Escape Code Coding for Motion Vector Difference in Video
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Solution Overview
Problem
Current video coding standards, such as Versatile Video Coding (VVC), face inefficiencies in signaling motion vector differences (MVDs) due to the use of codewords with maximum lengths of 34 bits, which can be reduced to 32 bits for improved byte-alignment and reduced bit usage.
Innovation Solution
Coding MVD values using a codeword prefix of 1111 1111 1111 1111 and a fixed-length codeword suffix, allowing for a maximum of 32 bits to represent MVD values greater than 131070, thereby reducing the number of bits required for encoding and decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If codewords with maximum length of 34 bits are used to represent MVD values, then all MVD values can be represented, but the bit usage is excessive and byte-alignment is poor
Solution Approach 1:
The codeword is divided into two segments: a fixed prefix (16 bits) and a variable suffix (0-16 bits). The prefix indicates the magnitude range of the MVD value, while the suffix provides the specific value within that range. This segmentation allows the total codeword length to be reduced to maximum 32 bits while still representing all required MVD values.
Solution Approach 2:
Different parts of the codeword have different properties: the prefix uses a fixed pattern (16 bits of 1s) to indicate escape code activation, while the suffix uses variable-length encoding adapted to the specific MVD value range. This local differentiation optimizes the overall encoding efficiency.
2Productivity
If codeword length is reduced to 32 bits, then byte-alignment and processing efficiency improve, but the ability to represent very large MVD values is constrained
Solution Approach 1:
The codeword structure is designed to be dynamic in its suffix length while maintaining a fixed prefix. The suffix length adapts based on the MVD value being encoded, allowing the system to optimize between representing very large values and maintaining compact 32-bit alignment. This dynamic adjustment enables the prefix-suffix structure to flexibly accommodate different MVD magnitudes within the 32-bit constraint.
Data Source
AI summary
A device for coding video data is configured to code a motion vector difference (MVD) value using a codeword prefix and a codeword suffix. Based on an absolute value, minus 2, of the MVD value being 131070 or greater, the codeword prefix of the MVD value is equal to 1111 1111 1111 1111 and the codeword suffix is coded using the fixed length code.