Intra Prediction Mode Estimation for Video Coding Bit Reduction
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Solution Overview
Problem
Current video coding techniques face inefficiencies in signaling intra prediction modes, particularly when the actual mode is far from the estimated mode, leading to suboptimal coding efficiency due to incorrect estimation methods.
Innovation Solution
The method determines a first and second most probable intra prediction mode for a current video block, selecting one as the estimate of the actual mode based on angular and non-angular modes, and uses this estimate to signal the actual mode using variable length coding, thereby reducing bit usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the actual intra prediction mode is signaled explicitly, then the signaling is straightforward and unambiguous, but the number of bits required increases
Solution Approach 1:
The patent applies preliminary action by determining an estimated actual intra prediction mode before signaling the difference. The encoder and decoder both pre-calculate the same estimated mode based on neighboring block modes, allowing the actual mode to be signaled as a small difference value rather than the full mode index, thus reducing bits while maintaining accuracy
Solution Approach 2:
The patent introduces an intermediary element - the estimated actual intra prediction mode - that mediates between the actual mode and the signaled difference. This intermediary allows the system to transmit only the difference value, reducing the quantity of data while preserving the ability to reconstruct the actual mode accurately
2Quantity of substance
If variable length coding is used to signal the actual intra prediction mode, then the number of bits is reduced, but the coding complexity increases
Solution Approach 1:
The patent changes the parameter being signaled from the absolute mode index to the difference between the actual mode and the estimated mode. This parameter transformation allows the use of more efficient variable length coding schemes, as the difference values have a different statistical distribution that can be exploited for compression, reducing bits while managing complexity through standardized VLC tables
3Quantity of substance
If the estimated actual intra prediction mode is inaccurate, then fewer bits are needed to signal the difference, but the coding efficiency deteriorates due to larger reconstruction errors
Solution Approach 1:
The patent implements feedback by using the modes of already-coded neighboring blocks to inform the estimation of the actual intra prediction mode for the current block. This feedback mechanism ensures that the estimation is context-aware and accurate, as neighboring blocks typically have similar prediction characteristics, thus maintaining reliability while enabling bit reduction through difference coding
4Productivity
If a simple estimation method is used for the actual intra prediction mode, then the processing is faster and simpler, but the estimation accuracy decreases leading to suboptimal coding
Solution Approach 1:
The patent performs preliminary calculation of the estimated actual intra prediction mode using a systematic method that combines modes from multiple neighboring blocks. This preliminary estimation is computed efficiently using simple operations on neighboring block modes, achieving both speed and accuracy by establishing a reasonable estimate before the actual coding decision is made
Data Source
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AI summary
A video coder can determine a first most probable intra prediction mode and a second most probable intra prediction mode for a current video block, and based on the first and second most probable intra prediction modes, determine an estimate of an actual intra prediction mode used to code the current video block. The estimate of the actual intra prediction mode can be determined by selecting one of the first most probable mode and the second most probable mode as the estimate of the actual intra prediction in response to both the first most probable mode and the second most probable mode being different angular prediction modes. The estimate of the actual intra prediction mode plus difference information can be used to identify the actual intra prediction mode used to code the current video block.