HyperMAC is a proprietary digital audio point-to-point connection technology operating over Gigabit Ethernet originally developed by Sony Pro-Audio Lab and now owned by Klark Teknik.
HyperMAC can be networked via dedicated routers, such as the Midas DL461 Audio System Signal Router, to provide channel-by-channel audio routing (like a patch bay), as well as packet switching for the auxiliary data messages. Routing is centralised, not distributed, giving better latency control, better reliability and finer routing granularity than distributed audio networks. It uses Ethernet frames transmitted over the physical layer only of the Ethernet technology – the cables and transceivers at each end. A deterministic protocol is used that is essentially a time-division multiplex (TDM) at the hardware level. This approach offers robust, low-latency and deterministic latency audio routing, with the benefits of a true packet-switched network for the control data.
The frame-based method allows for simultaneously high channel counts and very low deterministic (fixed) latencies. At 96 kHz operation (as adopted by Klark Teknik and Midas to minimise latencies when converting between analogue and digital domains), HyperMAC offers 192 bidirectional channels with an individual link latency of four samples, or 41.66 μs. In typical implementations, an additional latency of two samples is incurred converting to an internal data format such as I²S, to give a total of 62.50 μs. Currently HyperMAC only supports 96 kHz operation (support for other sampling frequencies will be added for the HyperMAC Software Development Kit release).
HyperMAC provides accurate phase-aligned clock distribution, utilising timing markers embedded in the data stream. This allows reliable, low-jitter clocks to be delivered to the end-points of the system. As digital audio systems develop into full networks from the current practice of connecting up isolated digital nodes using analogue cables, this ability to deliver high-quality clock signals with the audio will become increasingly critical.
The embedded clock allows HyperMAC to be transmitted over either Cat 5e/Cat 6 copper cable up to a distance of 100m as specified by the IEEE 802.3 Ethernet standard, or up to distances of 500 m using 50/125 μm multimode optical fibre.
Clock synchronisation is very simple to configure, units equipped with HyperMAC interfaces are either master (internally clocked) or slave (externally clocked). All that is necessary to create an operational audio network is to connect up the HyperMAC interfaces and select the clock source.
HyperMAC employs two levels of Cyclic Redundancy Check (CRC) for error detection, at the Ethernet frame level and at the audio data level. CRC checksums are calculated at the transmitting end of the link and sent with the corresponding Ethernet frames and audio data.
HyperMAC supports both dual redundant and N+1 redundant networking. Error and Link status information such as CRC error detection, clock synchronization status, link status and so on makes it very easy to provide health reporting to the user, and to implement redundant links with manual or automatic change-over.
HyperMAC has the in-built capability to relay control data, including TCP/IP and similar IP-based data packets, at a data rate of 200 Mbit/s. As a fixed capacity is allocated to the control data, there is no risk of the audio streams being swamped by control data messages. This is achieved by HyperMAC implementing separate control frames for the auxiliary data, distinct from the audio data frames. These separate control frames allow full Ethernet packets to be transmitted, allowing connection to a conventional Ethernet switch or router for the transmission of auxiliary data in TCP/IP format. The control data packet contents are therefore irrelevant to the operation of the HyperMAC audio streams, so any format of control message received can be relayed.