Questions

• What is Opus DTX?
• What does it do?
• How does it affect call quality?
• What impact does Opus DTX have on audio bitrate?
• How will this affect the Session Inspector?
• When will Opus DTX be used and can it be disabled/enabled?
• How can I enabled Opus DTX?
• What SDK versions support Opus DTX?
• Can Opus DTX be configured?

Applies To

• Vonage Video API
• Opus DTX

Answers

What is Opus DTX?

Opus DTX (Discontinuous Transmission) is an extension of the Opus Audio codec used for audio in the Vonage Video API.

What does it do?

When Opus DTX is enabled it will encode silence at a lower bitrate by reducing the number of frames sent over the network.  This optimisation reduces the audio bandwidth used when participants are not speaking.

How does Opus DTX affect audio quality?

Opus DTX is applied to the codec when the audio input is silent.  When participants are speaking, audio quality will not be impacted.

How does Opus DTX impact audio bitrate?

Audio bitrate will only be affected when participants are silent.  During this time, bitrate will drop significantly lower that without DTX.  When participants are speaking, audio bitrate will be preserved at pre-configured levels.

How will Opus DTX affect the Session Inspector?

In the inspector, audio bitrates will be shown to fluctuate more significantly between speaking and silent portions of a stream.  Silent portions of a stream will have a visibly lower bitrate when viewed in the Session Inspector.

When will Opus DTX be used and can it be disabled/enabled?

At present, Opus DTX is disabled by default but can be enabled.

How can I enabled Opus DTX?

When initialising a publisher you can add the following publisher option:

• OpenTok.js — set the enableDtx property of the option parameter you pass into the OT.initPublisher()method.
• Android SDK — use the PublisherKit.Builder.enableOpusDtx() method.
• iOS SDK — set the OTPublisherKitSettings.enableOpusDtx property.
• Windows SDK — set the Publisher.Builder.OpusDtx property.
• Linux SDK — use the otc_publisher_settings_set_opus_dtx() function.

What SDK versions support Opus DTX?

Opus DTX is supported in version 2.22 of each of the Vonage Video Client SDK. (Beta support was added in version 2.21.1.)

Can Opus DTX be configured?

Beyond enabling and disabling DTX (as above) there are no further configuration options.