This paper presents a novel mechanism for dynamically adapting the quality of congestion controlled Voice Over IP (VoIP) applications on the internet in real time. The system uses our proposed variable bit rate speech codec called Speex, which can dynamically adjust the encoding bit rate (and hence the speech quality) based on both the feedback information about the network congestion and the instantaneous speech properties. Our extensive NS2 simulation results prove that the proposed system

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... eed provides highest quality speech while maximising the bandwidth utilisation and reducing the network congestion.