Packet loss concealment using audio morphing

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Presented By:
Franck Bouteille¹
Pascal Scalart²
Balazs Kövesi²

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Motivation


In packet data networks, excess traffic leads to delays or loss in delivery of information. In voice communication, long delays are intolerable and network delay budgets have strong influence on the design of packet voice systems.
To increase the tolerance of packet voice systems to lost packets some techniques have been developed.
These techniques do not use the a posteriori information of the next packet that indicates and detects the lost of one or several frames.
However those techniques are not adapted for long lost periods (>15ms) because of the non long-term stationnarity of speech signal.
This a posteriori information is generally available because of the playout buffer management and real time network protocol.
The technique proposed uses the knowledge of the frame received after the last lost one, the models of the last received frames, and a model interpolation to synthesized the missing signal.



Outline


Introduction
Morphing audio principle
Voiced / Unvoiced strategy
Modelisation and Interpolation
Blocks concatenation and smoothing
Some results of concealed signal
Comparisons and performances
Configuration
Results
Conclusion


Comparisons and performances



Ten subjects were participating to an informal test: they were asked to listen to coded speech signals that have been corrected by different concealment techniques


Configuration


Two speech coders (G.711 and G.723.1) were independently tested, The size frame is 30ms;

Five concealment techniques : Previous Frame Copy: PFC, double Sided Periodic Substitution: DSPS1, ITU-T recommended technique defined for each specific coder: G.711 and G.723.1, GFEC technique2 and Audio Morphing;

Two series of rate were defined: 5 % and 10 %. The losses can appear by burst, but are usually isolated ;

The number of sentences was 15 (8 female and 7 male speech files)


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http://portal.etsistq/workshop2003/prese...tarion.ppt