Polycom SIP 2.2.0 manual Dtmf Event RTP Payload, Acoustic Echo Cancellation

Administrator’s Guide SoundPoint IP / SoundStation IP

DTMF tones using the active voice codec or using RFC 2833 compatible encoding. The coding format decision is based on the capabilities of the remote end point.

Configuration changes can performed centrally at the boot server:

Central	Configuration file:	Set the DTMF tone levels, autodialing on and off times, and other
(boot server)	sip.cfg	parameters.
		• For more information, refer to Dual Tone Multi-Frequency
		<DTMF/> on page A-25.

DTMF Event RTP Payload

The phone is compatible with RFC 2833 - RTP Payload for DTMF Digits, Telephony Tones, and Telephony Signals. RFC 2833 describes a standard RTP-compatible technique for conveying DTMF dialing and other telephony events over an RTP media stream. The phone generates RFC 2833 (DTMF only) events but does not regenerate, nor otherwise use, DTMF events received from the remote end of the call.

Configuration changes can performed centrally at the boot server:

Central	Configuration file:	Enable or disable RFC 2833 support in SDP offers and specify the
(boot server)	sip.cfg	payload value to use in SDP offers.
		• For more information, refer to Dual Tone Multi-Frequency
		<DTMF/> on page A-25.

Acoustic Echo Cancellation

The phone employs advanced acoustic echo cancellation (AEC) for hands-free operation. Both linear and non-linear techniques are employed to aggressively reduce echo yet provide for natural full-duplex communication patterns.

When using the handset on any SoundPoint IP phones, AEC is not normally required. In certain situations, where echo is experienced by the far-end party, when the user is on the handset, AEC may be enabled to reduce/avoid this echo. To achieve this, make the following changes in the sip.cfg configuration file (default settings for these parameters are disabled):

voice.aec.hs.enable = 1 voice.aes.hs.enable = 1 voice.ns.hs.enable = 1 voice.ns.hs.signalAttn = -6 voice.ns.hs.silenceAttn = -9

For more information, refer to Acoustic Echo Cancellation <aec/> on page

A-34,Acoustic Echo Suppression <aes/> on page A-41, and Background

Noise Suppression <ns/> on page A-42.

4 - 44