Robust DTMF detection in an unreliable voice-over-IP (VoIP) environment

Abstract

A method to discriminate a signal as a DTMF digit is operative in a service provider having a VoIP-based media server. The media server accepts both in-band DTMF and RTP telephone events. A digit detection module receives as input a data stream that may include one or more DTMF digits. The module processes the input data stream and provides, as output, an indication of what digit(s) have been detected and from what source (e.g., in-band audio, an RTP 2833 telephone event, of both). The output is then further processed by a discrimination algorithm to make a final digit determination. If RTP telephone events are detected, the algorithm prefers them and ignores in-band DTMF until the call ends or the media is re-negotiated. The approach detects when duplicate digits of differing types are initially received and only accepts one of them, regardless of spacing or duration.

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