System and method for efficiently transporting dual-tone multi-frequency/multiple frequency (DTMF/MF) tones in a telephone connection on a network-based telephone system

• US 6,259,691 B1
• Filed: 07/24/1998
• Issued: 07/10/2001
• Est. Priority Date: 07/24/1998
• Status: Expired due to Term

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Naudus, Stanley T.
• Primary Examiner(s): HSU, ALPUS
• Application Number:
  US09/122,201
• Time in Patent Office: 1,082 Days
• Field of Search: 370/352, 370/353, 370/354, 370/356, 370/389, 370/522, 370/525, 370/526, 370/401, 370/465, 379/6.27, 379/31, 379/88.16, 379/88.17, 379/88.22, 379/88.23, 379/88.24, 379/93.01, 379/93.26, 379/219, 379/220, 379/229, 379/235, 379/360, 379/361, 379/418
• US Class Current: 370/352
• CPC Class Codes: H04M 7/1295 Details of dual tone multiple frequency signalling

Abstract

A method and system in a network telephony system for transporting audio signals with lower delay when DTMF is not present. The method of transporting audio signals determines whether DTMF signals are included in the audio signal, or are likely to be transported according to the called or calling parties. A delay is imposed in the audio when DTMF signals are sensed or determined to be present as indicated by the calling party, the destination telephone number, the called party, and various other indicators. A timer may be used to trigger a reduction and elimination in the audio delay after an initial period in the call for calls in which DTMF signaling is used for an initial period of the call. The timer may also trigger the reduction and elimination in the audio delay when no DTMF signals have been received after a period of time. The system uses a DTMF detector to sense DTMF signals in the audio signal and to signal the delay generator to impose a delay in the audio stream. The delay generator may impose the delay by elongating the time between talk-spurts or by inserting fill packets in the audio stream. The delay may be removed from the audio stream when DTMF is not likely to be present.

Claims

1. In a network-based telephone system comprising a first and second telecommunications device, the first telecommunications device being operable to generate voice signals and dual-tone multi-frequency (DTMF) signals in an audio signal, the first and second telecommunications devices being connected to a packet-based network, a method for efficiently transmitting the audio signal to the second telecommunications device, the method comprising the steps of:

detecting if the audio signal includes at least one DTMF signal;

generating an audio delay when the audio signal includes the DTMF signal;

creating an audio stream using the audio signal;

transporting the audio stream without the audio delay when the audio signal does not include the DTMF signal;

when the audio stream includes the DTMF signal, creating a separate DTMF stream using the DTMF signals in the audio signal;

transporting the DTMF stream and the audio stream on the packet-based network with the audio delay; and

decoding the DTMF and audio streams from the packet-based network to create a received audio signal, and to transmit the received audio signal to the second telecommunications device.

2. The method of claim 1 further comprising the step of, prior to the step of creating the audio stream, removing the DTMF signals from the audio signal when the audio stream includes at least one DTMF signals.

3. The method of claim 2 wherein the step of detecting if the audio signal includes at least one DTMF signal comprises the steps of analyzing the audio signal for the presence of a first DTMF signal.

4. The method of claim 3 further comprising the step of in the removing step, waiting to remove the DTMF signals until the audio delay is long enough to permit detection and removal of the DTMF signals before the DTMF signals are included in the audio stream.

5. The method of claim 4 further comprising the step of permitting at least the first DTMF signal to be transported over the audio stream if the audio delay is not long enough to permit detection and removal of the DTMF signals.

6. The method of claim 5 further comprising the steps of:

detecting whether the first DTMF signal is transmitted in the audio stream before the audio delay is sufficiently long to permit detection and removal of DTMF signals; and

playing a warning message to the first telecommunications device if the first DTMF signal is transmitted in the audio stream.

7. The method of claim 1 wherein the step of detecting if the audio signal includes at least one DTMF signal comprises the steps of analyzing the audio signal for the presence of a first DTMF signal.

8. The method of claim 1 wherein the network-based telephone system includes a first gateway connected to the first telecommunications device and the packet-based network and a second gateway connected to the second telecommunications device and the packet-based network, the method further comprising the steps of:

at the first gateway, initiating a virtual call connection for communicating the audio signal by the steps of;

receiving a dialing audio signal comprising a first sequence of DTMF signals, the first sequence of digits representing a destination telephone number,

decoding the destination telephone number;

establishing a network connection to the second gateway for transporting the destination telephone number over the packet-based network; and

completing the virtual call connection at the second gateway by the steps of connecting the virtual call connection to the second telecommunications device using the destination telephone number.

9. The method of claim 8 wherein the step of detecting whether the audio signal includes the DTMF signal comprises the steps of:

determining whether the destination telephone number is used by a party that communicates using DTMF signals during an initial period of the virtual call connection by the steps of;

retrieving a destination type from the first gateway for the destination telephone number; and

indicating that the audio signal includes at least one DTMF.

10. The method of claim 9 further comprising the step of removing the audio delay when the virtual call connection has reached a duration substantially equal to the initial period.

11. The method of claim 8 further comprising the step of retrieving a calling telephone number for the first telecommunications device, wherein:

the step of determining whether the audio signal includes at least one DTMF signals during an initial period of the virtual call connection further comprises the steps of;

retrieving a destination type from the first gateway for the calling telephone number; and

indicating that the audio signal includes at least one DTMF.

12. The method of claim 11 further comprises the step of removing the audio delay when the virtual call connection has reached a duration substantially equal to the initial period.

13. The method of claim 8 wherein the step of detecting the DTMF signals comprises the steps of:

determining whether the destination telephone number is used by a supplementary service that communicates using DTMF signals by the steps of;

retrieving a destination type from the first gateway for the destination telephone number; and

indicating that the audio signal includes at least one DTMF.

14. The method of claim 1 wherein the step of transporting the DTMF stream and the audio stream with the audio delay comprises the steps of:

initiating the audio delay in the audio stream by setting the audio delay to a short delay; and

gradually increasing the audio delay until the audio delay permits detection and removal of DTMF signals from the audio signal.

15. The method of claim 1 further comprising the steps of:

monitoring the audio signal for a plurality of additional DTMF signals; and

removing the audio delay from the audio stream when no additional DTMF signals are detected for a selected time limit.

16. The method of claim 1 further comprising the steps of:

continually sensing the audio signal to detect DTMF signals while the first telecommunications device communicates the audio signal to the second telecommunications device;

tracking the audio signal to determine a no-DTMF time period during which no DTMF signals are detected; and

when the no-DTMF time period reaches a selected time limit, removing the audio delay from the audio stream.

17. A network-based telephone system for connecting a first telecommunications device and a second telecommunications device over a packet-based network, the system comprising:

a first gateway comprising;

a telephone network interface for receiving an audio signal from the first communications device via a public switched telephone network over a virtual call connection between the first and second telecommunications devices;

a dual-tone multi-frequency (DTMF) and audio controller for detecting a DTMF signal in the audio signal, for removing the DTMF signal from the audio signal and for generating a delay in the audio signal;

an audio encoder for creating an audio stream for transporting the audio signals over the packet-based network; and

a network interface for converting the audio stream into an audio session and transporting the audio stream over the packet-based network; and

a second gateway for receiving the audio sessions, the second gateway being communicably connected to the second communications device via a second telephone network interface, the second gateway being operable to translate the audio session into a received audio signal and to transmit the received audio signal to the second communications device.

18. The system of claim 17 wherein the first gateway further comprises a DTMF decoder for creating a DTMF stream and wherein the network interface converts the DTMF stream into a DTMF session for transporting the DTMF stream over the packet-based network.

19. The system of claim 17 wherein the DTMF/audio controller comprises a DTMF detector for detecting the DTMF signals.

20. The system of claim 17 wherein the DTMF/audio controller comprises a variable delay generator for imposing the delay on the audio signal when the DTMF signal is detected in the audio signal.

21. The system of claim 18 wherein the second gateway further comprises:

a network receiver for receiving the audio and DTMF sessions from the packet-based network and for creating a received audio stream from the audio session and a received DTMF stream from the DTMF session;

a DTMF/audio multiplexer for integrating the DTMF stream to the audio stream to a received audio signal; and

a receiver telephone network interface for transmitting the received audio signal to the second communications device.

22. The system of claim 17 wherein the first gateway further comprises:

a timer for timing time periods after the detection of DTMF signals; and

a delay eliminator for removing the delay when one of the time periods reaches a selected time limit.

23. A network-based telephone system for connecting a first telecommunications device and a second telecommunications device over a packet-based network, the system comprising:

a first gateway comprising;

a telephone network interface for receiving an audio signal from the first communications device via a public switched telephone network;

a call process driver for creating a virtual call connection for communicating the audio signal, the call process driver comprising a prompter for prompting a user of the first telecommunications device for call setup information, the call setup information including a destination number and whether the destination number is of a type that includes DTMF signals during an initial period of the virtual call connection;

a dual-tone multi-frequency (DTMF) and audio controller for removing the DTMF signal from the audio signal and for generating a delay in the audio signal;

an audio encoder for creating an audio stream for transporting the audio signals over the packet-based network; and

a network interface for converting the audio stream into an audio session and transporting the audio stream over the packet-based network; and

a second gateway for receiving the DTMF and audio sessions, the second gateway being communicably connected to the second communications device via a second telephone network interface, the second gateway being operable to translate the audio session into a received audio signal and to transmit the received audio signal to the second communications device.

24. The system of claim 23 wherein the first gateway further comprises a DTMF decoder for creating a DTMF stream and wherein the network interface converts the DTMF stream into a DTMF session for transporting the DTMF stream over the packet-based network.

25. The system of claim 23 wherein the DTMF/audio controller comprises a DTMF detector for detecting the DTMF signals.

26. The system of claim 23 wherein the DTMF/audio controller comprises a variable delay generator for imposing the delay on the audio signal when the call process driver determines that the destination number uses DTMF signals.

27. The system of claim 24 wherein the second gateway further comprises:

a network receiver for receiving the audio and DTMF sessions from the packet-based network and for creating a received audio stream from the audio session and a received DTMF stream from the DTMF session;

a DTMF/audio multiplexer for integrating the DTMF stream to the audio stream to a received audio signal; and

a receiver telephone network interface for transmitting the received audio signal to the second communications device.

28. The system of claim 23 wherein the first gateway further comprises:

a timer for providing a duration of the virtual call connection; and

a delay eliminator for removing the delay when the duration of the virtual call connection has reached the initial period.

29. A network-based telephone system for connecting a first telecommunications device and a second telecommunications device over a packet-based network, the system comprising:

a first gateway comprising;

a telephone network interface for receiving an audio signal from the first communications device via a public switched telephone network;

a call process driver for creating a virtual call connection for communicating the audio signal, the call process driver comprising a prompter for prompting a user of the first telecommunications device for call setup information, the call setup information including a calling party number and whether the calling party number is of a type that includes DTMF signals during an initial period of the virtual call connection;

a dual-tone multi-frequency (DTMF) and audio controller for removing the DTMF signal from the audio signal and for generating a delay in the audio signal;

an audio encoder for creating an audio stream for transporting the audio signals over the packet-based network; and

a network interface for converting the audio stream into an audio session and transporting the audio stream over the packet-based network; and

a second gateway for receiving the audio sessions, the second gateway being communicably connected to the second communications device via a second telephone network interface, the second gateway being operable to translate the audio sessions into a received audio signal and to transmit the received audio signal to the second communications device.

30. The system of claim 29 wherein the first gateway further comprises a DTMF decoder for creating a DTMF stream and wherein the network interface converts the DTMF stream into a DTMF session for transporting the DTMF stream over the packet-based network.

31. The system of claim 29 wherein the DTMF/audio controller comprises a DTMF detector for detecting the DTMF signals.

32. The system of claim 29 wherein the DTMF/audio controller comprises a variable delay generator for imposing the delay on the audio signal when the call process driver determines that the calling party uses DTMF signals.

33. The system of claim 30 wherein the second gateway further comprises:

a network receiver for receiving the audio and DTMF sessions from the packet-based network and for creating a received audio stream from the audio session and a received DTMF stream from the DTMF session;

a DTMF/audio multiplexer for integrating the DTMF stream to the audio stream to a received audio signal; and

a receiver telephone network interface for transmitting the received audio signal to the second communications device.

34. The system of claim 29 wherein the first gateway further comprises:

a timer for providing a duration of the virtual call connection; and

a delay eliminator for removing the delay when the duration of the virtual call connection has reached the initial period.