Temporal Layer Switching Point SEI Message Signaling
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Solution Overview
Problem
Current video coding standards face challenges in accurately signaling temporal layer switching points, particularly in scalable video bit streams, leading to difficulties in decoding and switching between temporal layers, especially when the decoding of the next lower layer has not started from the beginning of the bit stream.
Innovation Solution
The introduction of a temporal layer switching point SEI message, which includes information about the delta_frame_num, currFrameNum, and targetFrameNum, allows for proper indication of where to switch between temporal layers, ensuring correct decoding by specifying the frame number difference and target layer representation, enabling seamless switching from a first temporal layer to a second temporal layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temporal layer switching points are indicated in scalable video bit streams using conventional methods, then temporal scalability is achieved, but decoding accuracy and switching reliability deteriorate when the next lower layer decoding has not started from the beginning of the bit stream
Solution Approach 1:
The patent applies preliminary action by indicating the target layer representation picture number in advance within the temporal layer switching point SEI message. This allows the decoder to know beforehand which picture in the target layer should be decoded when switching occurs, ensuring proper synchronization without requiring the lower layer to have been decoded from the beginning. The delta_frame_num parameter provides this advance information about the switching point.
2Measurement precision
If temporal layer switching is enabled without precise switching point indication, then decoding flexibility is improved, but switching precision and picture decoding accuracy deteriorate
Solution Approach 1:
The patent segments the temporal layer switching control into distinct parameters: temporal_id for layer identification, delta_frame_num for switching point offset, currFrameNum for current picture number, and targetFrameNum for target picture number. This segmentation allows precise control of switching points while maintaining manageable decoder complexity, as each parameter has a specific function in the switching process.
3Manufacturing precision
If conventional temporal scalability methods are used without enhanced switching point indication, then bit stream compatibility is maintained, but decoding accuracy at switching points deteriorates
Solution Approach 1:
The patent introduces a SEI message as an intermediary carrier that conveys temporal layer switching point information between the encoder and decoder. This SEI message contains the delta_frame_num, currFrameNum, and targetFrameNum parameters that precisely indicate switching points without altering the core video bit stream structure, thereby maintaining compatibility while improving decoding accuracy at switching points.
Data Source
AI summary
Disclosed are a system, apparatus, computer programs and methods for indicating proper temporal layer switching points for temporal scalable coding. Various embodiments provide an apparatus and method for properly indicating temporal layer switching points in a scalable video bit stream or in a scalable video file container. Using these indications, a decoder can determine where to perform temporal layer switching, after which all of the pictures at and below the desired temporal layer can be correctly decoded.