Widescreen_signaling

Widescreen signaling

Widescreen signaling

Aspect ratio signaling in an analog television signal

In television technology, Wide Screen Signaling (WSS)[1] 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.[2][3]

This development is related to introduction of widescreen TVs and broadcasts,[3] with the PALplus[4] system in the European Union (mid 1990s), the Clear-Vision[5][6] 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.[3]

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.

625 line systems

For 625 line analog TV systems (like PAL or SECAM), the signal is placed in line 23.[3] It begins with a run-in code and starts code followed by 14 bits of information, divided into four groups, as shown on the tables below (based on Rec. ITU-R BT.1119-2) :[7][8][9][10][1]

More information Bits (0 to 3), Aspect ratio ...

Note: The transmitted aspect ratio is 4:3. Within this area a 14:9 window is protected, containing all the relevant picture content to allow a wide-screen display on a 16:9 television set.

More information Bit, Item ...

525 line systems

525 line analog systems (like NTSC or PAL-M) made a provision for the use of pulses for signaling widescreen and other parameters, introduced with the development of Clear-Vision (EDTV-II), a NTSC-compatible Japanese system allowing widescreen broadcasts.[11][12] On these systems the signals are present in lines 22 and 285, as 27 data bits, as defined by IEC 61880.[3][13][14][15][1][16]

The following table shows the information present on the signal, based on Rec. ITU-R BT.1119-2 ("helper" signals are EDTV-II specific):[3]

More information Bit, Item ...

See also

References

  1. [1]
    APPLICATION NOTE 9716: Widescreen Signaling (WSS). Renesas. 1988.
  2. [2]
    Loncaric, Matej; Tralic, Dijana; Brzica, Maja; Petrovic, Juraj; Grgic, Sonja (September 17, 2009). "Managing mixed HD and SD broadcasting". pp. 79–82 – via IEEE Xplore.
  3. [3]
    RECOMMENDATION ITU-R BT.1119-2 - WIDE-SCREEN SIGNALLING FOR BROADCASTING (PDF). ITU. 1998.
  4. [4]
    "RECOMMENDATION ITU-R BT.1197-1 Enhanced wide-screen PAL TV transmission system (the PALplus system)" (PDF). itu.int.
  5. [5]
    FUKINUKI, Takahiko. "EDTV".
  6. [6]
    Pollack, Andrew (September 15, 1994). "Japanese Taking to Wide-Screen TV" – via NYTimes.com.
  7. [7]
    ETSI EN 300 294 - Television systems; 625-line television Wide Screen Signalling (WSS) (PDF). ETSI. 2003.
  8. [8]
    Battiato, Farinella, Puglisi (2011). IISFA Member book 2011 - Image/Video Forensics: Casi di Studio (PDF). IISFA. p. 8.{{cite book}}: CS1 maint: multiple names: authors list (link)
  9. [9]
    "All You Ever Wanted to Know About PALplus but were Afraid to Ask". Archived from the original on 3 March 2016.
  10. [10]
    "Fluke PM5420 Application Note PALplus" (PDF). assets.fluke.com. Archived from the original (PDF) on 3 March 2016. Retrieved 12 January 2022.
  11. [11]
    Nakayama, K.; Kojima, T.; Miyaguchi, H.; Sawaragi, T.; Yaguchi, Y. (August 5, 1995). "EDTV-II decoder by SVP2 (the 2nd generation of scan-line video processor)". IEEE Transactions on Consumer Electronics. 41 (3): 634–642. doi:10.1109/30.468089 – via IEEE Xplore.
  12. [12]
    "The Journal of the Institute of Television Engineers of Japan". www.jstage.jst.go.jp.
  13. [13]
    AN9716: Widescreen Signaling (WSS). Renesas Electronics Corporation. 1998.
  14. [14]
    RECOMMENDATION ITU-R BT.1298 - Enhanced wide-screen NTSC TV transmission system (PDF). ITU. 1997.
  15. [15]
    Kageyama, Masahiro (2010). Thesis Research on high image quality and high functionality of television (PDF).
  16. [16]
    Jack, Keith; Tsatsoulin, Vladimir (2002-09-11). Dictionary of Video and Television Technology. Gulf Professional Publishing. ISBN 978-1-878707-99-4.
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