28
G711 Alaw
G.711 is an ITU-T standard codec that uses audio companding.
Companding algorithms reduce the dynamic range of an audio
signal. In analogue systems, this can increase the signal-to-noise
ratio achieved during transmission and, in the digital domain, can
reduce the quantization error.
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the
μ
-law algorithm (used in North America and Japan) and
A-law algorithm (used in Europe and the rest of the world).
G711 Ulaw
See G711
μ
-law above.
G729
G.729 is an ITU-T standard codec that operates at 8 kbit/s. It is
mostly used in VoIP applications with low bandwidth requirement.
On phone:
(
MENU
) >
SETTINGS
>
ADVANCED
> (PIN) >
MEDIA
>
CODEC
(6,2,4,1).
SRTP
If set to disabled, the media is sent using RTP. Note that despite
this setting, the KX-HDV800 will still use a secure channel if the
opposite device demands it.
If set to optional or mandatory, a padlock will be shown in the bot-
tom right-hand corner of the screen. If the other devices support
SRTP, the padlock will be locked. Otherwise, an open padlock
will be displayed.
If set to mandatory, the call will not be connected if the other
devices do not support SRTP.
Secure signalling
The SIP messages (signalling) and the SRTP cipher key are sent
on a different channel than the media and are not affected by the
RTP/SRTP setting. To ensure a secure connection, the signalling
must be secured using
TLS
or
SIPS
, see page 22. Note that the
SIP transport setting must be set accordingly.
On phone:
(
MENU
) >
SETTINGS
>
ADVANCED
> (PIN) >
MEDIA
>
SECURITY
(6,2,4,4).
SETTINGS
Security
The media in VoIP calls is usually sent using the RTP protocol (Real-time Transport
Protocol). RTP is a standardized packet format for delivering audio and video over the
Internet.
65736HFXUH5HDOWLPH7UDQVSRUW3URWRFROLVDQH[WHQVLRQRI573WRSURYLGHHQFU\S
-
tion, message authentication and integrity for the audio and video streams.
All devices must support SRTP to establish a connection. It is therefore possible to set
SRTP as disabled, optional or mandatory.
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PDQGDWRU\
The SRTP function can not be used in Commonwealth of Independent States
