Audio over IP – the bright future of multi-channel high resolution audio
You might have heard of ‘Audio-over-IP’ (AoIP) – a term that is becoming increasingly important in today’s audio industry. The abbreviation ‘IP’ in ‘Audio over IP’ is short for ‘Internet Protocol,’ meaning the protocol used to send data across packet-switched networks. Computer networks and telecommunication devices (like IP audio codecs and mobile phones) make use of packet-switching by routing data packets individually between two devices through Local Area Networks (LAN) or Wide Area Networks (WAN). The also widely known term ‘Voice over IP’ (VoIP) refers to the technology used to send compressed voice service data packets that telecommunication or Internet services (such as Skype) rely on.
The requirements for IP based telephone systems led to the development of many of the ‘Audio over IP’ options that exist today. While the goal of ‘Voice over IP’ consists in reaching a high signal compression and undisturbed data flow across network boundaries, the requirements for professional audio and broadcast applications are significantly different: full signal transparency, very low latency, a high channel count, and a stable network performance are absolutely crucial. Since the progress made in network technologies like Gigabit networking have by now become widely accepted, the mentioned requirements can today finally be fully realized. This development essentially turns ‘Audio over IP’ into the future of audio distribution as it allows for an unprecedented level of flexibility and efficiency.
A short History of Digital Audio Signal Routing
Since the early 1980s, complex audio signal routing has most often been realized with the help of Time Division Multiplexing (TDM), a method of transmitting and receiving independent digital signals through a single cable that can, however, carry more than one channel. With help of this technique, the audio signal is divided into many segments of short duration, which are later reassembled at the receiving end. The broadcast industry first adopted stereo digital audio (AES3) and later multi-channel digital audio (MADI) in order to transport signals. A growing number of audio channels called for digital audio routers that could handle a larger capacity of digital signals. However, TDM connections are not very efficient since interconnections often also carry useless information. Many of today’s broadcast infrastructures nevertheless still use large-scale TDM routing solutions and both AES and MADI digital audio in order to interconnect various devices.
Much of recently conducted research was driven by the desire to overcome the inherent inefficiency of TDM connections. By turning signals into packets and sending multiple packets through the same cable, the capacity of that cable quickly rose to thousands of channels. The first ‘AoIP’ solutions offered by systems like CobraNet, EtherSound, or Q-LAN made use of already existing IT networks in order to deliver a limited number of channels through a standard 10 or 100Mbit network. Other solutions used standards that were limited to lower OSI layers in order to increase efficiency, yet they required specific network hardware and in addition remained incompatible with other Ethernet or IP network traffic. Nowadays, network technologies finally allow us to fully realize real-time applications: networking standards have evolved to an extent that turns interactive audio applications into a realistic possibility.
While established ‘AoIP’ standards like Dante, Ravenna Network, and AVB have been designed with the fields of broadcasting and live performance events in mind, they have also paved the way for multi-channel setups and the distribution of real-time high resolution audio streams in recording and mix-down studios. It is, for instance, now possible to work with multiple loudspeaker setups like 5.1, Dolby Atmos, or Auro 3D simply by using a single Ethernet router to distribute audio material among several devices or, as in our case, several studio monitors.
As is well known, network-based systems rely on conventional and inexpensive off-the-shelf IT technology originally designed to forward a large number of data packets without having to deliver them in real-time. It is precisely for this reason that IP technology has been at a disadvantage with regard to audio transport. Yet the technological progress that has been made in this field (Gigabit switches etc.) makes it increasingly attractive for broadcasters, concert halls, and studio professionals to implement AoIP technology. Besides the tremendous cost-saving effect on equipment, network-based solutions for audio delivery hold the potential of enabling broadcasters, recording studios, and live venues to leverage their existing infrastructure and to achieve greater flexibility in terms of set-up, network configuration, and content sharing.
HEDD’s modular input card system, which we call the HEDD Bridge, brings versatile digital input connectivity including two AoIP options to the world of professional monitoring. For the first time, it now becomes possible for studio monitors to be integrated into today’s most established audio network protocols: Audinate’s Dante and Ravenna Network / AES67.
Loudspeakers in AoIP networks
Here are a few examples of how loudspeakers can be used in an AoIP environment:
- You can directly connect your computer to loudspeakers via a CAT.6 Ethernet cable in order to stream high resolution audio
- In complex multi-channel setups (Dolby Atmos, Auro 3D, etc.), multiple separate loudspeakers can be fed with a single high-resolution audio stream and each one of these speaker channels can be controlled individually by software control applications
- Audio devices in different rooms or facilities (e.g. movie theaters, conference rooms, live concerts and music festivals) can be controlled from one or multiple workspaces connected to the Ethernet network
- AoIP will enable broadcast engineers to simplify the in-house signal distribution in broadcast stations
With many years of expertise in the field of professional studio monitors, our team at HEDD | Heinz Electrodynamic Designs feels that it is time to move on and take the next step by combining sophisticated analog loudspeaker designs with the latest developments in digital audio distribution technologies.