Video Encoding Tone Map Adaptation for HDR Viewer Comfort
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Solution Overview
Problem
High dynamic range (HDR) video data captured by digital video cameras can exceed comfortable luminance limits for viewers adapted to prior ambient conditions, leading to discomfort during playback, especially when transitioning from dark to bright environments.
Innovation Solution
A method for encoding video data using a brightness adaptation model that adjusts tone maps based on ambient and measured light levels, ensuring peak luminance is reduced to comfortable levels for the viewer, with metadata indicating peak luminance levels for accurate reproduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If HDR video data is captured with full dynamic range, then luminance intensity range is improved, but viewer comfort deteriorates when luminance exceeds adaptation limits
Solution Approach 1:
The patent implements dynamic tone mapping that adapts to temporal changes in luminance levels. The system continuously monitors luminance intensity over time and adjusts the tone map parameters dynamically, allowing the video signal to adapt to the viewer's temporal adaptation state. This resolves the contradiction by making the luminance intensity range variable rather than fixed, expanding it when comfortable and compressing it when adaptation limits are approached.
Solution Approach 2:
The patent changes the luminance parameter representation by introducing a temporally variable peak luminance parameter derived from a brightness adaptation model. Instead of using fixed peak luminance values, the system calculates adaptive peak luminance parameters based on the duration and intensity of displayed luminance levels. This parameter transformation allows the system to preserve HDR quality while preventing viewer discomfort by adjusting the effective luminance range according to adaptation dynamics.
2Object-affected harmful factors
If peak luminance is reduced to comfortable levels, then viewer comfort is improved, but luminance intensity range is reduced
Solution Approach 1:
The patent applies preliminary tone mapping during the encoding stage to pre-adjust luminance levels according to the brightness adaptation model. By performing the luminance adjustment in advance rather than in real-time playback, the system can optimize the tone map parameters based on the entire video sequence characteristics. This preliminary action preserves the luminance intensity range in the encoded data while ensuring that displayed luminance remains within comfortable adaptation limits.
Solution Approach 2:
The patent introduces a brightness adaptation model as an intermediary between the HDR video source and the display device. This model acts as a mediator that transforms the full dynamic range luminance data into an adaptation-aware representation. The intermediary preserves the original luminance information while adding adaptation context, allowing the display to reproduce comfortable luminance levels without losing the underlying HDR quality.
3Adaptability or versatility
If tone map is dynamically adjusted, then adaptation to viewing conditions is improved, but encoding complexity increases
Solution Approach 1:
The patent implements a self-adapting encoding system that automatically determines tone map parameters based on the video content characteristics and predetermined brightness adaptation models. The system does not require manual intervention or complex real-time interaction; instead, it autonomously analyzes the luminance distribution and applies appropriate adaptation parameters. This self-service approach improves adaptability to viewing conditions while keeping encoding complexity manageable through automation rather than manual control.
Solution Approach 2:
The patent applies partial adaptation by focusing tone map adjustments on the most critical luminance parameters (particularly peak luminance) rather than adjusting all luminance levels uniformly. By concentrating adaptation efforts on the parameters that most significantly affect viewer comfort (the peak and temporal transitions), the system achieves effective adaptation with reduced computational complexity compared to full-spectrum luminance adjustment.
Data Source
AI summary
A method for encoding video data into a video bitstream using a video capture device having a brightness range limited output determines capture conditions for the capture device, the capture conditions including an ambient capture light level and a measured light level of captured video data. The method adjusts a brightness adaptation model using at least the measured light level and the ambient capture light level, the brightness adaption model defining a temporally variable peak luminance for a viewer of video captured using the capture device, and then determines a tone map such that where the measured light level exceeds a determined maximum light level the tone map is modified to reduce brightness, the maximum light level is determined using the brightness adaptation model. The captured video data is then encoded into the video bitstream using the determined tone map.