Double talk, NLP and comfort noise

摘要

A state machine for attenuating the transition into and out of NLP state to reduce voice clipping and to reduce echo leak in a voice over packet signal transmission. The state machine interposes two additional transitional states between the NLP active state and the NLP inactive state to eliminate the sharp transition of NLP activity. An NLP entering state is used to gradually reduce the mixing ratio of echo and voice to attenuate the transition from passage of echo in the NLP inactive state to the suppression of echo in the NLP active state. An NLP exiting state is used to gradually increase the mixing ratio of echo and voice to attenuate the transition from suppression of echo in the NLP active state to passage of echo in the NLP inactive state. The rate of increase/decrease is determined based upon the signal parameters, including the presence of double talk.