Vector Quantizer Mode Switching for Frame Erasure Resilience

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Solution Overview

Problem

Audio codecs using predictive quantization for speech signals can introduce annoying artefacts during frame erasure events due to desynchronization of predictor memories between the encoder and decoder, leading to undesirable effects in the decoded audio signal.

Innovation Solution

A method and apparatus that dynamically switch between predictive and non-predictive modes of operation for a vector quantiser based on distortion measures and frame error concealment processes, determining the optimal mode for subsequent audio frames to minimize artefacts and maintain signal quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If predictive mode is used for vector quantization, then coding efficiency is improved, but artefacts occur during frame erasure events

Engineering Contradiction:

Improvecoding efficiencyVSAvoidartefacts in decoded signal

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system dynamically switches between predictive and non-predictive modes based on channel conditions. The vector quantizer adapts its operation mode in real-time, being predictive during good conditions and non-predictive during erasure events, thereby optimizing both coding efficiency and artefact reduction across varying transmission scenarios

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the operational parameter of the vector quantizer from a fixed predictive mode to a variable mode that can switch between predictive and non-predictive operations. This parameter change allows the system to adapt to channel erasures by disabling prediction when reliability is low, thus eliminating artefacts while maintaining efficiency during reliable transmission

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If predictive quantization is used, then bit rate efficiency is improved, but desynchronization between encoder and decoder occurs during frame erasure

Engineering Contradiction:

Improvebit rate efficiencyVSAvoidsynchronization between encoder and decoder

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The system uses feedback about channel conditions and frame erasure detection to control the operational mode of the vector quantizer. When frame erasures are detected, the system feeds back this information to switch to non-predictive mode, ensuring encoder and decoder remain synchronized by preventing divergence caused by unequal error recovery

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The invention prepares for potential frame erasures by having a pre-configured non-predictive mode ready to activate. This beforehand cushioning ensures that when erasures occur, the system can immediately switch to a safe mode that prevents desynchronization, rather than attempting to recover from already-diverged predictor states

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS10109287B2Method and apparatus for resilient vector quantization

Publication Date: 2018.10.23 NOKIA TECHNOLOGIES OY

AI summary

It is inter alia disclosed to quantize a vector of a plurality of coefficients using a predictive mode of operation of a vector quantizer, wherein the vector quantizer can operate in either a predictive mode of operation or a non-predictive mode of operation, determine a vector of a plurality of recovered coefficients; compare the vector of the plurality of coefficients to the vector of the plurality of recovered coefficients; and determine the mode of operation of the vector quantizer for a vector of a plurality of coefficients associated with a subsequent frame of audio samples, wherein the mode of operation is dependent on the comparison.