CHAPTER 1
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INTRODUCTION
1 Introduction
Overview
The Omnia MPX Node is a purpose-built broadcast codec for transporting FM composite
(MPX) signals over IP networks. Like its namesake (the classic Axia xNode), Omnia
MPX Node is a building block technology that helps stations leverage the growing power
and capability of data networking. By transporting an FM composite signal rather than
Left/Right audio, broadcasters can keep their on-air processing and RDS encoding at the
studio, then deliver a transmission-ready, peak controlled FM multiplex signal directly
to an FM transmitter without the need for transmitter-side peak limiting or stereo
generation. Since MPX is transported over IP, signals are routable, and one-to-many
distribution of “carbon copy” processing becomes possible. Each MPX Node can be set
to either encode or decode, and a pair of units creates an end-to-end system. Omnia SST
users can connect to the MPX Node, and stations with an Omnia 9 processor can purchase
an Encoder license, such that MPX over IP signals can be sent directly via IP from the
processor to a decoder.
About the μMPX Codec
MPX Node utilizes μMPX (“micro” MPX), a specially designed audio codec pur-
pose-built for FM radio that is able to transport high-quality Multiplexed FM signals over
a relatively small 320kbps data pipe using UDP. While some companies have full-band-
width “linear” MPX over IP offerings, distribution of such streams requires extremely
high dedicated bandwidth, typically 2 megabits (Mb) or more. μMPX slashes the amount
of bandwidth needed for distribution by nearly 84% to a remarkable 320kbps. By reducing
data requirements, high-quality multiplexed audio can be economically routed from
any audio processor, over IP, and directly into an exciter. Unlike codec offerings that are
designed explicitly for stereo audio (MP3, AAC, etc), μMPX is purpose built for com-
posite FM signals. μMPX uses a unique perceptual masking strategy, leveraging the native
properties of FM multiplexed signals. For STL use, this approach provides a double
benefit over stereo audio codecs because: