Delta Angle Signaling for Luma Blocks in Video Compression
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Solution Overview
Problem
Current video coding technologies, such as AV1, inefficiently signal delta angles for luma blocks, leading to suboptimal compression and increased bitstream size due to signaling all delta angles regardless of neighboring block angles.
Innovation Solution
A method to determine and signal only a subset of allowed delta angles based on the absolute difference between the nominal angle of a current block and its neighboring blocks, using a cumulative density function (CDF) and mapping table, to optimize bitstream encoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all allowed delta angles are signaled for every current block, then the decoder can accurately reconstruct the prediction angle, but the bitstream size increases and compression efficiency decreases
Solution Approach 1:
The patent extracts and signals only the necessary subset of delta angles based on the comparison between current block nominal angle and neighboring block nominal angles. When the absolute difference is within the threshold, only a limited set of delta angles is signaled instead of all allowed delta angles, thereby reducing bitstream size while maintaining sufficient prediction accuracy.
Solution Approach 2:
The patent applies partial action by signaling only the required portion of delta angles rather than all possible delta angles. The encoder determines the minimum necessary set of delta angles to signal based on the angular difference criterion, avoiding excessive signaling of redundant angle information.
2Quantity of substance
If a subset of delta angles is signaled to reduce bitstream size, then compression efficiency improves, but the decoder may lack sufficient information for accurate prediction angle reconstruction
Solution Approach 1:
The patent performs preliminary comparison between the current block nominal angle and neighboring block nominal angles before encoding. Based on this preliminary assessment of the angular difference, the encoder pre-determines which subset of delta angles needs to be signaled, ensuring that the necessary information is prepared in advance for accurate reconstruction without over-signaling.
Solution Approach 2:
The patent dynamically changes the parameter of delta angle signaling based on the computed absolute difference between nominal angles. When the difference is small (within threshold), a reduced set of delta angles is signaled; when the difference is large, more delta angles are signaled. This adaptive parameter adjustment maintains prediction accuracy while optimizing bitstream size.
3Productivity
If delta angle signaling is performed without considering neighboring block angles, then the encoding process is simpler and faster, but compression efficiency is suboptimal due to redundant information transmission
Solution Approach 1:
The encoder performs a preliminary comparison operation between current block nominal angle and neighboring block nominal angles before the main encoding process. This preliminary step quickly identifies whether angle similarity exists, allowing the encoder to select the appropriate signaling mode (full delta angles or subset) in advance, avoiding redundant processing during the main encoding phase.
Solution Approach 2:
The patent applies different signaling strategies to different local situations based on the angular relationship between current and neighboring blocks. When neighboring blocks have similar nominal angles, a simplified signaling mode is used; when they differ significantly, a more comprehensive signaling mode is applied. This localized adaptation optimizes compression efficiency for each block based on its specific context.
Data Source
AI summary
Systems and methods for improved delta angle signaling for blocks in video compression are provided. A method includes encoding a bitstream that includes a picture. The encoding includes obtaining a nominal angle of a current block of the picture for intra prediction; obtaining a nominal angle of at least one neighboring block of the current block for intra prediction; determining whether to signal all allowed delta angles of the nominal angle of the current block, or only a subset of the allowed delta angles of the nominal angle of the current block, based on a comparison between the nominal angle of the current block and the nominal angle of the at least one neighboring block; and signaling, within the bitstream, all the allowed delta angles or the subset of the allowed delta angles of the nominal angle of the current block based on the determining.