Video Transcoding Using Extracted Motion Vectors and Residuals
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Solution Overview
Problem
Current methods for transcoding video from MPEG-4 to H.264 are computationally complex, making them unsuitable for real-time applications and often result in degraded image quality.
Innovation Solution
A method and system that utilize decoded residual information, motion vectors, and block modes to selectively refine motion vectors and determine optimal transcoding block modes, reducing the number of candidate modes and improving accuracy, thereby optimizing the transcoding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If cascade transcoding approach is used to fully decode and re-encode video, then video quality is improved, but computational complexity increases significantly
Solution Approach 1:
The patent extracts and reuses specific elements (motion vectors, block modes, residual information) from the decoded MPEG-4 video stream without performing a complete decode-re-encode cycle. This selective extraction allows maintaining video quality while significantly reducing computational complexity by avoiding redundant processing of all video data.
Solution Approach 2:
The patent performs preliminary analysis of the input MPEG-4 stream to identify and extract useful information (motion vectors, block modes, residuals) before the actual transcoding process. This preliminary action enables the transcoder to make informed decisions about which H.264 modes to evaluate, reducing the overall computational burden while maintaining quality.
2Measurement precision
If H.264 rate distortion optimization is performed for all candidate encoding modes, then encoding accuracy is improved, but processing time increases
Solution Approach 1:
The patent applies rate distortion optimization selectively to only those H.264 candidate modes that are most likely to be optimal, rather than evaluating all possible modes. By using the extracted MPEG-4 information to prune the search space, the system achieves high encoding accuracy for the selected modes while significantly reducing processing time.
Solution Approach 2:
The patent changes the parameters used for mode selection by leveraging MPEG-4 block modes, motion vectors, and residual information to guide H.264 mode decisions. This parameter-based approach allows the system to focus computational resources on promising candidates, improving encoding accuracy where needed while reducing overall processing time.
3Measurement precision
If motion estimation is performed at quarter-pixel accuracy for all macroblocks, then motion compensation accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent applies quarter-pixel accuracy motion estimation selectively to specific macroblocks based on their characteristics (such as motion activity and residual energy), rather than uniformly to all macroblocks. This local quality approach ensures high motion compensation accuracy where needed while reducing computational complexity in areas with simpler characteristics.
Solution Approach 2:
The patent performs high-precision motion estimation only for a subset of macroblocks that benefit most from it, determined by analyzing MPEG-4 motion vectors and residual information. This partial application of quarter-pixel accuracy maintains motion compensation accuracy for critical regions while significantly reducing overall computational complexity.
Data Source
AI summary
A method and system for an efficient transcoding of a sequence of input images in a first format to a sequence of output images in a second format are described. The method utilizes the encoding block mode, the motion vectors and the residual information extracted during the decoding of the input image that are effectively reused to select an optimal transcoding block mode and to perform selective refinement of motion vectors. A corresponding system for video transcoding is also provided.