Image Decoding Apparatus Reducing WPP Processing Delay
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Solution Overview
Problem
Wavefront Parallel Processing (WPP) in video coding and decoding experiences increased delay with larger numbers of Coding Tree Units (CTU) rows and CTU sizes, leading to inefficiencies in processing and parallelism.
Innovation Solution
An image decoding apparatus that decodes CTU rows sequentially from top, using decoded data from a fixed number of CTUs ahead, including a prediction image generation unit to generate prediction images and a decoder to process CTUs based on information from preceding CTUs, reducing delay by allowing earlier initiation of intra and inter prediction processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Wavefront Parallel Processing (WPP) is used to decode CTU rows sequentially, then parallel processing capability is improved, but processing delay increases as the number of CTU rows and CTU size increases
Solution Approach 1:
The patent applies preliminary action by allowing the prediction image generation unit to start generating prediction images for the current CTU row using decoded data from a fixed number of CTUs ahead in the previous row, rather than waiting for complete decoding of the entire previous row. This enables earlier initiation of prediction processes, reducing processing delay while maintaining parallel processing efficiency.
2Loss of time
If a fixed number of CTUs ahead are used for prediction, then processing delay is reduced, but the complexity of managing decoded data increases
Solution Approach 1:
The patent applies segmentation by dividing the picture into multiple CTU rows and further segmenting the reference data requirement into a fixed number of CTUs ahead. This structured segmentation simplifies data management by defining clear boundaries and access patterns for the prediction image generation unit, making it easier to manage the decoded data buffer and access requirements.
Data Source
AI summary
Delay based on WPP processing is reduced. An image decoding apparatus (31) includes: a prediction image generation unit (308) by using decoded data from a first position to a second position, the first position being, in a CTU row immediately above a CTU row including a target CTU, identical to a position of the target CTU, the second position being a position one CTU forward relative to the first position; and an entropy decoding unit (301) that performs decoding of the target CTU by using the decoded data from the first position to the second position, the first position being, in the CTU row immediately above the CTU row including the target CTU, identical to the position of the target CTU, the second position being a position one CTU forward relative to the first position.