Multi-pass Video Encoding for Motion Estimation
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Solution Overview
Problem
Conventional video compression techniques face inefficiencies due to the distance in timing between the motion estimation stage and the reconstruction stage, leading to visual artifacts and reduced compression efficiency, as the encoder cannot utilize desirable data for motion estimation.
Innovation Solution
A multi-pass encoding method is implemented, where a first pass encodes and stores predictor pixels, and a second pass re-encodes the data using these stored predictor pixels, allowing for improved intra-prediction mode selection and reduced visual artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multi-stage pipeline is used for video encoding, then processing speed and performance are improved, but the timing distance between motion estimation and reconstruction stages increases, causing loss of useful data for motion estimation
Solution Approach 1:
The encoding process is divided into multiple passes (first pass for motion estimation, second pass for reconstruction) rather than a single sequential stage. This segmentation allows motion estimation to access and utilize reconstructed data from the first pass during the second pass, resolving the timing conflict while maintaining overall processing efficiency.
2Loss of time
If conventional single-pass encoding is used, then processing time is reduced, but compression efficiency and visual quality deteriorate due to inability to use reconstructed data for motion estimation
Solution Approach 1:
The first pass performs preliminary encoding and reconstruction of the frame before the second pass uses this reconstructed data for improved motion estimation. This preliminary action ensures that useful data is available in advance for the subsequent motion estimation stage, improving compression efficiency without excessive time loss.
Solution Approach 2:
The multi-pass approach maintains continuous utilization of reconstructed data throughout the encoding process. The first pass generates reconstructed data that is immediately available for the second pass, ensuring continuous useful action rather than idle waiting periods, thus improving compression efficiency while managing processing time.
Data Source
AI summary
In accordance with aspects of the disclosure, devices and methods are provided for receiving uncompressed image data and performing multi-pass encoding of the uncompressed image data including encoding a frame of the uncompressed image data in a first pass, storing predictor pixels from the encoded frame in a memory, and re-encoding the frame of the uncompressed image data in a second pass using the stored predictor pixels from the first pass.