H.323 Voice Codec Settings

Fax Voip T.38 Console supports different Audio Codecs for H.323. This is especially important in terms of some features. It is advisable to ask your H.323 provider about supported audio codecs. At least one audio codec must be selected. You should understand that G711 fax mode can only operate when using codecs G.711-ulaw or G.711-Alaw. On the other hand, T38 fax mode allows to use any audio codec that is available in your H.323 network. See also in the Voice Codecs requirements chapter of this user manual.

In the left panel you can see codecs available for use. The right panel shows codecs, selected by user. Codecs specified in the right panel can be overridden in the Outgoing Call Routing and Incoming Call Routing. Selected codecs can be arranged in preference order. By default the codec preference order only applies to outgoing calls. During incoming calls Fax Voip T.38 Console uses the preference order given by the remote side.

You can choose from the following Audio Codecs:

G.711-uLaw-64k (default)

G.711-ALaw-64k (default)

G.729* (for compatibility with T.38 only)

G.723.1

G.726-32k

GSM-06.10

iLBC

SpeexNB

SpeexWB

The following commands are available:

<Add> (or double-click selected entry in the Available codecs panel)

Use this button to add codecs for use with Fax Voip T.38 Console. You must select one of the codecs in the Available codecs panel before using this button.

<Remove> (or double-click selected entry in the Selected codecs panel)

Use this button to remove codecs from the Selected codecs panel. You must select one of the codecs in the Selected codecs panel before using this button.

<Up> and <Down>

Use these buttons to change preference order for the selected audio codecs. You must select one of the codecs in the Selected codecs panel before using these buttons.

Note that you can also do any of the above actions by selecting the appropriate command from the context menu of the list.

Notes

• Dummy G.729* codec enables to report G.729 Audio Codec support for Fax T.38 Gateways that do not support G.711 and other supported audio formats; use this codec only for resolving compatibility issue.
• Typically, if dummy G.729* codec is used, 'T38 Fax with Re-invite' mode for outgoing calls should be used too to ensure CNG tone generation. See in the 'T38, G711 and CAPI Fax Modes => Fax Modes (VoIP) => T38 Fax with Re-invite' section of this User Guide.
• The Voice Codec Settings specified in this pane are only applied to H.323 calls. To configure similar settings in the case of SIP, you should use the appropriate pane.