VST XR Local Tone Mapping for Edge-Preserving HDR-to-SDR Video
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Solution Overview
Problem
Video see-through (VST) XR systems face challenges in converting high dynamic range (HDR) image frames to standard dynamic range (SDR) frames, which often results in smoothing of object edges and blurring artifacts due to prior approaches that reduce contrast uniformly across the image.
Innovation Solution
A tone mapping filter is applied to the luminance channel of HDR image frames, guided by image and feature information, to transform the frames into SDR while preserving edge details, using techniques like local tone mapping and look-up tables for efficient conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If uniform contrast reduction is applied across the image for HDR to SDR conversion, then the dynamic range is successfully reduced, but object edges are smoothed and blurring artifacts occur
Solution Approach 1:
The patent applies local tone mapping that processes different regions of the image with different contrast reduction factors. Edge regions are identified and preserved with higher contrast, while non-edge regions undergo stronger contrast reduction. This local differentiation resolves the contradiction by maintaining edge sharpness in critical areas while still achieving overall dynamic range reduction.
Solution Approach 2:
The image is segmented into edge regions and non-edge regions through edge detection algorithms. This segmentation allows the tone mapping process to treat different regions differently, applying aggressive contrast reduction only where it won't harm edge quality, thus resolving the contradiction between dynamic range reduction and edge preservation.
2Reliability
If tone mapping is applied to all channels including chrominance, then comprehensive color and luminance adjustment is achieved, but computational resources increase
Solution Approach 1:
The patent extracts and processes only the luminance channel for tone mapping, separating it from the chrominance channels. This extraction allows the system to achieve the essential dynamic range reduction and image quality improvement without the computational overhead of processing all color channels, thus resolving the contradiction between reliability and productivity.
Solution Approach 2:
The patent applies tone mapping selectively to only the luminance channel rather than all channels. This partial action is sufficient to achieve the primary goal of dynamic range reduction and image quality improvement, while significantly reducing computational requirements compared to full-channel processing.
Data Source
AI summary
A method includes obtaining first image frames having a first dynamic range captured using at least one imaging sensor of a VST XR device. The method also includes, for each of at least one of the first image frames, generating a tone mapping filter configured to provide noise reduction and edge preservation while being guided by image and feature information and applying the tone mapping filter to the first image frame in order to transform the first image frame into a second image frame having a second dynamic range smaller than the first dynamic range. The tone mapping filter is applied to a luminance channel and not chrominance channels associated with the first image frame. The method further includes presenting one or more rendered images or videos based on the second image frame for each of at least one of the first image frames using at least one display.