Grandstream Networks GHP6 Series Administration Manual page 24

Codec Negotiation
Priority
Use First Matching
Vocoder in 200OK SDP
ILBC Frame Size
G726-32 ITU Payload
G726-32 Dynamic PT
Opus Payload Type
DTMF
DTMF Payload Type
Enable Audio RED with
FEC
Audio FEC Payload Type
Audio RED Payload Type
Silence Suppression
Voice Frames Per TX
This configuration will be included with the same preference order in the SIP SDP message.
Configures the phone to use which codec sequence to negotiate as the callee. When set to "Caller", the
phone negotiates by SDP codec sequence from received SIP Invite; When set to "Callee", the phone
negotiates by audio codec sequence on the phone. The default setting is "Callee".
Configures the phone to use the first matching codec in the 200OK message.
The default value is 0.
Sets the ILBC (Internet Low Bitrate Codec) frame size if ILBC is used. Users can select it from 20ms or
30ms.
The default setting is 30ms.
Configures G726-32 payload type for ITU packing mode. Payload 2 is static and payload dynamic is
dynamic.
The default setting is "2".
Specifies the G726-32 payload type, and the valid range is 96 to 126. The default setting is "126".
Defines the desired value (96-126) for the payload type of the Opus codec.
The default value is 123.
Specifies the mechanism to transmit DTMF (Dual Tone Multi-Frequency) signals.
There are 3 supported modes: in audio, RFC2833, or SIP INFO.
● In audio, which means DTMF is combined in the audio signal (not very reliable with low-bit-rate
codecs).
● RFC2833, which means to specify DTMF with RTP packet. Users could know the packet is DTMF in
the RTP header as well as the type of DTMF.
● SIP INFO, which uses SIP INFO to carry DTMF. The defect of this mode is that it's easily to cause
desynchronized of DTMF and media packet if the SIP and RTP messages are required to transmitted
respectively.
The default setting is "RFC2833".
Configures the RTP payload type that indicates the transmitted packet contains DTMF digits. Valid range is
from 96 to 126.
Default value is 101.
If set to "Yes", FEC will be enabled for audio call.
The default setting is "No".
Configures audio FEC payload type. The valid range is from 96 to 126.
The default value is 121.
Configures audio RED payload type. The valid range is from 96 to 126.
The default value is 124.
Enables the silence suppression/VAD feature. If it is set to "Yes", when silence is detected, a small quantity
of VAD packets (instead of audio packets) will be sent during the period of no talking.
If set to "No", this feature is disabled. The default setting is "No".
Configures the number of voice frames transmitted per packet. When configuring this, it should be noted
that the "ptime" value for the SDP will change with different configurations here. This value is related to the
codec used and the actual frames transmitted during the in payload call. For end users, it is recommended to
use the default setting, as incorrect settings may influence the audio quality.
The default setting is 2.
Preferred Video Codec