Q. Gong and P. Kabal
"Quality-Based Playout Buffering with FEC for Conversational VoIP", Proc. Interspeech (Makuhari, Japan), pp. 2402-2405, Sept. 2010.
In Voice-over-IP, buffer delay and packet loss are two main factors affecting perceived quality. A quality-based algorithm aims to seek an optimum balancing of delay versus loss. To improve perceived quality further, steps should be taken to mitigate the effects of losses due to network (missing packets) and buffer underflow (late packets) without increasing buffer delay. In this paper, we propose a quality-based playout algorithm with an FEC design based on conversational quality including calling quality and interactivity. The simulation results show our algorithm's efficiency of correcting for losses (isolated and burst) and improving perceived conversational quality.
P. Kabal, R. Rabipour, and Y. Qian
"Method and Apparatus for Extending the Bandwidth of a Speech Signal", US patent 7,734,462, June 2010.
A bandwidth extension module, and an associated method and computer-readable medium, suitable for use in artificially extending the bandwidth of a lowband speech signal. The bandwidth extension module comprises a band-pass filter configured to produce a band-pass signal from the lowband speech signal; at least one carrier frequency modulator, each carrier frequency modulator configured to pitch-synchronously modulate the band-pass signal about a respective carrier frequency, the at least one carrier frequency modulator collectively producing a highband speech signal component; a synthesis filter configured to determine a highband speech signal based on the highband speech signal component; and a summation module configured to combine the lowband speech signal with the highband speech signal to obtain a bandwidth-extended speech signal.