Audio Buses - Digigram IQOYA *SERV/LINK User Manual

Audio samples decoded by *SERV/LINK are played to the selected audio outputs. Audio outputs can be analog,
AES/EBU, MADI, or RAVENNA / AES67 . In case of an IQOYA *SERV/LINK that features both analog and digital
outputs (for instance *SERV/LINK 882), the decoded audio signal is available on both the analog and AES/EBU
outputs.
Note that decoded audio samples can also be sent to internal audio buses, and audio buses can also be sources
to be encoded. See paragraph 4.4 below.
4.2. Programs
On the encoding section of IQOYA *SERV/LINK, a program is the encoding of one or several audio inputs. A
program is then defined by the following parameters:
● the audio mode: mono, stereo, multi-channel.
● the audio input(s) that receive the signal to be encoded. The number of inputs is given by the audio mode.
They are consecutive inputs for stereo and multi-channel modes.
● the encoding format: algorithm, bitrate, sampling frequency.
On the decoding part of IQOYA *SERV/LINK, a program is the decoding of an audio source to the audio outputs.
A program can be composed of three decoding priorities, with automatic switching from a priority to another in
case the audio source is lost. Audio sources of the decoding priorities can be an RTP stream (raw RTP), an
HTTP stream (Icecast/Shoutcast), audio inputs, sound files or playlists stored locally.
4.3. IP services
IP services are the way programs are streamed over the IP network. An IP service can include one audio
program, or several multiplexed audio programs (case of MPEG-TS MPTS encapsulation).
When IQOYA streams, an IP service can be sent to one IP destination (unicast or multicast), or several IP
destinations (multi-unicast or multi-multicast). The main parameters that define an IP service are:
● the streaming protocol: RTP, UDP, HTTP
● the encapsulation: raw (no encapsulation), MPEG-TS
● the audio program(s) included in the service: one program in case of raw or MPEG-TS SPTS transport;
several programs in case of MPEG-TS MPTS transport
● the FEC scheme (IP data redundancy)
● the destination IP address and port. Several destination IP addresses and ports can be declared
(multi-unicast / multi-multicast).
When IQOYA decodes, it listens to IP services and unpacks the IP frames in order to extract and decode the
audio contents.

4.4. Audio buses

The audio buses serve for transcoding IP audio streams. An audio bus can be selected as the output of one or
several output programs. In case several output programs are connected to the same internal bus, the bus mixes
the audio from the different programs. Note that an output program can be simultaneously connected to an audio
output and an internal bus.
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