Video Encoder Block Size Selection via Decision Tree
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Solution Overview
Problem
Evaluating different block sizes for video encoding in HEVC is costly, particularly when fast encoding is required, as it significantly increases encoding time due to the need to assess various transform and prediction unit sizes.
Innovation Solution
A method and encoder that quickly choose block sizes by comparing predefined combinations of block sizes, focusing on the most efficient options first, such as comparing the first combination against the second and then against the third, to select the best option based on distortion measures, thereby reducing the need for full evaluations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If different block sizes are evaluated to improve compression efficiency, then compression efficiency is improved, but encoding time increases significantly
Solution Approach 1:
The patent segments the evaluation process by dividing block size selection into multiple stages: initial selection of a limited set of candidate block sizes, preliminary evaluation of these candidates, and final selection based on distortion measures. This segmentation avoids evaluating all possible block sizes while still achieving good compression efficiency.
Solution Approach 2:
The patent applies partial action by evaluating only a subset of block size options rather than all possible sizes. It performs sufficient evaluation to achieve good compression results without the excessive action of exhaustively testing every block size combination, thereby reducing encoding time while maintaining effectiveness.
2Manufacturing precision
If full evaluation of all block size combinations is performed to achieve optimal compression, then compression quality is improved, but device complexity increases
Solution Approach 1:
The encoder complexity is reduced by segmenting the block size selection into manageable stages with predetermined candidate sets. This avoids the need for a complex exhaustive evaluation system while still achieving optimal compression quality through structured, multi-stage decision-making.
Solution Approach 2:
The patent changes the parameter of block size evaluation by using predetermined candidate sets and distortion measures instead of exhaustive evaluation. This parameter change simplifies the encoder's decision-making process while maintaining the ability to achieve high compression quality.
3Productivity
If multiple transform unit sizes are evaluated to improve compression efficiency, then compression efficiency is improved, but encoding time increases
Solution Approach 1:
The patent applies partial action by evaluating only necessary transform unit size options based on the selected block size and content characteristics. This avoids excessive evaluation of all possible transform sizes while achieving sufficient compression efficiency for practical applications.
Data Source
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AI summary
The embodiments relate to an encoder for encoding a bitstream representing a sequence of pictures of a video stream. The encoder is operative to divide the pictures into blocks of different types, such as coding units CUs, prediction units PUs, and transform units TUs, which are associated with each other. Two sizes are possible for the blocks and the possible combinations are restricted to three cases: 1) all blocks are of large size, 2) the CUs and PUs have large size, while associated TUs have small size, 3) all blocks are of small size. The possible combinations are defined for a part of a picture and compared against each other using a decision tree. In this way an advantageous block size configuration for encoding the bitstream is determined at a reduced computational cost.