Network for professional audio and video

Features

• high performance at low cost

• guaranteed sub-msec latency

• uses standard cat-5 building wiring

• truly plug-and-play

  • any network port can be connected to any other using only straight-through cables

  • control software can easily discover what units are on the network and what their capabilities are

  • media can be routed from any source to any destination

  • network protocols discover the best route for each connection

• wide choice of configurations, including

  • resilient dual ring (no additional equipment required)

  • star-connection into a switch

  • follow-on connector allows switch connection to be shared

• service classes appropriate to audio, video, and data

  • "best effort" traffic cannot impede other service classes

• audio conforms to AES47-2006 standard

• compatible with ATM, IP, and DWDM networks

Network technology

Brunhilde combines the best features of cell-based, synchronous, and packet networks.

The network service is currently cell-based. Cell size and connection management are compatible with ATM networks, allowing Brunhilde networks to be seamlessly connected to private ATM networks and public ATM services. Future implementations will use Flexilink technology.

The links that make up a Brunhilde network segment are more tightly synchronised than on standard ATM networks, to further reduce end-to-end latency and to minimise the phase difference between audio signals at different interfaces.

Ethernet (IEEE 802.3) standards are used for the physical connection between units. This reduces hardware costs while still providing connections of up to 100 metres over standard building wiring and longer distances over fibre. In many cases all that will be needed for installation is to make the necessary connections at the patch panel and plug the equipment into the wall. The ability to daisy-chain several pieces of equipment together means that only one wall socket is required at each location, not one per piece of equipment.

Brunhilde subnetworks in different locations may be connected together via a number of technologies, in addition to ATM networks. Brunhilde protocols may be used directly over dark fibre or a "lambda" of a DWDM network, or (for applications where lower real-time performance can be tolerated) tunnelled through IP on a LAN or even over the Internet.

Timing

The most critical timing parameter where units are daisy-chained together is the transit time through each one. This is less than 1 µsec, so the transit time from end to end of a chain of 30 units is less than 30 µsec.

The total time between audio input and audio output on a single segment depends mainly on the packetisation time, which is the time taken to fill a cell and thus is less for multi-channel audio and for higher sample rates; some examples are given in the table below.

Transit times where sender and receiver are not on the same segment will, of course, depend on how the segments are joined together. An ATM network within a metropolitan area should add no more than 200 µsec; other networking technologies will add considerably longer delays. Over wider areas, delays in the cable of around 1 msec per 200 km must be taken into account; these delays are unavoidable, being related to the speed of light through glass fibres.

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