vad (dial peer)
To enable voice activity detection (VAD) for calls using a specific dial peer, use the vad command in dial-peer configuration mode. To disable VAD, use the no form of this command.
vad [aggressive]
no vad [aggressive]
Syntax Description
aggressive |
Reduces noise threshold from -78 to -62 dBm. Available only when session protocol multicast is configured. |
Command Default
VAD is enabled
Aggressive VAD is enabled in multicast dial peers
Command Modes
Dial-peer configuration
Command History
Release |
Modification |
---|---|
11.3(1)T |
This command was introduced on the Cisco 3600 series. |
12.0(4)T |
This command was implemented as a dial-peer command on Cisco MC3810 (in prior releases, the vad command was available only as a voice-port command). |
12.2(11)T |
The aggressive keyword was added. |
Cisco IOS XE Bengaluru 17.6.1a |
Introduced support for YANG models. |
Usage Guidelines
Use this command to enable voice activity detection. With VAD, voice data packets fall into three categories: speech, silence, and unknown. Speech and unknown packets are sent over the network; silence packets are discarded. The sound quality is slightly degraded with VAD, but the connection monopolizes much less bandwidth. If you use the no form of this command, VAD is disabled and voice data is continuously sent to the IP backbone. When configuring voice gateways to handle fax calls, VAD should be disabled at both ends of the IP network because it can interfere with the successful reception of fax traffic.
When the aggressive keyword is used, the VAD noise threshold is reduced from -78 to -62 dBm. Noise that falls below the -62 dBm threshold is considered to be silence and is not sent over the network. Additionally, unknown packets are considered to be silence and are discarded.
Examples
The following example enables VAD for a Voice over IP (VoIP) dial peer, starting from global configuration mode:
dial-peer voice 200 voip
vad