Arithmetic Coding Entry Points for Parallel CABAC 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 effectively 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 process 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

VSEngineering Contradiction Analysis

1Speed

If arithmetic decoding is performed using traditional sequential methods (CABAC), then decoding accuracy is maintained, but decoding speed is limited due to inability to parallelize

Engineering Contradiction:

Improvedecoding speedVSAvoidcoding procedure complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The bitstream is divided into multiple segments with designated entry points, allowing multiple decoders to process different segments in parallel. Each segment is independently decodable by initializing the arithmetic decoder at the entry point with appropriate coding state information, thereby enabling parallel processing while maintaining decoding accuracy.

Inventive Principle:

Principle #1Segmentation

2Productivity

If entry point information is added to enable parallel decoding, then decoding speed improves through parallel processing, but bitstream structure complexity increases

Engineering Contradiction:

Improvedecoding efficiencyVSAvoidbitstream structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

Entry point information is pre-calculated and embedded in the bitstream during the encoding phase. This preliminary action allows decoders to directly jump to specific entry points without processing the entire bitstream sequentially, enabling efficient parallel decoding while keeping the additional structure minimal and predetermined.

Inventive Principle:

Principle #10Preliminary action

3Loss of time

If multiple decoders process different parts of the bitstream simultaneously, then decoding time is reduced, but synchronization and state management become more complex

Engineering Contradiction:

Improvedecoding timeVSAvoidstate management

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The coding state information required for parallel decoding is extracted and embedded as entry point data in the bitstream. Each entry point contains the necessary interval and offset values that allow a decoder to independently initialize and process a segment without requiring complex inter-decoder synchronization or shared state management.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS12413244B2Arithmetic encoder for arithmetically encoding and arithmetic decoder for arithmetically decoding a sequence of information values, methods for arithmetically encoding and decoding a sequence of information values and computer program for implementing these methods

Publication Date: 2025.09.09 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

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.