Video Coding CPB Parameter Selection for Random Access Points
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Solution Overview
Problem
Existing video coding technologies face issues with overflow in coded picture buffers (CPBs) when default CPB parameters are used for random access point (RAP) pictures, such as clean random access (CRA) and broken link access (BLA) pictures, instead of the alternative set that should be selected.
Innovation Solution
A method is described where a video coding device receives a bitstream and a message indicating whether to use an alternative set of CPB parameters for CRA or BLA pictures, setting a variable to select the appropriate set of CPB parameters to prevent overflow, by setting a network abstraction layer (NAL) unit type based on the received message and variable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If default CPB parameters are used for RAP pictures, then the video coding device operates with standard parameters, but the CPB may overflow causing decoding errors
Solution Approach 1:
The patent applies preliminary action by introducing a flag in the bitstream that预先 indicates which set of CPB parameters should be used for RAP pictures. This allows the decoder to select the correct parameters before decoding the RAP picture, preventing CPB overflow without adding complex runtime decision logic. The parameter selection is determined in advance through the flag mechanism.
2Reliability
If alternative set of CPB parameters is selected for RAP pictures, then CPB overflow is prevented, but the device must implement complex parameter selection logic
Solution Approach 1:
The patent applies self-service by having the bitstream itself carry the information (flag) needed to select the correct CPB parameters. The decoder reads the flag from the bitstream and automatically selects the appropriate parameter set without requiring external control or complex decision logic. The system serves itself by encoding the parameter selection information directly in the data stream.
3Reliability
If a flag is added to the bitstream to indicate CPB parameter set, then correct parameter selection is enabled, but the bitstream size increases
Solution Approach 1:
The patent applies segmentation by dividing the CPB parameters into two distinct sets (default and alternative) and using a single-bit flag to indicate which set to use. This segmentation allows the system to maintain separate parameter configurations without duplicating entire parameter sets, thereby minimizing the additional bitstream overhead to just one flag bit while ensuring accurate parameter selection.
Data Source
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AI summary
This disclosure describes techniques for selection of coded picture buffer (CPB) parameters used to define a CPB for a video coding device for clean random access (CRA) pictures and broken link access (BLA) pictures in a video bitstream. A video coding device receives a bitstream including one or more CRA pictures or BLA pictures, and also receives a message indicating whether to use an alternative set of CPB parameters for at least one of the CRA pictures or BLA pictures. The message may be received from an external means, such as a processing means included in a streaming server or network entity. The video coding device sets a variable defined to indicate the set of CPB parameters for a given one of the pictures based on the received message, and selects the set of CPB parameters for the given one of the pictures based on the variable for the picture.