Articles and whitepapers

IP-based Multiroom AV (1/4/2006)

By Johannes Rietschel, Barix

Nowadays, systems for multiroom IP-based audio and video are not only being used in commercial buildings, but in private residences too. They are fast becoming as commonplace as lighting or integrated data networks. For the consumer, this means more choice, higher quality audio, higher performance, and easier handling, at lower cost.

The rapid proliferation of the Internet is making audio over IP the next big remote broadcast revolution, and offers the opportunity to deliver near real-time, high-quality audio and 'personal choice' radio. Within a house or estate, connections can be simplified using standard Cat5 (Ethernet) cable and standard network switches, or even wireless (WiFi) installations.

Traditionally, multiroom audio has been based on one central source of music that is able to play only one radio station or CD at the same time. This style of audio distribution around the home does not truly allow the delivery of personalised music simultaneously in every room or area. Modern technology however, can offer choice by streaming audio content onto a LAN or WAN network, and because a single-channel CD player or tuner is no longer needed, every room can get a different programme from a multichannel source such as a hard disk or the Internet.

Audio and video requirements

Today's technology can transform audio from analogue or digital sound sources into signals that are delivered to the wired or wireless network and sent to their destinations - be these sources next door or half way around the world. This technology can therefore be used to deliver personalised music to every room at any given time.

While video distribution over IP is doable and is in widespread use in the commercial security monitoring market, in residential applications affordable solutions that meet the demands of HDTV, which are practically all non-wireless, are only just emerging.

Excellent video quality needs a bandwidth of several megabits per second, compared with compressed audio which only requires 200-300 kilobits per second. While you can easily transport several simultaneous audio streams over a typical home network, it gets tricky with video, especially if wireless technology is used. For the moment therefore, we will concentrate on audio distribution rather than video.

IP-based multiroom audio distribution

Most equipment available to the consumer, installer and professional market is based on IP (Internet Protocol). Although proprietary use of Ethernet structured wiring, such as EtherSound and CobraNet, also exists, products using these technologies are mainly found in commercial studio, recording and theatre environments where many simultaneous channels of audio must be transported with absolute synchronicity at very high speed and low delay. These proprietary protocols are not routable over IP, and products based on them are relatively expensive.

As an example of an IP-based solution, we will look at the Barix multiroom audio distribution system. This aims to deliver crisp, high-quality audio over a standard network infrastructure using well-known standards such as MP3, IP, and RTP, and products that can be used with standard home network technology.

The Barix multiroom audio distribution system

The content is 100 percent digital and distributed and managed across a building's Cat5 LAN/WAN network or standard wireless IP equipment. Thus, networked audio products can coexist and be controlled by other networked devices such as PCs/laptops, palmtops, PDAs, IR remote controls, or home automation systems. The source of the music can be files on a server, as well as analogue or digital legacy sources such as a CD player, tape recorder, tuner, or radio.

These legacy audio signals are converted by the network-based IP 'Instreamer' audio encoder for digital audio streaming into high-quality MP3-streams. These streams are transmitted via the wired or wireless network and sent to their destination in real time, independently of the location. As the audio is streamed as fully-digital high-quality MP3 encoded data, no signal attenuation or noise problems will degrade the sound quality, irrespective of whether the speakers be feet, miles, or continents away.

The Barix Instreamer network based IP audio encoder for digital audio streaming into high-quality MP3-streams

The Barix Exstreamer network-based MP3-player for converting MP3-streams into music or voice

At the destination point, the intelligent network-based 'Exstreamer' MP3-player pulls the digital audio from the network and converts the MP3-streams into music or voice. Each room or area will require its own Exstreamer.

There will be one Instreamer required for each non-MP3 source channel, however if the source is a PC/central sound server that streams MP3 files, then no Instreamer is required at all. Users are able to control the central sound server from any room or area throughout the network by using the Exstreamer. Its built-in audio synchronisation technology also allows more than one unit to be installed in big rooms or halls, and a synchronisation function allows the user to play the same music in every room if they so wish, without that irritating time delays between signals that are characteristic of some digital systems.

Management of the multiroom audio distribution system is also possible using a PC. This allows the user to set up the different zones, access Internet radio stations, manage a huge audio collection, and generate playlists.

Advantages

Such a network-enabled audio installation offers a number of advantages. Since it only involves two types of device, namely the Instreamer and the Exstreamer, it is easy to set up. It is also an affordable investment, costing approximately GBP120-300 per device, depending on the version.

The system uses existing IP Internet or Intranet infrastructures to transmit high-quality audio to disparate locations, whether throughout a building or even across a continent. The devices are not PC-based, are very reliable, long-lasting and have very low power consumption - with the exception of the Exstreamer GOLD which has a powerful built-in amplifier to directly drive in-wall/in-ceiling speakers.

Indeed a new version of this device, the Exstreamer 100, can even play from a USB stick, so in commercial applications, this can be used as a backup function if, for whatever reason, the stream should fail.

Rear view of the Barix Exstreamer 100.

Summary

Using the Barix Instreamer/Exstreamer solution, the bandwidth required for the highest quality audio setting is only around 200kb/s, and for typical FM radio quality, is only around 64kb/s. Intelligent 'loss recovery' algorithms and robustness against network jitter, mean that the products can be used over existing network connections without the need to upgrade the connection. The solution easily routes audio to anywhere the network reaches, which means that with the rapid proliferation of IP connectivity, audio can be provided almost everywhere - seamlessly, reliably, and affordably!

Johannes Rietschel is the CEO of Barix AG, specialist in R&D of state-of-the-art IP-based communication and control technology.

www.barix.com