Pass-through for DigiTurk
The Broadcast Systems division of Thomson Multimedia Broadcast has undertaken the design, systems management and installation of a DTH satellite broadcasting facility that delivers 120 channels of television and 38 channels of radio. The DigiTurk service reaches the population of the vast geographical area of the Eastern Mediterranean and extends to the Balkans, North Africa and even reaches into Central Europe.
Reinhard E. Wagner reports from Istanbul.
Istanbul -- In March of 1999 the Systems Group of Philips, which is now integrated into Thomson, was invited by Turkish telecoms group Digital Platform to a series of discussions, including a detailed briefing that set out the objectives of a project that required an installation providing up to 120 channels of television and more than 38 channels of radio delivered via digital satellite service. Primarily, it was for reception in Turkey but also included surrounding areas. Although its primary area of expertise was mobile telephony, not broadcasting, this new Digital Platform service -- DigiTurk -- would offer not only exciting programming opportunities but would also present innovative system architecture challenges.
Essentially, at the heart of the project was the client's intention to lease 10 satellite transponders, each with the capacity to transmit 12 TV channels. To fulfil this, a system was required to originate the programming.
The Broadcast Systems design team had to produce a basic plan, indicating the hardware and software that would be needed to originate all the channels, to manage the complex playout facility of multiple locally originated and compiled channels, and to keep operational costs down to realistic levels. This would certainly need a very high degree of automation both in the transmission and the monitoring of the signals.
The design team opted for a scheme that integrated a series of systems that brought together many of the techniques that the company had previously pioneered. These would allow multichannel origination under reliable, frame-accurate software control. Broadcast Systems found itself in the enviable position of starting this complex project completely from scratch with no pre-existing installation. The seven-storey building is located on the European side of the Bosporus, in the heart of Istanbul.
The installation comprised transmission automation hardware and software and also entailed developing interfaces to the Lysis TV control and management system. This interfaces to an external programme listing system for pass-through channels. Part of the success of the entire system was an extensive operational procedural relationship established with Lysis to ensure that the traffic control and scheduling system (TCS) interfaced with the automation component in an error-free environment.
Typically, not only is list management information downloaded into the playout automation system, but information is also automatically fed back to the Lysis system to confirm that material has actually been transmitted. This enables the management of the multiple intellectual property rights to be undertaken with ultimate accuracy and subsequently to generate the legally required paperwork.
The client originally intended to provide two different payment plans, which allowed viewers access to different groups of channels. The Philips' CryptoWorks conditional access system is an integral part of the transmission system. The conditional access system is closely integrated with the Lysis control and management scheme. The channels were categorised into two groups: first, channels originated on site from pre-recorded material and second, pass-through channels (local and international) received by microwave links and satellites and delivered to the viewer without alteration. These included the Turkish terrestrial channels, CNN and BBC World Service.
The video signal format throughout the station is serial digital video with all audio distributed digitally in AES/EBU. All alien formats received via external feeds or as a tape are converted into these standards.
A system design to handle all video signals digitally presents some choices. Ideally, all short-duration material should be stored on servers to eliminate possible errors (human and mechanical) that might otherwise be introduced using standalone tape or cart machines. And a server-based operation can be designed to run with fewer staff or even unattended for longer periods of time. However, the enormous amount of material to be stored in order to cope with 14 channels (on air 24/7) requires compression.
When using MPEG-2, the same compression could be maintained through the signal path to the transmission multiplexer, making it an ideal solution. The problem is how to insert interstitial material without decoding the MPEG stream first -- specifically, how to integrate separate programme elements stored in the MPEG format on the same server and provide a continuous programme output. Multiple decode and re-encode processes would be costly, introduce signal degradation and eliminate most of the advantages.
Thomson, in conjunction with EMC2, developed a system whereby a picture cut to new material in the MPEG data could be specified at any timecode without conventional MPEG restrictions. The resultant software permits the creation of a new I-frame at the cutting point, allowing the insertion of interstitial material entirely in the MPEG environment. This solution simplifies the design of the transmission chain for these channels and promises to become an industry standard, although created specifically to cater for DigiTurk's needs.
At the heart of the technical area are two identical EMC2 servers (main plus backup with mirroring). One of the 15 Venus routers in the system is used for content compilation, feeding the inputs of the servers from the outputs of a DigiBeta Flexicart and eight standalone DigiBeta VTRs.
At dedicated workstations all received material intended for transfer to the servers is identified and logged. After logging new content into the database of the Lysis traffic and scheduling system, the look-ahead capabilities constantly interrogate the transmission schedule, calling for material not already on the servers to be loaded from the input machines. A Thomson machine control system uses loading and playlists received from the TCS system and governs the execution of these tasks. Multiple clients for scheduling of the transmission playlists are distributed in the content department.
For channels running feature films and other long-format programmes, a more traditional approach is adopted using three DVCPRO cart machines. Each cart has two programme outputs from the five internal transports. Within each cart machine, two VTRs are assigned to one programme output, plus one for internal redundancy. In addition, two servers configured as time-delay units, plus several standalone tape decks, supply additional material under full-automation control. A Media Pool server with seven outputs provides the interstitial material for these channels.
Incidentally, resulting from the available capacity of the Media Pool, this server can also act as a backup system for the tape-based material played out from the DVCPRO cart machines. Both material loaded into the Media Pool server and the media management is undertaken by the Thomson automation.
ROUTING AND CONTROL
The pass-through channels are received on several dishes adjacent to the site and fed to banks of analogue and digital receivers. The L-Band feeds to these units are distributed through a fibre network with the satellite receivers arranged in pairs as main and back-up units. These can be remotely changed over from the master control room in the case of failure. The digital receivers provide up to two stereo AES audio outputs together with serial digital video. These outputs are split into two: one set of outputs feeding a monitoring router system and the others going via synchronisers to the main station router. This method of signal distribution and routing (operation and monitoring) is common throughout the station. The analogue receivers follow a similar path with analogue-to-digital conversion incorporated into the synchronisers.
In addition, the station's main router has two standards converters, a noise reducer and two aspect ratio converters to ensure that any type of received signals can be accepted and handled correctly. A Venus router (256x256 with digital video path and two digital AES paths) provides the main station routing. Additional Venus routers service the needs of the broadcast centre, including the tape format conversion operations, audio and video monitoring of the analogue and digital signal formats and monitoring of the MPEG-2 transport streams.
Thomson's Jupiter facility control system achieves control and supervision of the transport stream routers, the under-monitor displays, the audio detection units and the remote, manually operated VTRs.
A crucial component in keeping such a complex operation on air is the broadcast centre monitoring. Thomson's NetCaptain system is used to manage the overall monitoring. NetCaptain links via Ethernet to a whole range of software products to monitor each and every key area. Its Windows GUI provides operators with the status of all devices in a simple hierarchical view.
FROM A TO B
The first phase, system A,
was complete in just two months from start of installation to the handing
over in the middle of March 2000, whereupon the client took delivery of
55 operational TV channels and 22 radio channels. Making effective use
of statistical multiplexing on all transport streams, these channels are
delivered via five transponders. At the beginning of February 2001, system
B was handed over, extending the capabilities with the addition of a further
65 channels delivered via five additional transponders. From the original
concept to reality, it is clear that the system is capable of providing
all services that a state-of-the-art broadcaster currently would wish to
offer to its subscribers.