Arithmetic Coding Context Mapping for Spectral Coefficient Compression

Solution Overview

Problem

Existing arithmetic coding methods require a large number of probability density functions (PDFs) to handle various contexts, leading to increased encoding/decoding latency and memory requirements.

Innovation Solution

The method uses preceding spectral coefficients to determine a context class, which is then mapped to a probability density function for arithmetic encoding or decoding, employing non-uniform quantization of spectral coefficients to reduce the number of contexts and PDFs needed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a large number of probability density functions are used to handle various contexts, then compression performance is improved, but encoding/decoding latency and memory requirements increase

Engineering Contradiction:

Improvecompression performanceVSAvoidencoding/decoding latency

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent merges multiple context-specific probability density functions into a single unified adaptive probability density function. Instead of maintaining separate PDFs for each context (which increases memory and processing requirements), the system dynamically adapts a single PDF to match the current context, achieving comparable compression performance with reduced complexity and latency

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The unified adaptive probability density function serves multiple contexts simultaneously, replacing the need for multiple specialized PDFs. This universal function can adapt its parameters to model different statistical characteristics of various contexts (such as different spectral coefficient patterns in audio coding), thereby achieving multi-functionality without increasing the number of stored PDFs

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Manufacturing precision

If a large number of probability density functions are used to handle various contexts, then compression performance is improved, but memory capacity requirements increase

Engineering Contradiction:

Improvecompression performanceVSAvoidmemory capacity requirements

Core Design Contradiction:

Manufacturing precisionVSQuantity of substance

Solution Approach 1:

The patent merges multiple context-specific probability density functions into a single unified adaptive probability density function. Instead of maintaining separate PDFs for each context (which increases memory and processing requirements), the system dynamically adapts a single PDF to match the current context, achieving comparable compression performance with reduced complexity and latency

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The unified adaptive PDF uses parameter changes to adapt to different contexts. Rather than storing multiple complete PDFs, the system stores a single PDF structure with adjustable parameters that can be modified based on the current context (such as context index, spectral flatness, or other features), significantly reducing memory requirements while maintaining the ability to model various statistical distributions

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If a large number of probability density functions are used to handle various contexts, then compression performance is improved, but device complexity increases

Engineering Contradiction:

Improvecompression performanceVSAvoidcomplexity of mapping from contexts to probability density functions

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent merges multiple context-specific probability density functions into a single unified adaptive probability density function. Instead of maintaining separate PDFs for each context (which increases memory and processing requirements), the system dynamically adapts a single PDF to match the current context, achieving comparable compression performance with reduced complexity and latency

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The unified adaptive PDF uses parameter changes to adapt to different contexts. Rather than storing multiple complete PDFs, the system stores a single PDF structure with adjustable parameters that can be modified based on the current context (such as context index, spectral flatness, or other features), significantly reducing memory requirements while maintaining the ability to model various statistical distributions

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12334958B2Method and device for arithmetic encoding or arithmetic decoding

Publication Date: 2025.06.17 DOLBY LABORATORIES LICENSING CORP

AI summary

The invention proposes a method and a device for arithmetic encoding of a current spectral coefficient using preceding spectral coefficients. Said preceding spectral coefficients are already encoded and both, said preceding and current spectral coefficients, are comprised in one or more quantized spectra resulting from quantizing time-frequency-transform of video, audio or speech signal sample values.Said method comprises processing the preceding spectral coefficients, using the processed preceding spectral coefficients for determining a context class being one of at least two different context classes, using the determined context class and a mapping from the at least two different context classes to at least two different probability density functions for determining the probability density function, and arithmetic encoding the current spectral coefficient based on the determined probability density function wherein processing the preceding spectral coefficients comprises non-uniformly quantizing absolutes of the preceding spectral coefficients for use in determining of the context class.