Adaptive Damping Factor for Audio Error Concealment
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Solution Overview
Problem
Existing audio codecs face challenges in maintaining audio quality when audio frames are lost during transmission over unreliable channels, particularly due to the use of static damping factors that lead to annoying post echo artefacts, especially in speech signals.
Innovation Solution
An error concealment unit that derives a damping factor based on the characteristics of the properly decoded audio frame preceding the lost frame, allowing for adaptive fade-out in different frequency bands to reduce post echo artefacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a static damping factor is used for fade out in error concealment, then the implementation is simple, but post echo artefacts occur especially in speech signals
Solution Approach 1:
The patent applies dynamics by transitioning from a static damping factor to a dynamic, adaptive damping factor that changes based on signal characteristics. The damping factor is adjusted according to the energy trend and spectral features of the audio signal, allowing the error concealment system to adapt its behavior to different signal types (speech, music, noise) and different loss scenarios, thereby reducing post echo artefacts while maintaining implementation feasibility
Solution Approach 2:
The patent implements parameter changes by modifying the damping factor parameter based on analyzed characteristics of the audio signal. The system calculates energy trends, spectral flatness, and other features to dynamically adjust the damping factor value, transforming it from a fixed parameter to a variable one that responds to signal conditions, thus eliminating post echo artefacts without significantly increasing complexity
2Reliability
If audio frames are requested to be resent after loss, then complete audio data can be recovered, but substantial delay and extensive buffering are required
Solution Approach 1:
The patent applies preliminary action by preparing error concealment data in advance using previously received audio frames before the actual loss occurs. The system maintains a buffer of decoded frames and pre-calculates potential concealment signals, so that when a frame is lost, the concealment can be immediately applied without waiting for retransmission, thus reducing delay while maintaining audio continuity
Solution Approach 2:
The patent introduces an intermediary error concealment mechanism that acts as a mediator between the lost audio frame and the reconstructed output. Instead of directly requesting retransmission, the system uses the intermediary concealment signal derived from adjacent frames to bridge the gap, reducing the urgency and delay associated with retransmission requests while maintaining acceptable audio quality
Data Source
AI summary
There is provided an error concealment unit, method, and computer program, for providing an error concealment audio information for concealing a loss of an audio frame in an encoded audio information. In one embodiment, the error concealment unit provides an error concealment audio information for a lost audio frame on the basis of a properly decoded audio frame preceding the lost audio frame. The error concealment unit derives a damping factor on the basis of characteristics of a decoded representation of the properly decoded audio frame preceding the lost audio frame. The error concealment unit performs a fade out using the damping factor.