Controlling the transition glitch that occurs when a gateway switches from voice over IP to voice band data

• US 7,058,066 B1
• Filed: 01/22/2004
• Issued: 06/06/2006
• Est. Priority Date: 01/22/2004
• Status: Expired due to Fees

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Garakani, Mehryar Khalili, Cutaia, Nicholas, Luong, Hanh
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): ABELSON, RONALD B
• Application Number:
  US10/763,771
• Time in Patent Office: 866 Days
• Field of Search: 370/401, 370/389, 370/392, 370/516, 370/356, 370/526, 370/352
• US Class Current: 370/401
• CPC Class Codes: H04J 3/0632 Synchronisation of packets and cells, e.g. transmission of voice via a packet network, circuit emulation service [CES] queuing arrangements in packet switching elements H04L49/90; synchronising systems for the synchronous transmission of a pulse code modulated video signal with one or more other pulse code modulated signals H04N7/56
• CPC Class Codes: H04L 12/6418 Hybrid transport

Abstract

In a gateway router the length of the play-out buffer in VBD mode is not set at a previously established value. Instead the length of the play-out buffer in VBD mode is determined by the length of the buffer in the previous audio mode. When the system switches from audio mode to VDB mode, the length of the play-out buffer in audio mode is noted. The length of the play-out buffer in VBD mode is then set equal to its length in the prior audio mode plus a dilation factor. An audio concealment algorithm (which fills in gaps caused by missed packets) is used during the transition from audio to VDB to conceal any transition glitch during the answer tone.

Claims

1. A method of operating a gateway comprising:

setting the length of the play-out buffer in a gateway when the gateway switches from audio mode to voice band data (VBD) mode by;

detecting the previous length of the play-out buffer in the previous audio mode, adding a dilation factor to said previous length to obtain a new length, and setting said play-out buffer to said new length.

3. The method recited in claim 1 wherein the length of said play-out buffer in audio mode is set adaptively.

5. The method recited in claim 1 wherein audio concealment techniques are used to fill any gaps caused by the change in length of the play-out buffer.

7. The method recited in claim 1 wherein said switch from audio mode to VBD mode occurs when a first client places a call to a second client and said second client generates an answer tone.

9. The method recited in claim 3 wherein audio concealment techniques are used to fill any gaps caused by the change in length of the play-out buffer.

11. The method recited in claim 7 wherein said gateway detects said answer tone and therefore initiates a switch from audio mode to VBD mode.

2. A system for operating a gateway comprising:

setting the length of the play-out buffer in a gateway when the gateway switches from audio mode to voice band data (VBD) mode by;

means for detecting the previous length of the play-out buffer in the previous audio mode,

means for adding a dilation factor to said previous length to obtain a new length, and means for setting said play-out buffer to said new length.

4. The system recited in claim 2 wherein the length of said play-out buffer in audio mode is set adaptively.

6. The system recited in claim 2 wherein audio concealment techniques are used to fill any gaps caused by the change in length of the play-out buffer.

8. The system recited in claim 2 wherein said switch from audio mode to VBD mode occurs when a first client places a call to a second client and said second client generates an answer tone.

10. The system recited in claim 4 wherein audio concealment techniques are used to fill any gaps caused by the change in length of the play-out buffer.

12. The system recited in claim 8 wherein said gateway detects said answer tone and therefore initiates a switch from audio mode to VBD mode.

13. A method of operating a gateway when a first client places a call to a second client in audio mode, causing said second client to generate an answer tone, said method including:

said gateway detecting said answer tone causing said gateway to switch to Voice Band Data (VBD) mode,

detecting the previous length of the play-out buffer in the previous audio mode,

adding a dilation factor to said previous length to obtain a new length, and

switching said gateway from audio mode to VBD mode with said play-out buffer set to said new length.

15. The method recited in claim 13 wherein the length of said play-out buffer in audio mode is set adaptively.

17. The method recited in claim 13 wherein audio concealment techniques are used to fill any gaps caused by the change in length of the play-out buffer.

19. The method recited in claim 15 wherein audio concealment techniques are used to fill any gaps caused by the change in length of the play-out buffer.

14. A system operable a gateway when a first client places a call to a second client in audio mode, causing said second client to generate an answer tone, and said gateway detecting said answer tone, the combination of:

means causing said gateway to switch to Voice Band Data (VBD) mode,

means for detecting the previous length of the play-out buffer in the previous audio mode,

means for adding a dilation factor to said previous length to obtain a new length, and

means for switching said gateway from audio mode to VBD mode with said play-out buffer set to said new length.

16. The system recited in claim 14 wherein the length of said play-out buffer in audio mode is set adaptively.

18. The system recited in claim 14 wherein audio concealment techniques are used to fill any gaps caused by the change in length of the play-out buffer.

20. The system recited in claim 16 wherein audio concealment techniques are used to fill any gaps caused by the change in length of the play-out buffer.

21. A computer readable medium having stored thereon computer instructions for causing a gateway to:

set the length of the play-out buffer in a gateway when the gateway switches from audio mode to voice band data (VBD) mode by;

detecting the previous length of the play-out buffer in the previous audio mode,

adding a dilation factor to said previous length to obtain a new length, and

setting said playout buffer to said new length.

22. The computer readable medium recited in claim 21 wherein the length of said play-out buffer in audio mode is set adaptively.

23. The computer readable medium recited in claim 21 wherein audio concealment techniques are used to fill any gaps caused by the change in length of the play-out buffer.