DAVID Systems’ Video File Transfer system
May 1, 2009 12:00 PM, By Ingo Hahn
The German public broadcaster group ARD bases file transfers on MXF standards.
Following the successful introduction of digital workflows in radio broadcasting, ARD (the consortium of German public broadcasters) decided in early 2002 to implement digital exchanging of video content via a file transfer system. A working group was established by ARD's Production and Technology Commission (PTKO) to create a video file transfer (VFT) test system, to optimize this system for practical use, and to introduce the system into daily operations at ARD's broadcast networks and major studios. DAVID Systems was chosen as the development partner for the new video transfer project.
In early 2003, the German Institute for Broadcasting Technology, also known as IRT, and the PTKO's first participating broadcasters started trial operation of the system. Further broadcasters soon followed. Due to positive results from the test system, SWR (Südwestrundfunk “Southwest Broadcasting”) had already introduced several major VFT components into regular operations in 2004, integrating the numerous tapeless workflows across its regional and state studios. At this point, SWR was still using its proprietary video formats, which were fully integrated into the system. The next step was for the station management board to coordinate the required system optimizations with IRT and DAVID Systems and to jointly implement the MXF standard. Following certification of the MXF implementation, the VFT system was introduced into ARD's regular operations in October 2007.
System concept
Figure 1. An overview of the VFT system in place at ARD broadcast networks, stations and studios
Click to enlarge
ARD's broadcast networks, stations and studios employ a diverse range of production and playout systems, containing a wealth of different interfaces, formats and organizational structures.
In response to this complex structural framework, the VFT was conceived as an independent system for transporting and exchanging video content. Much like a head station, the system enables broadcasters to send and receive video files via a separate system layer. (See Figure 1.) All VFT data transmission takes place within ARD's proprietary HYBNET-based intranet.
The primary component of the VFT head stations is the replicator. This component (developed by DAVID Systems) interfaces with the ARD intranet for TCP/IP file transferring and monitors the transmission quality via confirmation messages. In the case of interrupted transmissions, transfers always resume at the point of interruption. Currently, transmission via the VFT is controlled manually, but the broadcast networks are already requesting a transfer scheduling option to transport large data volumes during noncritical and low-demand time slots.
Every file released to the VFT system for transmission has to conform to the ARD file specifications. This restriction addresses the multiplicity of file formats that are currently being used, as otherwise the time and processing power required for file conversion could seriously affect VFT system performance. The receiving stations import the files directly into their production systems according to the VFT specifications. It is entirely up to each station how and via which systems the files are converted before and after the VFT transfer. The station management board refrained from instating any restrictions on the level of the individual stations.
Currently, VFT file transmission is based on a “push” concept, which means that the sender station has to trigger the transfer of the requested files. The VFT system responds by immediately transferring the transmission file (the so-called “essence”) and its metadata to the receiver station. At the receiving end, essence and metadata are stored on a file server in accordance with the sender's specifications. The receiver station's production system then fetches the data from the file server via a Web service interface for further processing.
Compression formats
ARD's many different broadcast stations employ a wide variety of compression formats. In the development of the VFT system, therefore, the PTKO decided to include several formats for compression. Sending stations may freely select from any of the specified formatting options, with preference given to the in-house format. The receiving stations, correspondingly, only need to be able to decode the specified compression formats.
The VFT system permits the following compression formats:
- MPEG 422MP/ML, type D10 (SMPTE S356);
- DV/DV50 (SMPTE S314); and
- DV (including MiniDV and DVCAM).
Where pre-agreed, formats other than these may also be used.
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