. An accurate holographic color handling system also requires preserving creative intent by respecting existing spaces for content, enabling support for the Academy Color Encoding System (ACES), and providing display-referred space support for content made specifically with monochromatic laser primaries in mind.

In his paper, Demolder compares the workflow of a typical current content creation production workflow with that required to generate holograms. He also proposes a high-quality hologram delivery format -- combining a fully featured EXR (a high dynamic range image file format) container, full scene-referred workflow, luminance and color metadata, and a hologram algorithm standard – all packaged as per the Interoperable Master Format (IMF) framework, the SMPTE standard providing a single interchangeable master file format and structure for creating a true file-based final master.

For a deeper dive into the challenges of defining a complete workflow for the fast-developing field of holographic media production, read the complete article in The SMPTE Motion Imaging Journal.

Tag(s): Featured , HDR , CCD , News

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