At the core, the Logitek JetNet and Axia Livewire AoIP systems are very similar. Both stream audio using RTP over UDP multicast packets, following Internet standards created for videoconferencing. Where they differ comes down to timing and mnemonics. When we set out to integrate the studios at KSBJ, we knew we could pick up the audio streams, but we had to find a way to stay synchronized, and we had to figure out how to name the streams coming from the Axia equipment.
On the timing front, things are starting to get easier. At the 2012 NAB Show, Axia announced support for Ravenna in its new products. Ravenna, a consortium backed by European manufacturer Lawo, calls for using the IEEE 1588 precision timing standard via PPTP, which is the same standard that Logitek already uses. Of course, when we were building KSBJ we didn''t have this in common, so we connected an AES output from an Axia node to a Logitek JetStream sync input and rate locked the JetStreams to that AES signal.
Every stream in an AoIP system has a unique multicast IP address. Logitek uses a common multicast “announce channel” for each JetStream to tell each other what streams it has, their addresses, and their names, allowing each JetStream to build a channel guide of all available sources. At the time we were developing the JetStream, no standard channel guide existed, so we created our own (which holds true for the other AoIP manufacturers as well). To support other systems such as Axia, we created a translation table to fill in the multicast address of the stream coming from the other devices and how it should be labeled in the Logitek system. Standing at a console, all of the sources look and sound the same, regardless of whose box they came into first.
Looking ahead to the future, new standards such as AVB and Ravenna have come about since KSBJ was installed that unify both timing and mnemonics. We are currently evaluating how these new methods might make the installation of a blended networked console system easier. While the translation table does the job for now, finding standards that all manufacturers can agree upon will make audio networking universal.
Davis is technical support manager at Logitek.