The Geneva Audio Conventions
NEXUS as part of an automated workflow in TV broadcast
At first, it was only a notion in the minds of RTS technical staff. The vision of a fully digital, file based workflow for production and broadcast including consistent handling of all metadata from recording to archiving and combined with an automated, database driven system for converting all transmission material. The move to HD and the resultant technical revamp provided RTS with the ideal opportunity to realize this unique concept with NEXUS as a guarantor for broadcast-quality sound
Almost every STAGES presents at least one outstanding technical installation in Switzerland. It seems as if the particular circumstances in this relatively small country foster an especially innovative approach to professional audio and video! Perhaps it is the high mountains which make point to point radio transmission difficult which led to the very early introduction of fibre networks? Or maybe it is the different languages, four in number, for a total of only eight million inhabitants, that makes production and transmission of public radio and television a complex business? However, in this STAGES we once again dedicate ourselves to a Swiss installation: The new media and broadcast management system at Geneva based RTS (Radio Télévision Suisse) Swiss public TV and Radio which services the french speaking parts of Switzerland.
TSR, the RTS TV channels , are currently in the midst of a modernization project: The broadcaster is overhauling all of its production and transmission technical installations with the intention of being ready for HD. The project encompasses refurbishment of all production facilities, from the newsroom, to the sports studio, to the large production studios (each of these including HD control rooms) and – already completed – the central transmission areas housed in a new building. This new transmission centre is already partly on-air while the production studios will be refurbished step-by-step in the following years.
Yannick Dumartineix from RTS developed the digital audio technology concept for the new production and transmission centre in Geneva. About his experience with STAGETEC he says: »We use the NEXUS and the STAGETEC
technology because it is absolutely stable. That is very important for the playout site. The high quality audio is also another criteria.«
Files instead of physical media
With this project, the move to HD video goes hand in hand with the switch to an entirely file-based production workflow. As part of the project, SRG-SSR (the Swiss public broadcasting organisation RTS is a part of) introduced a new and mandatory audio format for on-air distribution. This company-wide standard describes precisely which audio belongs to a broadcast-quality video, where it is to be stored and in what format. The standard defines broadcast-quality stereo and 5.1 as mandatory for every video plus it requires an international audio mix – again in stereo and 5.1. While main broadcast audio at RTS is usually in French, the international mix audio is required for all non-french productions. In total, according to the standard, 16 native audio channels are mandatory. Even if there is no individual international mix or other language, something must be transmitted, even if it is only a duplicate of the french sound. Otherwise, for example, the original language channel would risk broadcasting without sound! The audio with two discrete stereo signals and two 5.1 signals in Dolby E® is then forwarded as one SDI stream to the broadcast distribution centre in Zurich together with the video.
The playout studio output signals are standardized strictly, but not so the input signals! Quite the contrary, on the input side almost all audio format combinations are possible. This is because the channel offers a wide variety of productions, ranging from home grown contributions and external productions to bought in feature films. Thus, audio signal conversion from the input format to the standard output format is necessary in most cases. For this purpose, RTS uses a single NEXUS Base Device, which is capable of converting almost automatically thanks to a clever logic control. This stand-alone Base Device is called the Audio Shuffler. It is controlled by the broadcaster’s playout automation system, made by French manufacturer SGT.
The internal workflow is based on the highly integrated interaction of several programs. Material for broadcast is checked in the newly built quality control area. An employee checks, amongst other things, which audio tracks are on the source tape and which mixes are on them (stereo or 5.1 or both). In addition, the loudness of the mixes is measured according to EBU recommendation 128. Currently, RTS aims for loudness levels of -23 LUFS which are the new Loudness Units. The measured value is stored in the RTS media asset management database which also stores other technical data about the material. Subsequently the checked video tape is digitised without any level changes and stored as a file in the central playout server.
As soon as a media is scheduled for broadcast, the media asset management system transfers the associated metadata to the automation playout system, including the status-quo of the audio tracks. At transmission time, the automation system has access to both parts of all pre-produced material, to the file itself and to its technical information, the metadata. When the material is played out for transmission, the automation system generates precise commands for the NEXUS Audio Shuffler. The system configures the NEXUS crosspoints in such a way that the NEXUS performs all the summing, up and downmixes, Dolby-E® decodings, delays and level reductions automatically. NEXUS perfoms the processing necessary on its internal DSP and Dolby-E® cards. When required, this automatic process can be overriden manually via a custom built control panel. In order to facilitate fading between two video signals, the Audio Shuffler is equipped with two identical processing units. And like the whole playout chain, the complete second Audio Shuffler works in parallel as a fallback option in case of failure, since the system performs its actions during live broadcasts.
The idea for the Audio Shuffler is certainly unique! The mass of detail involved in the implementation is down to a whole team. Apart from RTS as the client and STAGETEC as the supplier of the NEXUS Audio Shuffler, SGT as the source of the playout automation system, the general contractor and systems integrator BFE Studio und Mediensysteme Gmbh played a crucial role. In the meantime the concept has been implemented successfully a second time at RSI Lugano, the public Radio and TV broadcaster for the Italian speaking parts of Switzerland and discussions are in progress to roll it out across the entire Swiss TV broadcast landscape.
From production to archive
Tapeless contributions made by RTS, which are rapidly gaining ground, are produced right from the start in accordance with the standard audio format. Therefore, further conversion to match the standard is usually unneccessary. For older material on tape from the archive and for purchased material from external producers it’s a different story. This material has to negotiate the entire process from quality control to digitising and format adaption. It’s interesting to note that the material is archived without subsequent alteration. Who knows if loudness standards will be different one day in the course of technical progress? Strictly according to the rules of archiving, the levels of the original material are not altered but they are adjusted each time when broadcast, controlled by the metadata.
A big system
The Audio Shuffler is just one tiny element within RTS’s large production system. For all its complex automation, a 6U NEXUS base device plus an identical backup system is sufficient. But its range of functions and level of integration remains outstanding, even if its physical dimensions cannot compete with the much bigger STAGETEC installations found on the Geneva campus, encompassing three CRESCENDOs, several AURUS’ in the main control room and the HD trucks and – last but not least – a NEXUS audio network with almost 5,000 x 5,000 crosspoints networking the master control rooms and the new playout room. However, RTS has already begun to extend the Audio Shuffler’s range of functions still further by implementing stringent handling of Dolby D® metatdata for end-users, including a set of Dolby E® metadata profiles which then can be embedded through the NEXUS system. Such visions of the future are fun!
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