AN2775, Tone Event Detection in Packet Telephony Using the StarCore SC140 Core

1 Tone Event Detection Basics ......................................2 1.1 Tone Event Detector Architecture ..............................2 1.2 Phase Detection With Frequency Offset Compensation .............................................................4 1.3 Summary of Theoretical Results .................................6 2 Tone Event Detector on StarCore ...............................8 2.1 Automatic Level Control (ALC) .................................8 2.2 Tone Indication ...........................................................9 2.3 Tone Indicator Counter ...............................................9 2.4 Finding the Closest Reference Frequency Tone .......10 2.5 FIR Filtering Implementation ...................................10 3 Tone Events in Packet Telephony ............................11 4 RFC2833 Overview ..................................................11 4.1 Payload Format for Named Telephone Events .........12 4.2 Sending and Receiving Named Telephone Event Packets ......................................................................15 4.3 Payload Format for Telephony Tones ......................16 4.4 Multiple Tones and Named Events in One Packet ...17 5 Conclusion ................................................................20 6 References ................................................................21 Tone Event Detection in Packet Telephony Using the StarCoreTM SC140 Core