Depth Lookup Table Coding Using Constrained Value Ranges
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Solution Overview
Problem
The existing Depth Lookup Table (DLT) coding methods in 3D video coding are inefficient due to the use of Exp-Golomb codes, which are not optimal for encoding depth values with varying probabilities, resulting in a significant increase in bitstream size, especially for depth components, contributing more than 65% of the Sequence Parameter Set (SPS) bits.
Innovation Solution
A method for encoding and decoding depth lookup tables using a constrained table value range, where the minimum and maximum table values are coded as unsigned integers, and bit map values indicate whether depth values are in the DLT, employing run-length coding or differential coding to reduce bit usage, and optionally using inter-view coding for dependent views.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Exp-Golomb codes are used for encoding depth values in DLT, then the coding process is simple, but the bitstream size increases significantly
Solution Approach 1:
The patent changes the coding parameters by using constrained table value ranges instead of full-range depth values. By limiting the DLT to a specific range (e.g., 0-15 or 0-31 instead of 0-255), the patent enables more efficient coding methods that reduce bitstream size while maintaining coding feasibility.
Solution Approach 2:
The patent segments the depth value range into multiple constrained ranges, each with its own DLT. This segmentation allows different coding strategies to be applied to different ranges, optimizing the overall bitstream efficiency while maintaining simplicity in each segment's coding process.
2Measurement precision
If full-range DLT values (0-255) are coded, then the depth mapping accuracy is maintained, but the bitstream size increases by more than 65% of SPS bits
Solution Approach 1:
The patent introduces dynamic range selection where the DLT can operate in different value ranges (constrained or full-range) depending on the specific application requirements. This dynamic approach allows the system to adapt between accuracy and bitstream size based on the depth map characteristics and viewing requirements.
Solution Approach 2:
The patent changes the value range parameter of the DLT from fixed full-range (0-255) to configurable constrained ranges. By adjusting this parameter, the system can achieve optimal balance between depth mapping accuracy and bitstream efficiency for different scenarios.
3Quantity of substance
If constrained table value range is used in DLT, then the bitstream size is reduced, but the depth value coverage is limited
Solution Approach 1:
The patent segments the overall depth range into multiple constrained DLT ranges. By dividing the full depth space into several constrained segments, the system achieves efficient coding within each segment while collectively covering the entire depth range, thus maintaining versatility without sacrificing bitstream efficiency.
Solution Approach 2:
The patent makes the DLT system universal by enabling it to handle both constrained and full-range scenarios. The same DLT infrastructure can be configured for different value ranges, making it adaptable to various depth map types and application requirements while maintaining coding efficiency.
Data Source
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AI summary
A method and apparatus for encoding and decoding depth lookup table (DLT) using a constrained table value range are disclosed. For a decoder, a constrained table value range from a minimum table value to a maximum table value of the DLT is decoded from the coded DLT information. Bit map values for depth values in a depth range from (the minimum table value + ) to (the maximum table value -1) are then decoded. The bit map values indicate whether the depth values are in the DLT respectively. The DLT for the current depth map can be reconstructed based on the constrained table value range and the bit map values for the depth values in the depth range. For an encoder, a constrained table value range from a minimum table value to a maximum table value of the DLT is determined and encoded the DLT into coded DLT information.