Intra Prediction Mode Selection in Video Coding Pipelines
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Solution Overview
Problem
In the HEVC video coding system, determining the optimum intra prediction mode is challenging when intra and inter prediction blocks coexist within a coding tree unit, as the intra prediction modes of neighboring blocks may be replaced during the pipeline process, making it difficult to calculate the necessary code amount for selecting the optimal intra prediction mode.
Innovation Solution
An image coding apparatus that selects the intra prediction mode by considering neighboring blocks coded with inter prediction, using a selecting unit to choose the appropriate mode from available intra prediction modes for intra prediction coding, even when inter prediction coding is applicable to the frame containing the target coding block.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a pipeline process is performed in units of coding block to determine intra prediction modes, then processing speed is improved, but the intra prediction modes of neighboring blocks may not be settled when the target block is processed, making it impossible to calculate the code amount necessary for selecting the optimum intra prediction mode
Solution Approach 1:
The patent applies preliminary action by performing preliminary determination of intra prediction modes for all blocks in the CTU before the inter/intra determination process. This preliminary determination ensures that neighboring block modes are already settled when the target block is processed, enabling accurate code amount calculation while maintaining pipeline processing speed. The preliminary determined modes are stored and referenced during subsequent processing stages.
2Productivity
If the intra prediction mode of a certain block is determined in the intra prediction mode determining process, then the mode is selected, but it may be replaced by inter prediction mode in later pipeline-stage processes, making it impossible to distinguish whether neighboring blocks are replaced
Solution Approach 1:
The patent applies feedback by implementing a mechanism where the determination result (intra or inter prediction mode) of each block is fed back and stored. During the inter/intra determination process, the previously determined intra prediction modes are referenced, and the final determination results are fed back to update the mode information. This feedback loop ensures that the final prediction modes (whether intra or inter) are accurately tracked throughout the pipeline process, preventing information loss about mode replacements.
3Manufacturing precision
If five kinds of intra prediction block sizes and 35 intra prediction modes are provided in HEVC, then coding efficiency is improved, but a large operation amount is necessary to select an optimum combination
Solution Approach 1:
The patent applies preliminary action by pre-determining the intra prediction modes for all blocks in the CTU before the inter/intra determination process. This preliminary determination of intra modes eliminates the need to recalculate or reconsider intra modes during later stages, significantly reducing the operation amount required for mode selection while maintaining the ability to evaluate all 35 intra prediction modes and 5 block sizes for optimal coding precision.
Data Source
AI summary
A selecting unit selects, from plural intra prediction modes, the intra prediction mode to be used for intra prediction coding of a target coding block. A coding unit performs the intra prediction coding to a frame constituted by plural blocks in units of the block, in the intra prediction mode selected by the selecting unit. Further, in a case where inter prediction coding can be used as a coding system of the frame in which the target coding block is included, the selecting unit considers the neighboring blocks of the target coding block to have been coded with the inter prediction and selects the intra prediction mode to be used for the intra prediction coding of the target coding block from among the plural intra prediction modes.