Merge Flag Coding With Zero-Motion Candidates for Robust Video Parsing
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Solution Overview
Problem
The existing merge mode in HEVC video coding standards results in significant overhead and error sensitivity due to the dependency of merge flag encoding on the size of the merging candidate list, leading to inefficient bit stream parsing and vulnerability to errors.
Innovation Solution
Decouple the encoding of the merge flag from the size of the merging candidate list by always encoding it for each inter-predicted PU that is not using skip mode, ensuring the merging candidate list is never empty and adding a zero motion vector merging candidate if necessary, thus making bit stream parsing independent of the candidate list construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If merge flag encoding is dependent on the size of the merging candidate list, then coding efficiency can be optimized based on available candidates, but bit stream parsing becomes error-sensitive and overhead increases
Solution Approach 1:
The patent segments the merge flag encoding process into two independent parts: (1) always encoding the merge flag regardless of candidate list size, and (2) conditionally encoding merge index only when merge mode is selected and candidate list is non-empty. This segmentation isolates the error-prone dependency, making the flag encoding reliable while preserving coding efficiency through conditional index encoding.
Solution Approach 2:
The patent applies preliminary action by always encoding the merge flag before determining the final merge mode outcome. This ensures that the decoder receives unambiguous signaling about merge mode intent regardless of subsequent candidate list construction results, preventing error propagation and enabling reliable parsing independent of candidate availability.
2Adaptability or versatility
If the merging candidate list can be empty, then coding flexibility is maintained, but bit stream parsing becomes vulnerable to errors and overhead increases
Solution Approach 1:
The patent provides beforehand cushioning by ensuring the merge flag is always encoded, creating a protective layer that cushions against the potential harm of empty candidate lists. This preliminary encoding ensures that even if the candidate list turns out to be empty during decoding, the parser has already received definitive merge flag information, preventing error vulnerability and simplifying the parsing logic.
3Loss of energy
If merge mode reduces coding overhead by inheriting motion vectors from neighboring PUs, then compression efficiency improves, but the system becomes more sensitive to errors in candidate selection
Solution Approach 1:
The patent extracts the error-sensitive dependency from the merge mode encoding process by separating the merge flag encoding (always performed) from the merge index encoding (conditionally performed only when candidates exist). This extraction removes the harmful dependency relationship, allowing merge mode to maintain its overhead-reduction benefit while eliminating the error sensitivity caused by candidate list size variations.
Data Source
AI summary
Methods and apparatus for parsing friendly and error resilient merge flag coding in video coding are provided. In some methods, in contrast to merging candidate list size dependent coding of the merge flag in the prior art, a merge flag is always encoded in the encoded bit stream for each inter-predicted prediction unit (PU) that is not encoded using skip mode. In some methods, in contrast to the prior art that allowed the merging candidate list to be empty, one or more zero motion vector merging candidates formatted according to the prediction type of the slice containing a PU are added to the merging candidate list if needed to ensure that the list is not empty and/or to ensure that the list contains a maximum number of merging candidates.