Your browser is out-of-date!

Update your browser to view this website correctly. Update my browser now


Route masters – audio and video routing, IP-based delivery and AVB

Broadcasters are increasingly comfortable with combined audio and video routing solutions, but what are the implications of IP-based delivery and AVB? David Davies reports

The concept of fully integrated solutions is one that is hard to escape these days, be it with regard to live audio or any manner of permanently installed applications. Broadcast is exhibiting the same trend, and an increasing number of operators are specifying combined audio/video routing solutions that would have seemed far-fetched even five years ago.

Hence, in TV, we find many broadcasters embracing video routers that accommodate SDI (Serial Digital Interface) with embedded audio and Dolby signals. “We are certainly seeing more and more people asking for the ability to mix within a single frame audio and video, and particularly to de-embed and re-embed, [as well] as to break out into AES and shuffle between levels with multi-language, multi-level audio,” confirms Alan Smith, product manager, routing & multiviewers at Snell.
 In radio broadcasting, meanwhile, IP-based delivery is at the top of the agenda when manufacturers discuss the general drift of routing technology.
 Part and parcel of making the various new approaches attractive to customers is the enabling of greater interoperability; many broadcasters, it is clear, simply do not wish to specify a one-brand solution for a complete workflow. Of course, not all developments are about the new – some, like ever-rising channel counts and redundancy requirements, are refreshingly familiar. And as Peavey Commercial Audio’s operations manager, James Kennedy, observes, “customers – particularly in the broadcasting sector – are always striving for lower latencies and higher quality audio”.
 In addition, it may be that the drivers of change are not entirely technological. On more than one occasion during interviews for this piece, PSNE heard references to a “generational” or “paradigm” shift taking place in broadcast, as a result of which tried-and-tested approaches are being reviewed afresh. Inevitably, given the prevailing financial climate, reducing cost is another important consideration, but above and beyond that, the onus is onflexibility – allowing customers to meet the requirements of a given project quickly and effectively.
Dedication: still what you need?

“Today, there is a clear trend away from classic dedicated audio interfaces towards new types of connectivity,” surmises Dr Klaus-Peter Scholz, one of the executive directors of Berlin-based manufacturer, systems provider and designer Salzbrenner Stagetec Mediagroup. As we shall see, radio is by no means immune to this development, but it is clear that the most dramatic changes are taking place in TV land.
 Historically, TV broadcasters would have faced a crucial decision when it came to purchasing a router as to whether they wished their facility to be an embedded or discrete audio plant. But recent technological developments have meant that it is possible to create a discrete audio facility utilising embedded audio – a development that has paved the way for the accommodation of video and audio routing in the same frame. The result has been a string of product launches that allow broadcasters to achieve this kind of combined routing solution.
 For example, Harris’ Platinum routers were designed from the start to enable single-frame routing of both audio and video signals. As Paul Greene, the company’s product manager for routing systems, reveals, a subsequent evolution has seen the implementation of a feature that enables the demultiplexing and multiplexing (‘demux’ and ‘mux’ for short) of audio signals within video streams.
 “This allows you to simplify design by enabling both embedded and discrete audio within the same frame to not only be routed but processed and manipulated,” elaborates Greene. “It makes design easier while providing significant cost, space and power savings.”
 By way of example, Greene alludes to a recent project at Elettronica Industriale in Italy that entailed an upgraded master control room built around five Platinum routers. The central router features a 512 x 512 configuration and is populated 400 x 400 with de-embedders on every input and embedders on every output, along with 32 x 32 mono analogue audio. Platinum’s mux/demux capabilities allow the router to process and route both discrete and embedded audio within the same frame. According to Harris, the 32RU system replaces approximately 230RU worth of equipment and runs at about 30% of the power required by the previous system.
 Salzbrenner Stagetec Mediagroup, meanwhile, has acknowledged the continuing trend towards high-definition video and 5.1 surround sound for TV with two of its latest developments: the XHDI 02 3G-SDI board and the family of Dolby E boards for NEXUS audio networks. Providing compatibility with every SDI format specified by the current standards, the XHDI 02 de-embeds, processes and re-embeds all the audio accompanying the video from and to the SDI stream. Combined with an XDED (neXus Dolby E Decoder) board, it is also possible to de-embed and decode Dolby E signals from the SDI signal, which can then be processed within the NEXUS system and re-endoded and re-embedded back into the SDI stream.
 “This procedure is even applicable to asynchronous SDI signals,” says Scholz. “As a further unique feature, the board has the ability to compensate for the delays inherent in the Dolby E decoding and coding process. This ensures that video and audio are always in perfect lip-sync.”
 To cite the aforementioned solutions is only to scratch the surface of currently available routing products. Ghielmetti is acknowledging the changes in broadcast routing with a product range that includes multiformat routers and routing/measurement equipment for embedded audio routing. Broadcom and Evertz also have extensive ranges, while Klotz Digital’s VADIS router is another popular choice, racking up more than 2,000 installations worldwide.
Addressing IP, AVB

Ultimately, a lot of these developments come down to flexibility and ease of integration, enabling the delivery of audio to wherever it may be required. And in this context, IP-based distribution seems eminently logical.
 “Ethernet IP audio transport is something that a lot of people are referring to in this context; ideally, you have your network IP switcher, all audio is routed real-time by the network, and it just works,” says Mikael Vest from NTP Technology, which has been manufacturing audio systems for broadcast since 1958. “That would be an ideal world, and the technology is definitely going that way, especially for smaller systems.”
 IP could also be part of providing a network interface to a large TDM routing backbone for a broadcast facility. “It could be that the connections are still MADI-based, for example, but with break-out connections also to IP interface systems,” suggests Vest.
 The momentum towards integration capability involving IP transfer is also readily acknowledged by Lawo, whose main focus has been on highly sophisticated audio networks since 1998: specifically, the provision of high-quality infrastructures and the implementation of efficient workflows for broadcast. For example, products such as the Nova73 HD router also support wide area networking for distributed remote locations.
 Against this background, the German company is also involved with the development of the RAVENNA technology, which provides a scalable, non-proprietary approach to real-time audio distribution that operates over conventional IP networks.
 “RAVENNA means for Lawo not only the [possibility] to transfer audio and control data on an IP basis, but also an additional dimension with regard to flexibility, compatibility and networkability of audio equipment of all kinds,” says Ulrich Schnabl, who is now executive assistant to the CEO at Lawo and previously served as product manager, routing systems. “At the same time it is important to say that we do not regard this development as a radical change. In fact, this change is a gradual process from today’s state-of-the-art technology towards a new level of flexibility and efficiency. Thus Lawo plans to adapt the benefits of the new technology step by step to existing products so that the users are benefiting where they need it.”
 Audio over IP solution provider Digigram – which patented EtherSound – is also mindful of the evolving requirements. Head of product marketing Pascal Malgouyard highlights the need for “flexibility of configuration” in numerous broadcasting applications, and points to the increased integration of IT and consumer requirements. “The adoption of major structural standards such as AVB (audio-video bridging) is a useful tool,” he suggests, “provided that these standards evolve rapidly to allow for strong interoperability between different AV manufacturers and the solutions they propose.”
 Indeed, AVB is an increasingly prominent presence on the landscape for audio routing suppliers; Salzbrenner Stagetec Mediagroup reveals that it will “soon offer an interface unit supporting this standard”. In a wider context – not exclusively related to broadcast – Kennedy says that “the consideration for AVB-compatible interfaces and products will be on the agenda for most [manufacturers], and the continuing wrestle between opting for open standards and/or developing proprietary solutions”.
Maintaining control

While new approaches to networking and distribution ultimately presage a greater flexibility of operation, the requirements for effective control will surely only increase as time goes by. The key, says Snell’s Alan Smith, is “not just to be able to do [what people want to do] within the router, but to be able to provide the control and status information about what is being done and how. For [Snell], this means that we are providing a lot more external intelligence with control systems and looking at the presentation of audio levels.”
 Contemporary broadcast applications tend to be highly complex, often prompting the use of a so-called global controller for overseeing intercom paths, audio and video links, and – increasingly – IP connections. “Entire control rooms, including their infrastructure and even external contribution lines, can now be assigned to a specific studio by just pressing a single key on such a controller,” says Stagetec’s Scholz.
 “This user-friendly way of delegating entire technical complexes has become increasingly significant with new installations during the past two years. Our systems – not only the NEXUS audio router, but also the audio mixing consoles (AURUS, AURATUS, ON AIR 24 and CRESCENDO) and DELEC intercom systems – integrate smoothly into such environments and are even capable of providing some of the automation features required.”
 Ease of integration with consoles, meanwhile, has manifested itself in an apparent resurgence of interest in the MADI digital audio distribution protocol (see PSNE September 2010). The technology’s non-proprietary nature and high-channel count have long made it a popular choice in broadcast, and new routing solutions supporting the standard continue to reach the market. For example, NTP recently added a 625 MADI router to its range. The 2,048 x 2,048 crosspoint router is packaged in a single 19″ 5RU frame with dual controller and dual power supply, and enables a total of 18 MADI cards with four MADI input and output interfaces to be accommodated. Each frame has a TDM bus capacity of 2,048 channels at 48kHz sampling rate, while it is possible to interconnect two frames using the NTP XBus connection for a total of 3,072 channels.
 “MADI has been around a long time, but what is driving [adoption now] is that it is no longer an expensive and complex interface to manufacture,” says Vest. “Mixer consoles very often have a MADI interface instead of AES or analogue, so the ability to connect directly to consoles is another issue.”

Audio routing for broadcast is approaching (or, perhaps, has already reached) an important crossroads, but this is far from the end of the story. The full implications of AVB are yet to become clear, while Stagetec’s Scholz highlights a separate issue – loudness metering – which the company is “certain […] will become a reality in the near-future. We are in close contact with the EBU working group, and a loudness-metering feature for our audio systems which complies with the EBU R-128 recommendation is currently under development.”
 Given the current pace of change, a generational shift in the broadcast sector perceived by some observers is arguably a welcome development. “Until now, a lot of people in the industry have had a background in analogue technology, and traditional digital technology; they came into the business during the ’80s or ’90s, and have been educated in one particular way,” believes Vest. “But, increasingly, I think that young employees at broadcasters do not have the same focus on the old-school method of broadcast technology, and are much more focused on the possibilities with IP and network systems, and computer networks in general. Consequently, I believe that, in the next five years or so, we will see more focus [on] IP-based audio and a [less strict] approach to routing in general.”