allow-codecs

allow-codecs—The allow-codecs parameter configures the codecs that are allowed and/or removed from the SDP. A blank list allows nothing, * allows all codecs, none removes all codecs, the :no designation blocks the specific codec or class of media, and the :force designation is used to remove all non-forced codecs.

The allow-codecs parameter is configured in the following way:

• <codec>:no—blocks the specific codec
• *—allow all codecs.
• <codec>:force—If any forced codec is present in an SDP offer, all non-forced codecs are stripped from the m- line.
• audio:no—audio m= line is disabled
• video:no—video m= line is disabled

For example, if you configure PCMU in the allow-codecs parameter, the PCMU codec, received in an SDP message is allowed on to the next step of transcoding processing, and all other codecs are removed.

The order of precedence is for removing codecs according to codec policy is:

1. <codec>:no—Overrides all other allow-codecs parameter actions.
2. audio:no / video:no. An allow-codecs line like “allow-codecs PCMU audio:no” disables the PCMU m= line because audio:no has a higher precedence than the specific codec.
3. <codec>:force
4. <codec> Specific codec name and those codecs configured in the add-codecs-on-egress list.
5. * has the lowest precedence of all flags. For example "allow-codecs * PCMU:no" allows all codecs except PCMU.