File-based workflows
Jan 1, 2008 12:00 PM, BY DAVID AUSTERBERRY
The technology opens entirely new and efficient ways to produce and air content.
File transport
The cost of long-haul telecommunications links has prevented the widespread use of file distribution for national or intercontinental distribution for broadcast-resolution files. Short items, like advertising spots, have been distributed by satellite or fiber for some time, but the distribution of programs has taken longer. To make a business case, fiber must be cheaper than conventional courier delivery of a videotape (along with costs of dubbing, QC and manual handling).
Fiber is gradually becoming an alternative to the courier, as telcos move toward Multi-Protocol Label Switching (MPLS) and away from the constraints of the digital hierarchies (PDH, SDH and SONET) designed for voice and data circuits. In many metropolitan areas, it is feasible to connect two premises with 1Gb/s fiber at a cost that makes the tape courier obsolete.
Alongside private networks, several companies offer digital media networks specifically designed for transport of video content. Typically the commercial networks use WAN acceleration to overcome the disadvantages of FTP. These two complete the missing link that connects the television production islands together.
Maximizing server cost/performance ratios
Figure 2. File interchange between broadcast production islands uses different resolutions. Three levels can provide a good compromise between cost and picture quality.
It would not be cost-effective to store a library of content on video servers. Video servers include integral coders and decoders, and they are designed for real-time operation. Therefore, video servers are unnecessary for general file storage. The most cost-efficient way to store video is on a hierarchy of storage, with the classic video server used for real-time ingest and playout, low-cost SATA/SAS arrays for nearline libraries, and data tape for backup and archive. (See Figure 2.) This concept is not new. Viewing copies were circulated as VHS tapes or DVDs before file-based workflows became commonplace.
To minimize the cost of servers, files must exist at different resolutions. Browse resolution can be stored online for instant access, and broadcast-quality archive files can be laid off to data tape. Playout server systems must be optimized to minimize the capacity needed to meet the demands of traffic. Long-GOP encoded files can be used to advantage in transmission. About half the size of the editable I-frame archive files, long-GOP files maximize the capacity (in program hours) of the more expensive video servers and can be transferred faster between the nearline and air servers.
If multiple resolution content files are used, media management must include transcoding engines. To maximize the potential video quality, the process pipeline for video files should minimize the concatenation of artifacts. The archive format is the benchmark, and that will set the best quality that can be achieved. Any other files will be derived from that, such as the long-GOP TX copies or low-resolution browse.
Selecting an archive format is an important decision. Ideally it should not be a lower quality than the acquisition format, but cost is always an issue.
Many broadcasters have adopted 50Mb/s I-frame 4:2:2 MPEG-2 (SMPTE D10) for SD content shot on DB. The data rate is less than half DB, but the increase in artifacts is considered minimal when compared with the cost-savings. Future archives for HD could be AVC I-frame, JPEG2000, or HDCAM (D-11). Who knows what is around the corner? It is all a balance between cost and quality.
Security
Tapes have several advantages when considering security. They are difficult to copy. To do so requires having two VTRs and the physical tape in your possession. Also, it is obvious if a tape is about to be over-recorded, as the record interlock must be switched — hardly an accidental operation. There is only one master tape, and it is relatively easy to keep track of clones. In contrast, it is simple to copy a file. It is also easy to overwrite a file.
The move to file-based production introduces many problems that never existed before. Take security. If you lose a tape, it may be inconvenient. And if a central file storage system gets corrupted, you have a major problem.
Tape systems are resilient to security breaches, a consequence of their dispersed nature and the physical nature of the recording medium. To many creative personnel, the adoption of the IT security measures found in banks can be an anathema. It is common to deliver graphics files or audio clips on USB sticks to an edit suite. Media organizations are learning the hard way that removable media can carry a computer virus, neatly bypassing an expensive firewall.
The physical tracking of tape using library software and bar codes has to be replaced with something much more complex for files. Regular IT practices of authentication of users (i.e. passwords) and authorization can prevent the copying or corruption of a file through access via the computer network. A user can be authorized to access folders and directories. The operating system (OS) will associate a file with the owner or user (usually the person who created the file), a group of users (project team, workgroup, department) or anyone with access (others). The file then has flags indicating who has permission to access the file, and who has read or read and write privileges. These flags can be set by “user,” “group” or “others.” For example, the archivist may have permission to write, which means they can delete the file. An editor may have permission to read a file, but not write. To edit, he or she would have to make a copy of that file.
DAM systems add much more to authorization, with support for fine-grained group definitions that can cater to different roles within a workgroup. They can allow for more flexibility when it comes to personnel, like the ability for a supervisor to override permissions if the user in on vacation, but the file must be processed immediately. This complex, role-based authorization gives the flexibility to use files in the broadcast environment, and extends that offered by an OS.
Aside from access and authorization, files must be protected against equipment failure. Backup procedures and RAID storage systems cover most of these issues. The other form of protection is to duplicate the main file archive at a remote site to permit simple recovery from a disaster like a bomb, fire or earthquake.
The level of backup and disaster recovery facilities is a balance between cost, convenience and the value of the content assets. If the archive is compromised, and it takes a day to retrieve a file from the disaster recovery site, then that may be acceptable. In master control, however, the backup must be available instantly.
Summary
File-based workflows offer many advantages to the broadcaster, including the potential to lower costs, enable collaboration and simplify multiformat publishing. However, a file-based workflow should not be dropped on existing systems without due consideration of the implications.
Staff members need training in a new approach to security, and IT procedures must reflect the level of threats. Media organizations will have to take precautions similar to those used by banks and government institutions. This is not easy, as media workers expect unfettered access to the Internet for research and communication. Plus, a great deal of file interchange is needed in the regular production workflows. Graphics and audio assets are frequently handled by different companies or departments from those handling the video. All gateways must be carefully designed to reflect the best security practices, but at the price point that the value of the content warrants.
The broadcast community is now in position to adopt files throughout the workflow from acquisition to delivery to the consumer. We have all the pieces to build the content layer — broadcast-friendly file formats, cost-effective contribution-quality file distribution networks, and secure management procedures.
The remaining issues are business and human. File operations need new, optimized workflows to realize the maximum cost-savings. These can be achieved through the use of methodologies like business process management. Television is set to join the enterprise business community.
| Want to use this article? Click here for options! |  |
