ScoopTeam - User manual - Draft 0002
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2.3. Audio transmission
The ScoopTeam features in all versions an Ethernet interface for IP protocol networks. Additional
interfaces are available as options: ISDN interface (BRI), mobile network access, Wi-Fi interface (
NYA
).
2.3.1. Ethernet/IP interface
The IP interface is a 10BaseT/100BaseT Ethernet interface allowing transmission of the audio programs
in a wide range of possible bit rates. Audio streams are always transported under the RTP/UDP protocol.
AoIP transmission
The ScoopTeam performs AoIP (Audio over IP) transmission, exchanging unicast streams with one (or
two) remote device(s), generally bidirectional. This mode can be used on all types of networks links, LAN
or WAN, including links via Internet. The ScoopTeam implements the SIP protocol, which is required for
audio contribution links by the EBU Tech3326 recommendation, also known as “N/ACIP”. Links can be
set up in three ways:
“Peer to peer” SIP connection between two compatible units.
Use of a SIP proxy server to set up the link, or a SIP PBX.
“Peer to peer” connection without SIP, called “Direct RTP”. This operation mode can be used
for interoperation with devices that do not support SIP, or for overcoming possible network
blocking that would specifically affect the SIP protocol.
The audio coding algorithm can be selected depending on the required quality and the available
network bandwidth. The available algorithms are described in 2.2, Audio encoding and decoding.
SIP and SDP protocols
The SIP protocol is a signalling protocol used for live media transmission over IP connections, which
allows the interoperation with IP phones and SIP compatible audio codecs, in a way similar to ISDN or
telephone connections. Details about the SIP protocols can be found in TBD.
One significant advantage is the inclusion of SDP, a protocol which allows the connecting devices to
automatically negotiate and agree on the coding profile to use. Thanks to this system, it is not necessary
to set the units in the same way before setting up a connection. Moreover, the calling party needs not
know how the remote unit is configured before initiating a link.
Note: the SIP protocol does not mandatorily imply the use of a server. Codecs can set up point-to-
point links using this protocol, and benefit from some its advantages.
Conversely, for the “Direct RTP” mode, which includes no signalling, it is necessary to configure
beforehand in the same way the two units to be connected.
Double AoIP codec
With the SIP protocol, the ScoopTeam can operate as two mono AoIP codecs. Each of the codecs can
have its own SIP registration and is managed independently from the other codec.
The available algorithms for each codec are described in 2.2.2, Double codec mode (see Table 3 –
Double codec - Available coding depending on network).
Packet duplication
ScoopTeam also proposes an RTP transmission mode with enhanced reliability, using packet replication.
When enabling this mode, every packet is transmitted twice; with such system a lost packet has no
effect since the receiver still gets the other copy of the packet. In this way, stable links can be obtained
even with a high packet loss rate. Of course, as a disadvantage the bit rate is double; you must make
sure this stays compatible with the transmission medium.