User's Manual

Grandstream Networks, Inc. GXV3140H USER MANUAL Page 46 of 146
FIRMWARE VERSION 1.0.7.2 Updated : 11/2010
G.711(a/μ)(PCMU/PCMA),GSM,G726-32,G.723.1,G.729A/B, G.722 and
L16-256.
When this has been configured, the system will select the preferred
vocoder from the list and the same order is sent with the SDP messages.
The user can change the preferred vocoder priority order by toggling with
the up and down buttons. It is recommended to use the default setting
“PCMU”; if other vocoders are chosen, there could be an audio
transmission error.
Preferred Video Codec Selects the preferred video codec from the available list. It is recommended
to use H.264.
H.264Payload type Selects the dynamic H.264 codec payload type (ranges from 96-127). The
default setting is 99.
H.263+ Payload type Selects the H.263+ codec payload type (ranges from 96-127). The default
setting is 103.
L16-256 Payload type Selects the L16-256 codec payload type (ranges from 96-127). The default
setting is 103.
H.263 Encoder Resolution Selects the resolution (CIF/QCIF) used for H.263 codec. The default
resolution is CIF.
Silence Suppression This controls the G723/G729 silence suppression/VAD. If set to YES, when
no audio is detected, the phone will send a small number of VAD packets
(instead of audio packets). If Set to NO, this feature is disabled. The default
setting is NO.
Voice Frame per TX This configures the number of voice frames transmitted per packet. (It is
recommended to set this based on the Ethernet IS packet limitation – 1500
Byte or 120kb/s).
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 example: if the codec is configured to be G.723 and “Voice Frames per
TX” is set to 2. Then in the INVITE request, the “ptime” value for SDP will
be 60 ms. This is because the G723 voice frame is 30 ms. Similarly, if the
setting is 2 and the codec is G729 or G711 or G726, the “ptime” value for
SDP in the INVITE request will be 20 ms.
If the voice frames per TX configuration exceeds the maximum value
allowed, the phone will choose the preferred codec and use the maximum
value allowed.