Flexible Slice Structure for HEVC Video Coding
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Solution Overview
Problem
The existing video coding standards, such as H.264, lack flexibility in slice structure, as they primarily use macroblocks of 16×16 pixels, which is inadequate for the more granular processing required by the next-generation High Efficiency Video Coding (HEVC) standard, where larger coding units like 64×64 pixels are used, leading to a need for a more flexible slice structure that can accommodate fractional coding units and finer granularities.
Innovation Solution
The implementation of a flexible slice structure in HEVC that allows slices to be partitioned into fractional largest coding units (LCUs) using a quadtree, enabling more granular video frame division and efficient communication of this structure between encoders and decoders through specific syntax elements, such as lcu_aligned_slice_flag, send_num_lcu_flag, and end_of_slice_flag, allowing for non-LCU-aligned slice partitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LCU-aligned slice structure is used in HEVC, then coding efficiency is improved through larger 64×64 pixel blocks, but slice partition granularity becomes insufficient compared to H.264 macroblock-based slices
Solution Approach 1:
The patent segments the LCU structure by introducing fractional LCUs that can be divided into smaller parts. Slice boundaries are allowed to pass through LCUs, creating fractional LCU partitions that provide finer granularity while maintaining the benefits of larger LCU blocks for coding efficiency.
Solution Approach 2:
The patent introduces dynamic slice partitioning where the slice structure can adapt between LCU-aligned and non-LCU-aligned modes. The lcu_aligned_slice_flag parameter enables flexible switching between different partitioning granularities depending on the coding requirements, making the system adaptable to various scenarios.
2Adaptability or versatility
If flexible slice structure with fractional LCUs is implemented, then slice partition granularity is improved, but device complexity increases due to additional syntax elements and processing requirements
Solution Approach 1:
The patent applies local quality by introducing flexibility only where needed. The lcu_aligned_slice_flag parameter allows the encoder to select LCU-aligned mode for regions where simplicity is preferred and non-LCU-aligned mode for regions requiring finer granularity, optimizing the balance between complexity and adaptability locally.
Solution Approach 2:
The patent creates a universal slice structure that can function in both LCU-aligned and non-LCU-aligned modes. The same basic slice framework handles both cases, with the flexibility to adapt to different partitioning requirements without requiring entirely separate processing paths, thereby managing complexity.
3Reliability
If non-LCU-aligned slice partitions are used, then error suppression performance is improved through finer granularities, but compatibility with existing standards becomes more difficult to maintain
Solution Approach 1:
The patent introduces dynamic mode selection through the lcu_aligned_slice_flag parameter, allowing the system to switch between LCU-aligned mode (for better compatibility) and non-LCU-aligned mode (for better error suppression). This dynamic adaptation enables the system to maintain compatibility with existing standards while providing enhanced error suppression when needed.
Solution Approach 2:
The lcu_aligned_slice_flag parameter acts as an intermediary that mediates between compatibility requirements and error suppression performance. By controlling this parameter, the system can select the appropriate slice partitioning mode to balance standard compatibility with improved error suppression capabilities.
Data Source
AI summary
An apparatus and method for video coding based on flexible slice structure are disclosed. In the recent high efficiency video coding (HEVC) development, the slice may contain multiple LCUs instead of macroblocks. The LCU size being considered is 64×64 pixels which is much larger than the macroblock size of 16×16 pixels. Compared with the macroblock aligned slice for H.264, the LCU-aligned slice for HEVC does not provide enough granularities for dividing video frames. Consequently, a flexible slice structure is developed where slice partition is based on smaller coding units. In the flexible slice structure, the first LCU and the last LCU of the slice are allowed to be a fractional LCU, which is derived from a whole LCU using quadtree partition. Syntax elements are also developed to enable conveyance of flexible slice structure between an encoder and a decoder efficiently.