Technical Spec

Structure
Not all screens are the same model. As a general rule the following specifications apply; all are LED screens, approximately 26 metres square and rising to a height of 10 metres or so above ground level. Some are free-standing on structural supports, others are attached to buildings. The screen operational hours vary from site to site, please contact us if you wish to know these details. Screens are RGB colour. Each is sited within busy, city-centre locations with the ability to host related events of varying sizes within the immediate space. This has varied from small, grassroots activity of no more than a dozen or so participants, to many thousands gathered for national broadcast events and sporting finals.

Audio
All screens without exception include audio playout. This is carefully monitored and set at levels that increase and decrease throughout the day, according to additional environmental noise and footfall. Most non-event playout is set to a level we term Ambient. Audio zoning is in operation so that excessive noise does not spill out in the vicinity of the screen, but is instead specifically targeted at the viewing area. Any video footage containing music or soundtrack must ensure this has been copyright cleared for use first. See document entitled Content Guidelines if further advice is required. Please pay careful attention to audio levels - if these are too high it may result in distortion during transmission.

Resolution
Generally, the screens possess less lines of resolution: less than a domestic digital television. It should be borne in mind that work including highly defined, hairline detail may not appear to its best effect. This also affects work that is very dark, as the screen is often in direct sunlight, while video pieces containing lots of delicate, shaded elements and little contrast do not appear to their best advantage. Scaling technology is in place to enhance perception, and a typical full-screen background image would normally be delivered at 720 x 576 (16:9), should you wish to use this as a guide.

Presentation
Screens are landscape in shape. Still images and artwork submitted in portrait form will result in blank areas to the left and right of the image. The alternative is to zoom in on the image, however this will result in a loss of detail and quality at the top and bottom. 
We mention this so that you might retain greater control over the presentation of your work.
Please note: material of any kind that has originally been intended for print or web will not automatically transfer to the screen successfully. Small, discreet typography does not always become clearer the larger it is projected, and handwriting styles are difficult to read. Keep it bold, clear, simple and uncluttered.

Screen Layouts
The Big Screens general layout is composed of four individual zones; a video window, city diary, weather zone and news ticker. During live events and special screenings the screens have the capability to show full screen live or MPEG video, there is also the option to have full-screen with scrolling descriptive text.

Plug ‘n Play
This refers to an access box, usually outdoors, in the form of a discreet weatherproof unit. Most screens have at least one at the base of the structure, while others have one or more additional units distributed across the city. Cameras, laptop computers or other forms of video/image generating equipment can plug directly into these in order to appear live on the screen. The connectors required are x1 BNC composite video and x2 XLR audio connections.
Please note: Some of the plug’n play points at the base of screens include an additional feed of the on-screen camera. Please contact each site manager for individual facilities.

Format
All video and animated material will be converted into mpeg format. We prefer to do this ourselves and ask that you submit using DV-Cam, Mini-DV or DVD. Please submit an SAE if you wish to have your work returned. Tapes/DVDs without and SAE will be held for 6 weeks only following final broadcast for personal collection - arrange with manager beforehand.

Video Optimisation
Width & height: 720 x 576
Audio settings: 48kHz, stereo
Data rate: 224 kbps

Document last updated 03/09/08 © BBC Public Space Broadcasting