Conditional Reference Picture List Signaling for Lower Bit Rates
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Solution Overview
Problem
Signaling of reference picture list (RPL) modification information in video codecs consumes a significant amount of bits and is inefficient.
Innovation Solution
Implement conditional signaling of RPL modification information based on evaluation conditions, allowing for the construction of default RPLs when unmodified and explicit signaling of modified RPLs when necessary, with adjustments such as adding, removing, or reordering reference pictures in a fine-grained manner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If explicit signaling of RPL modification information is performed, then the precision of reference picture list management is improved, but the bit rate consumption increases significantly
Solution Approach 1:
The patent extracts and removes redundant RPL modification information from the bitstream. By identifying that many RPL modifications follow predictable patterns or can be inferred from existing data, the invention selectively excludes unnecessary signaling elements, keeping only the essential modification information that cannot be deduced otherwise.
Solution Approach 2:
Instead of explicitly signaling all RPL modifications as traditionally done, the patent inverts the approach by signaling only when modifications occur and allowing the decoder to infer default states. This inversion reduces signaling overhead by leveraging the fact that no modification is the common case, and modifications are the exception that needs explicit indication.
2Quantity of substance
If conditional signaling is implemented, then the bit rate efficiency is improved, but the decoder complexity increases
Solution Approach 1:
The patent applies preliminary action by having the encoder pre-determine and signal only the necessary RPL modification information based on actual changes. The decoder uses this pre-signal information to reconstruct RPLs without needing to perform complex analysis, as the essential modification data is already provided in an optimized format.
Solution Approach 2:
The decoder leverages self-service by using the signaled modification information combined with its own inference capabilities to reconstruct RPLs. The system allows the decoder to serve itself by inferring unmodified RPL entries from context and existing reference picture sets, reducing the need for exhaustive explicit signaling.
3Adaptability or versatility
If fine-grained RPL modifications are signaled, then the adaptability of reference picture management is improved, but the signaling overhead increases
Solution Approach 1:
The patent segments RPL modification signaling into distinct categories: explicit modifications (when changes occur) and inferred modifications (when no changes occur). This segmentation allows the system to maintain fine-grained control over individual reference pictures while avoiding the overhead of signaling every possible modification, as only relevant segments are transmitted.
Solution Approach 2:
The patent changes the parameter representation by using conditional signaling flags and inference-based reconstruction. Instead of transmitting complete RPL modification sets, the system uses parameter changes only when necessary (when modifications occur), allowing the decoder to infer default parameter states from context and existing reference picture configurations.
Data Source
AI summary
Innovations in signaling of reference picture list (“RPL”) modification information. For example, a video encoder evaluates a condition that depends at least in part on a variable indicating a number of total reference pictures. Depending on the results of the evaluation, the encoder signals in a bitstream a flag that indicates whether an RPL is modified according to syntax elements explicitly signaled in the bitstream. A video decoder evaluates the condition and, depending on results of the evaluation, parses from a bitstream a flag that indicates whether an RPL is modified according to syntax elements explicitly signaled in the bitstream. The condition can be evaluated as part of processing for an RPL modification structure that includes the flag, or as part of processing for a slice header. The encoder and decoder can also evaluate other conditions that affect syntax elements for list entries of the RPL modification information.