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Widescreen signaling

From Wikipedia, the free encyclopedia

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.[1][2]

This development is related to introduction of widescreen TVs and broadcasts,[2] with the PALplus[3] system in the European Union (mid 1990s), the Clear-Vision[4][5] 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).

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.[2] It begins with a run-in code and start code followed by 14 bits of information, divided into groups as shown on the tables below:[6][7][8][9]

Group 1 (aspect ratio)

b00 b01 b02 b03 Aspect ratio Picture placement inside the broadcast area Active lines
0 0 0 0 - - -
0 0 0 1 4:3 full-height
4 3 full.jpg
576
0 0 1 0 16:9 letterbox top
16 9 lb t.jpg
432
0 0 1 1 - - -
0 1 0 0 14:9 letterbox top
14 9 lb t.jpg
504
0 1 0 1 - - -
0 1 1 0 - - -
0 1 1 1 4:3 full-height, framed to be "14:9-safe"
4 3 full.jpg
576
1 0 0 0 14:9 letterbox
14 9 lb.jpg
504
1 0 0 1 - - -
1 0 1 0 - - -
1 0 1 1 Letterbox deeper than 16:9
+16 9 lb.jpg
<432
1 1 0 0 - - -
1 1 0 1 16:9 letterbox
16 9 lb.jpg
432
1 1 1 0 16:9 full-height (anamorphic)
16 9 full.jpg
576
1 1 1 1 - - -

Group 2 (enhanced services)

b04 Mode (PALplus specific)
0 Camera Mode (interlaced)
1 Movie Mode (progressive scan)
b05 Mode (PALplus specific)
0 Standard PAL color
1 Colour Plus encoding
b06 Mode (PALplus specific)
0 No Vertical helper
1 Vertical helper present
b07 Ghost cancellation

Group 3 (subtitles)

b08 Mode
0 No subtitles
1 Teletext subtitles
b09 b10 Mode
0 0 No subtitles
1 0 Subtitles inside active image area
0 1 Subtitles outside active image area
1 1 Reserved

Group 4 (other)

b11 Mode
0 No surround sound information
1 Surround sound mode
b12 Mode
0 No copyright asserted or status unknown
1 Copyright asserted
b13 Mode
0 Copying not restricted
1 Copying restricted

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.[10][11] On these systems the signals are present in lines 22 and 285.[2][12][13][14]

The following table shows the information present on the signal ("helper" signals are EDTV-II specific):[2]

Bit Item
B1 Reference signal
B2 Reference signal
B3 Aspect ratio (4:3 / 16:9)
B4 Even parity for B3 ~ B5
B5 Reserved
B6 Field type (first / next)
B7 Reference frame (reference / other)
B8 Vertical temporal helper (no / yes)
B9 Vertical high resolution helper (no / yes)
B10 Horizontal helper (no / yes)
B11 Horizontal helper pre-combing (no / yes)
B12~14 For TV station use
B15~17 Reserved
B18~23 Error correction codes for B3-B17
B24 Reference signal
B25~27 Confirmation signal

See also

References

  1. ^ 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.
  2. ^ a b c d e RECOMMENDATION ITU-R BT.1119-2 - WIDE-SCREEN SIGNALLING FOR BROADCASTING (PDF). ITU. 1998.
  3. ^ "RECOMMENDATION ITU-R BT.1197-1 Enhanced wide-screen PAL TV transmission system (the PALplus system)" (PDF). itu.int.
  4. ^ FUKINUKI, Takahiko. "EDTV".
  5. ^ Pollack, Andrew (September 15, 1994). "Japanese Taking to Wide-Screen TV" – via NYTimes.com.
  6. ^ ETSI EN 300 294 - Television systems; 625-line television Wide Screen Signalling (WSS) (PDF). ETSI. 2003.
  7. ^ 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)
  8. ^ "All You Ever Wanted to Know About PALplus but were Afraid to Ask". Archived from the original on 3 March 2016.
  9. ^ "Fluke PM5420 Application Note PALplus" (PDF). assets.fluke.com. Archived from the original (PDF) on 3 March 2016. Retrieved 12 January 2022.
  10. ^ 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.
  11. ^ "The Journal of the Institute of Television Engineers of Japan". www.jstage.jst.go.jp.
  12. ^ AN9716: Widescreen Signaling (WSS). Renesas Electronics Corporation. 1998.
  13. ^ RECOMMENDATION ITU-R BT.1298 - Enhanced wide-screen NTSC TV transmission system (PDF). ITU. 1997.
  14. ^ Kageyama, Masahiro (2010). Thesis Research on high image quality and high functionality of television (PDF).

External links

This page was last edited on 18 July 2022, at 11:26
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