Digital coding of covert audio for monitoring and storage
Michael Mason, Sridha Sridharan, Robert Prandolini · 2003
This paper offers an overview of the requirements of digital covert audio acquisition (DCAA) and presents a codec that provides both real-time monitoring and efficient on-site storage. The codec incorporates an M-band discrete wavelet transform (DWT) subband decomposition with lattice vector quantisation (LVQ) of the wavelet coefficients to compress high quality covert audio to less then 32 kbps. Both objective quality measures for the monitoring channel and average growth rate of the on-site storage are presented to demonstrate that the proposed codec achieves the requirements of a covert audio acquisition system.