Arithmetic Coding Entry Points for Parallel Bitstream 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 easily parallelized, limiting decoding speed.
Innovation Solution
An encoding and decoding concept that allows for parallel decoding by providing entry point information in the bitstream, enabling multiple decoders to operate on different parts of the bitstream simultaneously, and includes an arithmetic encoder and decoder that renormalize internal parameters and use subintervals based on probability estimates to resume decoding from a predetermined point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If arithmetic decoding is performed using a sequential process (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 contains sufficient information (interval width, interval offset, bit offset) to enable independent parallel decoding without requiring sequential processing of the entire bitstream.
Solution Approach 2:
Entry point information including interval width, interval offset, and bit offset is pre-calculated and stored during encoding. This preliminary preparation enables decoders to jump directly to specific positions in the bitstream and resume decoding without reprocessing previous data, significantly improving decoding speed.
2Productivity
If multiple decoders operate in parallel on different parts of the bitstream, then decoding speed is improved, but entry point information must be provided
Solution Approach 1:
Entry point information is pre-calculated and embedded in the bitstream during the encoding phase. This includes storing interval width, interval offset, and bit offset values at specific entry points, enabling parallel decoders to resume decoding at predetermined positions without adding significant overhead to the bitstream.
Solution Approach 2:
The encoding process modifies parameters (interval width, interval offset, bit offset) at entry points to create resumption-capable states. These parameter changes enable the bitstream to be split into independently decodable segments while maintaining the ability to reconstruct the original data through parallel processing.
3Speed
If entry point information is provided for parallel decoding, then decoding speed is enhanced, but encoder complexity increases
Solution Approach 1:
The encoder pre-calculates and stores entry point information (interval width, interval offset, bit offset) during the encoding process. This preliminary computation enables the bitstream to be segmented for parallel decoding while the encoder manages the additional complexity through systematic tracking of coding states at entry points.
Solution Approach 2:
Entry point information acts as an intermediary structure that bridges the encoder and multiple parallel decoders. It contains the necessary state information (interval parameters, bit offsets) that allows decoders to synchronize with the encoding process at specific points without requiring continuous communication with the encoder.
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.