Arithmetic Coded Bitstream Segmentation for Parallel Decoding
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Solution Overview
Problem
Existing arithmetic decoding processes, such as context-based adaptive binary arithmetic coding (CABAC), are highly sequential and cannot be parallelized, limiting decoding speed.
Innovation Solution
An encoding concept that symbolizes information values into symbol strings, subdivides coding intervals based on probability estimates, and provides entry point information for parallel decoding, allowing multiple decoders to operate on different parts of a bitstream simultaneously.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If arithmetic decoding is performed using sequential processing (CABAC), then decoding accuracy is maintained, but decoding speed is limited
Solution Approach 1:
The bitstream is divided into multiple segments with designated entry points, allowing multiple decoders to process different segments simultaneously. Each segment is independently decodable by resetting the decoding state at entry points, enabling parallel processing while maintaining decoding accuracy through proper state management at segment boundaries.
Solution Approach 2:
Entry points are pre-defined and marked within the bitstream during encoding, indicating positions where decoding can be safely restarted. This preliminary structuring of the bitstream allows decoders to jump to specific positions and resume processing without requiring full sequential processing from the beginning, thereby enabling parallel decoding operations.
2Productivity
If multiple decoders operate in parallel, then decoding speed is improved, but coordination complexity increases
Solution Approach 1:
The bitstream is segmented into independent processing units with clear entry points, allowing multiple decoders to work on different segments simultaneously without interfering with each other. This segmentation naturally distributes the workload and reduces coordination overhead since each decoder operates independently on its assigned segment.
Solution Approach 2:
The decoding state and context information are copied to multiple decoder instances, each starting from a predefined entry point. This copying approach allows parallel decoders to operate with identical initial conditions tailored to their respective segments, eliminating the need for complex inter-decoder communication and synchronization.
3Speed
If entry point information is added to the bitstream, then parallel decoding is enabled, but bitstream size increases
Solution Approach 1:
Entry point markers are added only at strategically selected positions within the bitstream rather than at every possible position. This partial application of entry point information provides sufficient opportunities for parallel decoding while minimizing the overhead added to the bitstream size.
Solution Approach 2:
The entry point information is encoded using compact parameter representations that minimize the additional bits required. By optimizing the encoding of entry point positions and using efficient data structures, the overhead is kept minimal while still enabling effective parallel decoding.
Data Source
AI summary
An encoding scheme is provided for arithmetically encoding a sequence of information values into an arithmetic coded bitstream by providing the bitstream with entry point information, allowing for resuming arithmetic decoding of the bitstream from a predetermined entry point onward. A respective decoding scheme is also provided. These encoding and decoding schemes provide more efficient encoding in view of the decoding speed.