Variable Segmented Lookup Tables for Video Signal Transfer
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Solution Overview
Problem
High dynamic range video systems require larger lookup tables (LUTs) to maintain image quality, leading to increased storage costs and processing time, while reducing LUT size using standard interpolation techniques introduces user-perceptible distortion.
Innovation Solution
Implementing a segmented lookup table with a variable segmentation step size, where each segment's step size is determined by video parameters to balance LUT size reduction with maintaining targeted video quality, using a segment index table for indirect indexing and potentially incorporating spline interpolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a full 4096 entry LUT is used to support the transfer function in high dynamic range systems, then video quality is maintained, but storage cost increases
Solution Approach 1:
The LUT is divided into multiple segments with different step sizes. Critical regions (dark shadows, bright highlights) use smaller step sizes to maintain quality, while less critical regions use larger step sizes to reduce storage. This segmentation allows the system to maintain video quality in important areas while reducing overall storage requirements from a full 4096-entry LUT.
Solution Approach 2:
Different portions of the LUT are assigned different qualities based on their importance. The patent applies smaller step sizes (higher precision) in critical regions such as dark shadows and bright highlights where human vision is more sensitive, and larger step sizes (lower precision) in mid-tone regions. This local quality approach maintains perceived video quality while reducing total storage cost.
2Quantity of substance
If LUT size is reduced using standard interpolation techniques, then storage cost decreases, but user perceivable distortion is introduced
Solution Approach 1:
Instead of uniformly reducing LUT size with standard interpolation, the patent segments the LUT and applies different step sizes to different segments. This allows aggressive compression in non-critical regions while maintaining fine resolution in critical regions, avoiding user-perceivable distortion in important areas like shadows and highlights.
Solution Approach 2:
The patent applies local quality by using smaller step sizes in regions where interpolation would cause visible distortion (dark and bright regions) and larger step sizes where distortion is less noticeable (mid-tones). This selective approach reduces storage cost while preventing user-perceivable distortion in critical areas.
3Measurement precision
If a larger LUT is used to support higher bit depth signals, then transfer function accuracy is improved, but processing time increases
Solution Approach 1:
The LUT is segmented into regions with different precision levels. The video processing system only needs to access and process entries in the segments relevant to the current video content, rather than processing the entire 4096-entry LUT. This segmentation reduces the effective processing time while maintaining transfer function accuracy in critical regions through appropriate step sizes.
Data Source
AI summary
The disclosure is directed to transforming signals from one signal format to another signal format. For example, the format of a digital signal can change from storing video information in 12 bits of data to storing the video information in 32 bits of data. Other storage values and combinations can also be used. Since the number of bits available to store a portion of the video information can change when changing formats, a process is needed to translate or transform the video information appropriately. A transfer function utilizing a lookup table is used for the transforming. The lookup table utilizes a variable step size segmentation scheme that decreases the amount of lookup table storage space required and also decreases the number of estimation errors, i.e., interpolation errors. Estimation errors can occur when looking up a value not stored in the lookup table, and using neighboring values that are stored to estimate the value requested. In some applications, the log2 step size or total size values can be stored in the lookup table to further reduce the amount of storage space required. A video parameter, such as the type of video content and the display room ambiance, can also be used to select the balance between further decreasing the size of the lookup table and further decreasing the estimation errors.