Parity Hiding Reduces Context-Coded Bins in Video Coefficients
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Solution Overview
Problem
Current video encoding standards, such as H.264/AVC and developing HEVC, face inefficiencies in encoding and decoding transform coefficients, particularly due to the high percentage of bits occupied by encoding the last significant coefficient position, significance map, magnitudes, and signs of non-zero coefficients, which can lead to suboptimal compression efficiency.
Innovation Solution
The method involves using parity to hide information about the upper left coefficient in a coefficient group, conditional decoding of significant-coefficient and greater-than-one flags based on the parity of the upper left coefficient, and adjusting encoding/decoding processes to reduce the number of context-coded bins, thereby improving compression efficiency without sacrificing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If traditional encoding methods are used to encode all coefficients including the upper left coefficient, then complete information is preserved, but the number of context-coded bins increases and compression efficiency deteriorates
Solution Approach 1:
The patent extracts the upper left coefficient from the standard encoding process by determining its parity and using this parity information to conditionally decode other coefficients in the coefficient group, eliminating the need to explicitly encode the upper left coefficient itself while preserving necessary information
Solution Approach 2:
The patent introduces parity as an intermediary representation of the upper left coefficient. Instead of encoding the coefficient directly, the parity (even/odd status) serves as a mediator that enables conditional decoding of other coefficients in the group, reducing the number of bins required
2Measurement precision
If the upper left coefficient is always encoded with flags, then decoding accuracy is maintained, but the worst-case throughput of context-coded bins increases
Solution Approach 1:
The patent makes the decoding process dynamic by conditionally decoding coefficients based on the parity of the upper left coefficient. When parity is even, different coefficients are decoded compared to when parity is odd, allowing the system to adapt the number of flags used based on the actual data characteristics
Solution Approach 2:
The patent changes the parameter being encoded from the full coefficient value to its parity (even/odd status). This parameter transformation reduces the information needed to represent the upper left coefficient while still enabling accurate reconstruction of other coefficients in the group through conditional decoding
Data Source
AI summary
Methods and devices for reconstructing coefficient levels from a bitstream of encoded video data for a coefficient group in a transform unit. Parity hiding is used to signal the parity of the upper left coefficient of the coefficient group. Based on the parity, either the significant coefficient flag or the greater-than-one flag is encoded/decoded for that coefficient, but not both. The greater-than-one flag is encoded/decoded irrespective of whether a maximum number of greater-than-one flags have been encoded/decoded with respect to the other coefficients in the coefficient group.