Video Encoding Mode Selection Using Bidirectional Prediction Costs
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Solution Overview
Problem
The high computation complexity and efficiency issues in real-time video encoding on mobile platforms due to the complexity of the H.264/AVC standard, particularly in selecting optimal prediction modes for B frames, hinder effective video transmission and compression.
Innovation Solution
A video encoding method that simplifies the mode selection process by computing and comparing mode costs after motion compensation using bidirectional, forward, and backward prediction motion vectors, selecting the mode with the smallest cost as the optimal prediction direction, and limiting the process to only the Skip and Direct prediction modes, reducing unnecessary computations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If H.264/AVC standard is used for video encoding, then encoding efficiency and image quality are improved, but computation complexity increases
Solution Approach 1:
The macroblock is divided into four 8x8 luma blocks and two 8x4 or 4x8 chroma blocks. Each block can be independently processed with its own prediction mode selection, allowing the complex encoding process to be broken down into manageable segments that can be processed in parallel
Solution Approach 2:
The patent performs mode cost computation for all nine prediction modes (three intra-mode and six inter-mode) for each block, even though in practice not all modes will be selected. This exhaustive approach ensures optimal quality but increases computation, which is then managed through the segmentation principle
2Manufacturing precision
If multiple prediction modes are computed and compared for B frame encoding, then encoding quality is improved, but computation complexity and time increase
Solution Approach 1:
The prediction mode selection is segmented into independent evaluations for each block type (luma and chroma) and each prediction direction (intra and inter). This allows the system to compute costs for multiple modes in parallel across different blocks rather than sequentially evaluating all modes for one block before moving to the next
Solution Approach 2:
The patent pre-computes motion compensation results and mode costs for all candidate prediction modes before final mode selection. By preparing these calculations in advance, the system avoids repeated computations during the mode decision phase, reducing overall encoding time
3Measurement precision
If motion estimation and mode selection are performed for each macroblock, then prediction accuracy is improved, but computation complexity increases
Solution Approach 1:
The macroblock prediction process is segmented into separate intra-mode prediction and inter-mode prediction pathways. Each pathway handles specific prediction types with dedicated motion compensation logic, allowing the system to optimize each segment independently rather than processing all prediction types uniformly across all blocks
Solution Approach 2:
Different prediction modes and computation strategies are applied to different blocks based on local characteristics. Luma blocks use 8x8 processing while chroma blocks use 8x4 or 4x8 processing. Motion compensation parameters are optimized locally for each block based on its specific content and motion characteristics
Data Source
AI summary
The present application provides a video encoding method that includes setting frame types for a video sequence; obtaining a B frame; determining whether a current macroblock of the B frame satisfies a Direct prediction mode, and if yes determining whether the current macroblock satisfies a Skip prediction mode; if the current macroblock does not meet either mode, computing at least one of a mode cost after performing motion compensation on the current macroblock using two bidirectional prediction motion vectors obtained in the Direct prediction mode; a mode cost after performing motion compensation on the current macroblock using a forward prediction motion vector obtained in the Direct prediction mode; and a mode cost after performing motion compensation on the current macroblock using a backward prediction motion vector obtained in the Direct prediction mode; and selecting a mode with a smallest cost as an optimal prediction direction to encode the current macroblock.