AMR-WB

The AMR-WB codec (G.722.2) is a 16 Khz sampled wideband codec. AMR-WB like AMR-NB needs to be licensed on the node it is being configured on and is licensed on a per channel basis. Refer to the Licensing (Gateway Mode) topic for more information on that. When initially configuring the node object, the Media Mode field needs to be configured. The AMR-WB codec is supported in the Media Modes HD Audio and Audio Dynamic Density Management. Refer to the information below.

Note: Using the AMR-WB resource in connection with a Dialogic® product described herein does not grant the right to practice the AMR-WB standard. To seek a patent license agreement to practice the standard, contact VoiceAge Corporation at http://www.voiceage.com/licensing.php .

Overview of AMR-WB codec on IMG 2020

The following information describes what is supported as well as its limitations when configured on the IMG 2020.

General Information

• Refer to the topic for information on payload sizes and payload types.

• AMR-WB supports Audio calls only. Multimedia is not supported.

• AMR-WB does not support Silence Suppression.

• AMR-WB supports the following compression rates: (6.6, 8.85, 12.65, 14.25, 15.85, 18.25, 19.85, 23.05, and 23.85 kbps).

• Extended AMR-WB is not supported.

• Media Modes HD Audio and Dynamic Channel Density Management are the two Media Modes that support the AMR-WB codec.

• AMR-WB is not supported in an RTP Redundancy scenario.

• AMR-WB can be transcoded to any codec supported on the IMG 2020.

• When passing a call from AMR-WB on the incoming side to AMR-WB on the outgoing side, the signal quality will be lost because of the decoding from an RTP stream to PCM data and back again. Passing HD Audio through the IMG 2020 can be achieved, however the signal on the outgoing side will be degraded so it is no longer a High Definition quality signal.

• AMR-WB is not supported when SRTP is enabled.

• As with AMR-NB, the IMG 2020 supports both the Octet-Aligned mode and the Bandwidth-Efficient mode. 

SDP Information

• The AMR-WB codec like any other codec will negotiate the SDP.

• The text string in the SDP will be displayed in the SDP as: amr-wb/16000.

• Octet-Aligned versus Bandwidth-Efficient mode is displayed in the SDP as: octet-align=1 or octet-align=0. As per RFC 4867, if not present, Bandwidth-Efficient is employed.

• The SDP does NOT support the mode-set or mode-change-capability strings. The media layer manages the rate and mode changes. 

SRTP Mode -vs- AMR-WB

The Web GUI WILL ALLOW configuring of SRTP when utilizing the AMR-WB codec. Since SRTP and AMR-WB are not supported when configured together, any error cases are handled at the SIP level. Below is table listing the behavior of the IMG 2020 when the IP Profile is configured into a SIP channel group that is communicating with an External Gateway that is configured for SRTP.

 Incoming

Outgoing