Merge Flag Coding for Error-Resilient Video Bitstream Parsing
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Solution Overview
Problem
The existing merge mode in HEVC video coding standards has high overhead and error sensitivity due to conditional encoding of the merge flag, which depends 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, and ensure the merging candidate list is never empty by adding a zero motion vector candidate if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the merge flag is conditionally encoded based on the size of the merging candidate list, then the coding overhead is reduced when the list is empty, but the bit stream parsing becomes error-sensitive and inefficient
Solution Approach 1:
The patent segments the merge flag encoding into two distinct parts: a reserved bit position that is always present in the bit stream, and the actual merge mode information. This segmentation ensures that the bit stream structure remains consistent even when the merging candidate list is empty, eliminating error sensitivity while maintaining coding efficiency through conditional information placement.
Solution Approach 2:
The patent performs preliminary action by reserving a specific bit position for the merge flag before the merging candidate list is constructed or determined to be empty. This advance reservation ensures that the bit stream parsing can proceed without errors regardless of the list size, as the expected data structure is already in place.
2Reliability
If the merge flag is always encoded for each inter-predicted PU, then error resilience and parsing consistency are improved, but the coding overhead increases
Solution Approach 1:
The patent applies local quality by making the merge flag encoding behavior context-dependent rather than uniformly applied. The reserved bit position is always present, but the actual merge mode information is only encoded when the merging candidate list is not empty, optimizing the balance between reliability and overhead for each specific case.
Solution Approach 2:
The patent changes the parameter of merge flag encoding from a binary state (encoded or not encoded) to a three-state system: reserved bit always present, merge mode information encoded conditionally based on list size. This parameter change enables consistent parsing structure while avoiding unnecessary overhead.
3Adaptability or versatility
If the merging candidate list can be empty, then coding flexibility is maintained, but the merge mode operation becomes undefined and error-prone
Solution Approach 1:
The patent provides beforehand cushioning by preparing a default merging candidate (zero motion vector candidate) in advance when the merging candidate list would otherwise be empty. This default candidate ensures that the merge mode operation always has valid data to work with, preventing undefined behavior and errors while maintaining coding flexibility.
Solution Approach 2:
The patent uses a simple zero motion vector candidate as a disposable fallback when the merging candidate list is empty. This minimal object provides just enough functionality to prevent errors without the complexity of more sophisticated solutions, and is only used when necessary.
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.