Studio production recording
Dec 1, 2009 12:00 PM, By David Austerberry
Video servers are ousting the VTR, speeding turnaround and lowering costs.
BBC Ingex
In 2004, the BBC research department started some experiments to design and build a file-based acquisition system that would be based on commodity PC workstations. The project was to create a system that could replace VTRs for studio recording and provide automated shot logging. Dubbed Ingex, the project captured SD-SDI from the cameras and production switchers, and created MXF-wrapped DVCPRO50 files for subsequent craft editing.
The ingest workstation used a quad-core PC with four SDI video cards, and could capture and encode four simultaneous streams. Ingex is backed by a commodity NAS server, with 10TB of RAID storage on SATA disks. The start and stop time codes were recorded in a database and embedded in the MXF files. The production assistant could also add notes, naming scenes and takes, as well as comments like good or bad take. The Ingex application could also wrap multiple streams as an AAF file so the editor could drag multicam clip groups directly to bins in the NLE.
This work proved that servers could not only replace VTRs, but could also improve the efficiencies of the production processes with automation and enhanced metadata management.
Transmission servers
In production trucks, like this unit from Alfacam, production servers have become an essential part of the equipment.
Playout servers are a mature technology, but acquisition servers must operate at the higher data rates used in post production, rather than the somewhat lower rates used for a transmission files (typically 20Mb/s to 50Mb/s). For the editing process, popular codecs are 10-bit 4:2:2 with 220Mb/s data rates, which is five times the typical HD playout server data rates. The 10-bit resolution provides the necessary headroom for later color grading to match shots or give a production “look.”
Acquisition to a media server must be as reliable, or better, than videotape before a production company would consider changing its method of recording. The recording hardware platform must have sufficient computing resources to avoid missed frames under all possible conditions. Even with the improvements in CPU power and disk performance since the BBC experiments, HD data rates still require specialist hardware to provide the performance to support simultaneous recording, real-time replay and file transfers to other equipment. Many studio productions will want to process multiple parallel clips for multicam, or just multiple layers on the timeline, both requiring high bandwidth to and from the storage subsystem.
Any media production will also expect VTR-style features, like jog and shuttle, plus the ability to scrub through clips. It is possible to use a powerful workstation with a commodity video card to build your own VTR replacement server, but tweaking the system to meet key operational requirements, like the guarantee that frames will never be dropped, means that with today's hardware it makes more sense to use a proper media production server for studio operation.
The server manufacturers have taken a couple of routes in the design of production servers. One is to base the product on sports production servers. These already support more than is required; studio production doesn't need slo-mo replay of high-speed cameras.
The other approach is to build out the performance of playout servers to support the higher data rates. Future commodity workstations will have the bandwidths to support live acquisition with the absolute reliability that exceeds VTR performance, but shooting expensive talent is not the place to cut costs on technology. Missed shots through equipment malfunction are expensive in studio time.
Processes
The production server, together with the management application, provides not only the means to capture and process the media clips, but also extensive metadata management to aid production staff and to automate operations.
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