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Widescreen signaling
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{{short description|Aspect ratio signaling in an analog television signal}} {{Use American English|date=June 2021}} In [[television]] technology, '''Wide Screen Signaling''' ('''WSS''')<ref name=":0">{{Cite book |url=https://www.renesas.com/us/en/document/apn/an9716-widescreen-signaling-wss |title=APPLICATION NOTE 9716: Widescreen Signaling (WSS) |publisher=Renesas |year=1988}}</ref> is digital [[metadata]] embedded in [[Vertical blanking interval|invisible part]] of the [[analog TV]] signal describing qualities of the broadcast, in particular the intended [[aspect ratio (image)|aspect ratio]] of the image. This allows television broadcasters to enable both [[Fullscreen (aspect ratio)|4:3]] and [[16:9 aspect ratio|16:9]] television sets to optimally present pictures transmitted in either format, by displaying them in [[Fullscreen (aspect ratio)|full screen]], [[Letterboxing (filming)|letterbox]], [[widescreen]], [[Pillarbox|pillar-box]], zoomed [[Letterboxing (filming)|letterbox]], etc.<ref>{{Cite web|url=https://ieeexplore.ieee.org/document/5342857|title=Managing mixed HD and SD broadcasting|first1=Matej|last1=Loncaric|first2=Dijana|last2=Tralic|first3=Maja|last3=Brzica|first4=Juraj|last4=Petrovic|first5=Sonja|last5=Grgic|date=September 17, 2009|pages=79β82|via=IEEE Xplore}}</ref><ref name="auto">{{Cite book |url=https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.1119-2-199802-I!!PDF-E.pdf |title=RECOMMENDATION ITU-R BT.1119-2 - WIDE-SCREEN SIGNALLING FOR BROADCASTING |publisher=ITU |year=1998}}</ref> This development is related to introduction of widescreen TVs and broadcasts,<ref name="auto"/> with the [[PALplus]]<ref name="auto2">{{Cite web |title=RECOMMENDATION ITU-R BT.1197-1 Enhanced wide-screen PAL TV transmission system (the PALplus system) |url=https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.1197-1-199802-W!!PDF-E.pdf |website=itu.int}}</ref> system in the [[European Union]] (mid 1990s), the [[Clear-Vision]]<ref name=":8">{{Cite web |last=FUKINUKI |first=Takahiko |title=EDTV |date=March 1991 |url=https://search.ieice.org/bin/summary.php?id=e74-b_3_540}}</ref><ref name=":13">{{Cite web |last=Pollack |first=Andrew |date=September 15, 1994 |title=Japanese Taking to Wide-Screen TV |url=https://www.nytimes.com/1994/09/15/business/japanese-taking-to-wide-screen-tv.html |via=NYTimes.com}}</ref> system in [[Japan]] (early 1990s), and the need to downscale [[High-definition television|HD broadcasts]] to [[Standard-definition television|SD]] in the US. The [[Bandwidth (signal processing)|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.<ref name="auto" /> A modern digital equivalent would be the [[Active Format Description]], a standard set of codes that can be sent in a [[MPEG transport stream|MPEG video stream]], with a similar set of aspect ratio possibilities. ==625 line systems== For [[625 lines|625 line]] analog TV systems (like [[PAL]] or [[SECAM]]), the signal is placed in line 23.<ref name="auto"/> It begins with a run-in code and starts code followed by 14 [[Bit|bits]] of information, divided into four groups, as shown on the tables below (based on Rec. ITU-R BT.1119-2) :<ref>{{Cite book |url=https://www.etsi.org/deliver/etsi_en/300200_300299/300294/01.04.01_60/en_300294v010401p.pdf |title=ETSI EN 300 294 - Television systems; 625-line television Wide Screen Signalling (WSS) |publisher=ETSI |year=2003}}</ref><ref>{{Cite book |last=Battiato, Farinella, Puglisi |url=https://www.dmi.unict.it/~battiato/download/IISFAMemberbook2011.pdf |title=IISFA Member book 2011 - Image/Video Forensics: Casi di Studio |publisher=IISFA |year=2011 |pages=8}}</ref><ref name="autogenerated2">{{cite web |title=All You Ever Wanted to Know About PALplus but were Afraid to Ask |url=http://stoneship.org.uk/~steve/palplus.html |archive-url=https://web.archive.org/web/20160303233323/http://stoneship.org.uk/~steve/palplus.html |archive-date=3 March 2016}}</ref><ref name="auto22">{{cite web |title=Fluke PM5420 Application Note PALplus |url=https://assets.fluke.com/appnotes/it_products/B0291A-16U9509_NL_EN.pdf |url-status=dead |archive-url=https://web.archive.org/web/20160303224309/https://assets.fluke.com/appnotes/it_products/B0291A-16U9509_NL_EN.pdf |archive-date=3 March 2016 |access-date=12 January 2022 |website=assets.fluke.com}}</ref><ref name=":0" /> {| class="wikitable" |+Group 1 - [[Aspect ratio (image)|Aspect ratio]] ! Bits (0 to 3) !! align="center" |Aspect ratio !! Picture placement inside the broadcast area !! Active lines |- | 0000 || - || align="center" |- || - |- | 0001 || [[Fullscreen (aspect ratio)|Full format 4:3]]|| align="center" |[[File:4_3_full.jpg|frameless|120x120px]] || 576 |- | 0010 || [[Letterboxing (filming)|Letterbox]] 16:9 top || align="center" |[[File:16 9 lb t.jpg|frameless|120x120px]]|| 432 |- | 0011 || - || align="center" |- || - |- | 0100 || Letterbox [[14:9 aspect ratio|14:9]] top || align="center" |[[File:14 9 lb t.jpg|frameless|120x120px]]|| 504 |- | 0101 || - || align="center" |- || - |- | 0110 || - || align="center" |- || - |- | 0111 || Full format 14:9 centre [[shoot and protect]] 14:9 (see note) || align="center" |[[File:4_3_full.jpg|frameless|120x120px]]|| 576 |- | 1000 || Letterbox 14:9 centre || align="center" |[[File:14_9_lb.jpg|frameless|120x120px]]|| 504 |- | 1001 || - || align="center" |- || - |- | 1010 || - || align="center" |- || - |- | 1011 || Letterbox [[21:9 aspect ratio|deeper than 16:9]] centre || align="center" |[[File:+16 9 lb.jpg|frameless|120x120px]]|| undefined |- | 1100 || - || align="center" |- || - |- | 1101 || Letterbox 16:9 centre || align="center" |[[File:16 9 lb.jpg|frameless|120x120px]]|| 432 |- | 1110 || Full format [[16:9 aspect ratio|16:9]] [[anamorphic]]|| align="center" |[[File:16 9 full.jpg|frameless|120x120px]]|| 576 |- | 1111 || - || align="center" |- || - |} ''<small>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.</small>'' {| class="wikitable" |+Group 2 to 4 !Bit !Item !Group |- |4 |Camera Mode ([[interlaced]]) / PALplus Film Mode ([[progressive scan]]) | rowspan="4" |2 - Enhanced Services |- |5 |Conventional PAL / PALplus [[PALplus|Motion Adaptative Colour Plus]] encoding |- |6 |No Vertical helper / PALplus Vertical helper present |- |7 |Reserved / [[Ghosting (television)|Ghost cancellation]] |- |8 |No subtitles / subtitles within [[teletext]] | rowspan="3" |3 - [[Subtitles]] |- |9 |No open subtitles / Subtitles in active image area |- |10 |Subtitles out of active image area / Reserved |- |11 |No [[surround sound]] / Surround sound mode | rowspan="3" |4 - Reserved |- |12 |No copyright asserted or status unknown / Copyright asserted |- |13 |Copying not restricted / Copying restricted |} ==525 line systems== [[525 lines|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.'''<ref>{{Cite journal |last1=Nakayama |first1=K. |last2=Kojima |first2=T. |last3=Miyaguchi |first3=H. |last4=Sawaragi |first4=T. |last5=Yaguchi |first5=Y. |date=August 5, 1995 |title=EDTV-II decoder by SVP2 (the 2nd generation of scan-line video processor) |url=https://ieeexplore.ieee.org/document/468089 |journal=IEEE Transactions on Consumer Electronics |volume=41 |issue=3 |pages=634β642 |doi=10.1109/30.468089 |via=IEEE Xplore|url-access=subscription }}</ref><ref>{{Cite web |title=The Journal of the Institute of Television Engineers of Japan |url=https://www.jstage.jst.go.jp/browse/itej1978/49/9/_contents/-char/en |website=www.jstage.jst.go.jp}}</ref>''' On these systems the signals are present in lines 22 and 285, as 27 data bits, as defined by [[IEC 61800|IEC 61880]].<ref name="auto"/><ref>{{Cite book |url=https://www.renesas.com/us/en/document/apn/an9716-widescreen-signaling-wss |title=AN9716: Widescreen Signaling (WSS) |publisher=Renesas Electronics Corporation |year=1998}}</ref><ref name=":15">{{Cite book |url=https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.1298-0-199710-W!!PDF-E.pdf |title=RECOMMENDATION ITU-R BT.1298 - Enhanced wide-screen NTSC TV transmission system |publisher=ITU |year=1997}}</ref><ref>{{Cite book |last=Kageyama |first=Masahiro |url=https://nagoya.repo.nii.ac.jp/record/12994/files/o6927.pdf |title=Thesis Research on high image quality and high functionality of television |year=2010}}</ref><ref name=":0" /><ref>{{Cite book |last1=Jack |first1=Keith |url=https://books.google.com/books?id=4Hsh7J0d1DwC&dq=%22Widescreen+signaling%22+-wikipedia&pg=PA147 |title=Dictionary of Video and Television Technology |last2=Tsatsoulin |first2=Vladimir |date=2002-09-11 |publisher=Gulf Professional Publishing |isbn=978-1-878707-99-4 |language=en}}</ref> The following table shows the information present on the signal, based on Rec. ITU-R BT.1119-2 ("helper" signals are EDTV-II specific):<ref name="auto"/> {| class="wikitable" ! Bit !! Item |- | 1 || Reference signal |- | 2 || Reference signal |- | 3 || Aspect ratio (4:3 full format / 16:9 letterbox) |- | 4 || Even parity for B3 to B5 |- | 5 || Reserved |- | 6 || Field type (First field / Next field) |- | 7 || Frame type (Reference frame / Other frame) |- | 8 || Vertical temporal helper (no / yes) |- | 9 || Vertical high resolution helper (no / yes) |- | 10 || Horizontal helper (no / yes) |- | 11 || Horizontal helper pre-combing (no / yes) |- | 12 to 14 || For TV station use |- | 15 to 17 || Reserved |- | 18 to 23 || Error correction codes for B3 to B17 |- | 24 || Reference signal |- | 25 to 27 || Confirmation signal |} ==See also== *[[PALplus]] *[[Clear-Vision]] *[[Active Format Description]] (AFD) *[[Teletext]] ==References== {{reflist}} == External links == *[https://www.renesas.com/en-us/www/doc/application-note/an9716.pdf Renesas AN9716, ''Widescreen Signaling (WSS)''] covering 625 lines and 525 lines standard. {{Video formats}} [[Category:Television technology]] [[de:Wide Screen Signalling]]
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