VoIP Media Server DTMF Discrimination via RTP Priority
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Solution Overview
Problem
In VoIP-based communication systems, service providers face challenges in accurately distinguishing and processing DTMF digits due to inconsistencies in signaling methods between TDM and VoIP carriers, leading to incorrect digit detection and handling of duplicate signals.
Innovation Solution
A method is implemented in a VoIP-based media server using a digit detection module and filtering algorithm to differentiate between in-band DTMF and RTP telephone events, prioritizing RTP events and discarding duplicate or inconsistent in-band signals, ensuring accurate digit detection and handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If both in-band DTMF and RTP telephone events are accepted regardless of carrier negotiation, then the system can handle multiple signaling methods, but duplicate or mismatched signals cause incorrect digit detection
Solution Approach 1:
The patent applies local quality by treating in-band DTMF and RTP telephone events differently based on their source and characteristics. The filtering module examines the specific properties of each signal type and applies appropriate filtering rules: in-band signals are filtered when RTP events are present, while RTP events are filtered when in-band signals are detected, ensuring each signaling method is handled with its own specific rules to prevent duplication
Solution Approach 2:
The patent implements feedback through the filtering module that continuously monitors incoming DTMF signals and adjusts acceptance based on previously detected signal types. When an in-band DTMF is detected, the system checks for corresponding RTP events and vice versa, using this feedback information to determine whether to accept or discard the current signal, thereby maintaining digit detection accuracy
2Reliability
If RTP telephone events are preferred over in-band DTMF, then digit detection reliability improves, but compatibility with TDM systems that use in-band signaling decreases
Solution Approach 1:
The patent achieves universality by creating a filtering module that handles both in-band DTMF and RTP telephone events within a single unified system. The module can process and filter both signal types according to their respective characteristics, making the system universally compatible with different carrier types (both TDM and VoIP) while maintaining reliable digit detection through preferential treatment of RTP events when available
Data Source
AI summary
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.