Signal distribution in the studio has long involved massive amounts of wiring and large patch panels. Analog signal distribution required separate physical channels for every signal. Switching and routing required expensive crosspoint analog switching devices. There was required a constant effort to maintain signal integrity and three wire balanced signals were often employed. The move to digital has made signal integrity much easier to achieve and has even allowed the multiplexing of multiple channels onto a single physical channel. This is often done using proprietary techniques and different manufacturers use different techniques and technologies. Switching and routing still involve expensive proprietary technologies and equipment.

There has been a long time interest in a networked technology for signal distribution similar to the technology used to share data and communicate between computers in an office or over the internet. This would allow flexible topologies, easy connectivity, and even wide area connectivity. In fact several standards have been put forth often using patented proprietary techniques and technologies. At this years IBC 2010 convention in the Netherlands a small consortium of companies put forth a proposed IP based standard for digital signal distribution Called RAVENNA.

Why IP Based?

The easiest answer is, to leverage the enormous investment in IP based networking that is used in the IT industry at this time. Other advantages are not to be overlooked. IP based networking protocols are independent from the underlying physical networking structure. They are scalable with the performance of the underlying network technology. The faster the physical network the more channels available for distribution. It is also completely compatible with existing data communication protocols base on IP and would allow data and signal distribution to coexist in the same network. This allows for the simplified participation of computer workstations in the signal distribution process and even allows wide area distribution of signals via existing WAN's and the public internet. While networked based solutions rely on IT industry developed equipment based on the ultrafast distribution of large numbers of packets of data with no regard for real-time constraints, the numerous advantages of using this mature and ubiquitous technology are too numerous to overlook.

Is This Not Just VOIP?

Perhaps it can be thought of as voice over IP on steroids. The goals of VOIP are significantly different than those of audio signal distribution over IP. The main goal of VOIP is to deliver an uninterrupted stream of intelligible voice content over an IP network. This is a very bandwidth limited single with no real-time synchronization required. The signal can be delayed by considerable elapsed time as long as it is delivered continuous and uninterrupted at it's destination. The delivery of multiple, synchronous, full audio bandwidth signals poses a far greater challenge than anything previously tried over an IP network.

An Overview of The Technology

Being and IP based solution RAVENNA is based on protocols on or above the OSI layer 3. This means it can be used over a wide range of physical networking technologies with all of the Ethernet implementations fully supported and can even be implemented over the internet. Since IP is it's native protocol it is only natural that RTP real time protocol would used for media streaming. Basic payload formats are 16 and 24 bits at 48kHz sample rates. Unicast and Multicast streaming is supported. A device attached to the network receives a unique IP address and then announces it's presence, capabilities, and services provided so that other RAVENNA capable devices on the network can interact. Being IP based it allows further vendor specific protocols to be implemented alongside the RAVENNA standard protocols. In the pro-audio environment synchronization is essential. In RAVENNA PTPv2 or Precision Time Protocol allows synchronization of real-time clocks in the low nanosecond range. Sample accurate synchronization can be achieved even without PTP implementation. Synchronization can even be achieved across a WAN using the GPS precision time element to synchronize local master clocks. Finally implementation of QoS assures RAVENNA expedited access to the IP network as it competes with other data services on the shared network.

The Importance of Open Standards

The fact that RAVENNA is an open standard is important. An open standard is one that is free of technology that is patented or constrained by proprietary process or technology. This means that it is available freely to developers of any ilk. You can develop a product or software in your garage incorporating this standard without the worry of licensing fees or possible lawsuits down the road. Competing products can not be blocked from incorporating the technology. If the standard is widely adopted end users can seamlessly mix and match equipment from major manufacturers, small niche market developers, or a custom developer to match their specific needs.

The Bottom Line

IP based standards like RAVENNA will allow distributed audio signal networks to be as cheap and easy to assemble as todays computer networks. Integration of computer workstations, data storage systems, and a wide range of equipment will become plug and play. RAVENNA is currently being developed largely by players in the broadcast industry, but the sound system installation and live sound industries have shown great interest. It has the possibility to be a game changer but it depends entirely on how wide spread support for the standard becomes. I for one look forward to it's adoption and hope that it will one day become ubiquitous. For further information see ravenna.alcnetworx.com