Widescreen signaling

In television technology, Wide Screen Signaling (WSS) is digital metadata embedded in invisible part of the analog TV signal describing qualities of the broadcast, in particular the intended aspect ratio of the image. This allows television broadcasters to enable both 4:3 and 16:9 television sets to optimally present pictures transmitted in either format, by displaying them in full screen, letterbox, widescreen, pillar-box, zoomed letterbox, etc.

This development is related to introduction of widescreen TVs and broadcasts, with the PALplus system in the European Union (mid 1990s), the Clear-Vision system in Japan (early 1990s), and the need to downscale HD broadcasts to SD in the US. The bandwidth of the WSS signal is low enough to be recorded on VHS (at the time a popular home video recording technology). It is standardized on Rec. ITU-R BT.1119-2.

A modern digital equivalent would be the Active Format Description, a standard set of codes that can be sent in a MPEG video stream, with a similar set of aspect ratio possibilities.

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