Tone Mapping System Temporal Coherency
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Solution Overview
Problem
Current HDR video tone mapping techniques lack temporal coherency, resulting in abrupt brightness changes between frames, which restricts their use due to perceived flashes by the human eye.
Innovation Solution
A tone mapping system that generates a base layer from HDR video frames, derives a tone curve parameter, and applies temporal filtering only to this parameter to smooth out inconsistencies between frames, generating a temporally coherent base layer without requiring extensive computing resources, while preserving detail by applying the tone curve only to the base layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional tone mapping techniques are applied to HDR video, then color range is adjusted to match display device capabilities, but temporal coherency is lost resulting in abrupt brightness changes between frames
Solution Approach 1:
The video signal is segmented into base layer and detail layer through high-pass filtering. The tone mapping operation is applied only to the base layer, which contains the low-frequency information responsible for overall brightness. This segmentation allows tone mapping to adapt colors while preserving temporal coherency by excluding the high-frequency detail information that would cause abrupt changes between frames.
Solution Approach 2:
Different processing approaches are applied to different frequency components of the video signal. The base layer receives tone mapping operations for color range adaptation, while the detail layer is preserved without tone mapping to maintain temporal stability. This local quality approach ensures that each component is processed according to its specific characteristics.
2Stability of the object's composition
If tone mapping is applied to entire video frames to ensure temporal coherency, then brightness stability is improved, but computing resources are extensively consumed
Solution Approach 1:
The high-pass filter extracts the detail layer from the original video signal, separating it from the base layer. By taking out only the necessary detail information and applying tone mapping exclusively to the base layer, the computing resources required are significantly reduced compared to processing entire frames, while still achieving temporal coherency in the final reconstructed video.
Solution Approach 2:
Instead of applying tone mapping to the entire video frame (excessive action), the method applies tone mapping only to the base layer (partial action). This partial application is sufficient to achieve temporal coherency and color range adaptation, avoiding the unnecessary computational overhead of processing the complete frame data.
3Adaptability or versatility
If tone mapping converts HDR video colors to display device range, then color compatibility is improved, but abrupt brightness changes occur between consecutive frames
Solution Approach 1:
The high-pass filtering operation is performed preliminarily to separate the base layer from the detail layer before tone mapping is applied. This preliminary action prepares the signal by isolating the components that will and will not undergo tone mapping, preventing abrupt brightness changes from occurring in the final output while maintaining color compatibility.
Data Source
AI summary
Embodiments herein disclose a tone mapping system that generates a base layer by filtering a frame in an HDR video. The tone mapping system then generates a tone curve using a tone mapping parameter derived from the base layer—e.g., a mean or maximum luminance value. Once the tone curve parameter is identified, the system performs temporal filtering to smooth out inconsistencies between the current value of the tone curve parameter and the values of tone curve parameter of at least one previous frame in the HDR video. The tone mapping system applies the temporally filtered tone curve to the base layer to generate a temporally coherent layer. The temporally coherent base layer can be combined with a detail layer derived from the HDR video to generate a frame of a tone mapped video.