AEQ
PHOENIX ALIO
38
See more details in section 4.3 of this manual.
•
The rest of options to be configured are:
o
FEC mode: this option allows you to configure whether FEC (Forward Error
Correction) is used or not (there is a trade-off for a bigger binary rate). See
section 4.4.
o
Local media port: this option allows you to configure the value of the IP
port selected to transmit audio at origin over IP. Minimum value 1,024.
Maximum value 65,534. Default values: 5004 (PROG) and 5008 (COORD).
o
Adaptive/Fixed and Adaptive buffer max/Fixed buffer length: this option
allows you to configure the type and maximum size of reception buffer. See
section 4.4.
o
Symmetric RTP: this option allows you to force the local unit to send audio
to the same IP and port from which it is receiving audio. The destination
port specified when making the call will be ignored when we receive
packets from the remote equipment. This option will allow you to connect to
an audiocodec with unknown IP and/or port (because it’s behind a router
with NAT, for instance).
Each unit will send audio to the "Local media port" of the remote equipment automatically,
thanks to the SIP signaling protocol. That signaling also accomplishes coding profile negotiation
and call establishment / release from any of both sides of the communication once the remote
equipment has been identified by its IP address and reached.
4.2.4. Sending audio to multiple destinations: Broadcast, Multicast and Multi-unicast.
It is possible to send the same audio RTP stream to several different destinations in "RTP raw"
mode (see section 4.2.1). There are several possibilities to do so (see "AEQ ControlPHOENIX"
manual):
a) Broadcast: the audio stream can be sent to all the equipments within a local network, only
by specifying a special address in the destination address field. This address is calculated as
the network address with the equipment part filled with 1’s. For instance: if the IP address of our
codec is 192.168.20.3 and network mask is 255.255.255.0, the corresponding broadcast
address is 192.168.20.255. However, if the network mask was, for example, 255.255.0.0, then
the broadcast address would be 192.168.255.255. The audio will be sent to a given port, so the
receiving equipments should have "local media port" set up to this same port so they are able to
receive the RTP stream.
This mode is not recommended for big networks and is usually blocked by the switches and
routers, so its use is restricted to small, well managed local area networks.
b) Multicast: it is also possible to send the audio stream to a special "multicast" address, for
example, 239.255.20.8. If the receiving equipments call to that same IP, they will receive the
audio that is being sent provided that their "local media port" matches the one the transmitter is
sending the packets to. Phoenix ALIO implements IGMP (Internet Group Management Protocol)
in order to subscribe to multicast group. Similarly to broadcast, multicast traffic is usually
blocked by switches and routers, so its use is restricted to local area networks too.
c) Multiple-unicast: Phoenix units can send the same RTP stream to several different IPs by
replication of the encoded audio. This can traverse switches and routers in the same way it
would do if it was a simple (unicast) RTP Raw stream, although it is limited to a certain number
of destination IPs depending on the type of coding algorithm
That parallel streams or "replicas" at nothing more than IP address + port pairs, where audio
copies are to be sent normally. When a contact is created or edited, it is also possible to specify
whether particular replicas use FEC (forward error correction) if it is enabled for that channel, or
disable it for certain streams (because they use stronger links, for example). If the above list is
empty, the audio stream will be sent to the IP + port specified when making the call (main
address in the contact).