Default Media Profiles

The Oracle Communications Session Border Controller contains a set of default media profiles that define characteristics of well-known IANA codecs. You can not view the default media profiles' configurations, but you can override them by configuring identically-named media profile configuration elements.

Transcodable codecs are a subset of the default media profiles which the Oracle Communications Session Border Controller can transcode between.

Transcodable Codecs

The following list shows the transcodable codecs that the Oracle Communications Session Border Controller can add to SDP. These codecs all reflect default media profiles for their given names. Enter codecs in the configuration exactly as shown.

PCMU
PCMA
G729
G729A
iLBC
telephone-event
T.38
G711FB
G726
G726-16
G726-24
G726-32
G726-40
G722
G723
GSM
AMR
AMR-WB
EVRC0
EVRC
EVRC1
EVRCB0
EVRCB
EVRCB1

When creating an override media profile from a previously listed codec, the system ignores case sensitivity. Also, GSM = GSM-FR.

Preferred Default Payload Type

When the Oracle Communications Session Border Controller adds a codec with a dynamic payload type to SDP, it uses the lowest unused payload number. You can configure a preferred payload type for a dynamic codec by creating an override media profile. This makes the Oracle Communications Session Border Controller use your preferred payload type for insertion into SDP. If you configure a dynamic codec to use a preferred payload type, and that payload type is already in use, the codec will still be inserted into SDP, but with the first available dynamic payload type.

For example, you create a media profile for telephone-event with a payload type of 101. If telephone-event is added to SDP, and payload type 101 is already in use in the SDP, the Oracle Communications Session Border Controller will use the first available payload type in the 96-127 range when adding telephone-event.

Redefining Codec Packetization Time

You can configure a media profile with a packetization time (ptime) that overrides the codec's default ptime. Transcoding functions look up and use default ptimes when not specified in offered or answered SDP. Default ptime for most audio codecs is 20ms; some however are 30ms. See the Transcodable Codecs list for default values.

To change the default ptime for a codec, you must create a media profile that overwrites the default ptime parameter with your new packetization time. When SDP is received with no 'a= ptime' attribute or when adding the codec to egress SDP, the newly configured ptime is used.

New default ptime for a media profile is entered by typing "ptime=<x>" in the parameters parameter, where <x> is the new default packetization time.

mptime Support for Packet Cable

The SDP specification lacks the ability to specify unique packetization times per codec when more than one codec is listed in an m= line. The ptime attribute is not related to a specific codec but to the entire m= line. When multiple codecs appear on a single m= line, the PacketCable mptime attribute can specify different packetization times for each codec.

The Oracle Communications Session Border Controller adheres to PKT-SP-NCS1.5-I01-050128 and PKT-SP-EC-MGCP-I06-021127 for processing and generating mptime. The mptime line uses an integer to indicate the packetization time for each corresponding codec in the m= line. The dash character, "-", on an mptime line is used for non-packetized codecs, such as CN or telephone-event.

If the Oracle Communications Session Border Controller receives an invalid mptime, it is ignored and removed. If a valid mptime is received in the incoming SDP, its values will be used for packetization times of each corresponding codec and a valid mptime line will be sent in the outgoing SDP.

Valid:

    m=audio 10000 RTP/AVP 0 96 8
    a=mptime:20 - 30
    a=rtpmap:96 telephone-event/8000

Valid: 'ptime' attribute is ignored

    m=audio 10000 RTP/AVP 0 8
    a=mptime:20 30
    a=ptime:30

Invalid: dash cannot be first mptime value

    m=audio 10000 RTP/AVP 96 0
    a=mptime: - 20

When Oracle Communications Session Border Controller includes an mptime in an outgoing SDP, it will also always add a ptime attribute with the value of the most preferred codec. This is done to increase the interoperability with devices that do not support mptime.