Clear-Vision is a Japanese EDTV (Extended Definition TV)[1][2] television system, introduced in the 1990s, that improves audio and video quality while remaining compatible with the existing broadcast standard.[1][3] Developed to improve analog NTSC,[4] it adds features like progressive scan, ghost cancellation and widescreen broadcasts. A similar system named PALPlus was also develop in Europe with the goal of improving analog PAL broadcasts.[5]

The initial version of the system was called IDTV[5] (Improved Definition Television,[6] or SuperNTSC[7]) and was based on advanced signal processing on TV receivers (allowing progressive scan and ghost cancellation),[6] without any extra information being broadcast. This system was studied in Japan by NTV,[8] under the direction of MPT (Ministry of Post and Telecommunications) and the BTA (Broadcasting Technology Association).[1][5]

EDTV-I (or "Clear-Vision") broadcasting began on NTV in August 1989.[8][1][5] Based on IDTV, a ghost cancellation signal is added to the transmission (to reduce the effects of multipath propagation), and NTSC luminance and chroma crosstalk are reduced by way of filtering.[6] This system was recommended by ITU-R BT.797 under the designation of "CLEARVISION".[9] Broadcast using this system ended on July 24, 2011.

EDTV-II[10][11] (or "Wide-aspect Clear-vision")[1][3] supports 480p[12] progressive scan,[13] wide-screen[14] and digital audio broadcasts. Tests started in 1994[15], with broadcast beginning in July 1995 by NTV.[8][16][17][5][2] The standard was published as ARIB STD-B9 - "Direct Coding for EDTV-II Television Signal" in 1997[18] and as ITU BT.1298 - "Enhanced wide-screen NTSC TV transmission system".[9]

EDTV-II broadcasts are displayed in letterbox format (with black bands on the top and bottom of the screen)[13] on 4:3 NTSC receivers without decoding. Information to reconstruct the original image signal is transmitted as helper signals - HH (horizontal high), VH (vertical high) and VT (vertical-temporal) - placed on the black bars.[19][9] This similar to PALplus,[20] a comparable system to improve analog PAL broadcasts. On EDTV-II compatible progressive or interlaced TV sets, broadcasts are seen on 16:9 wide-screen (with 480 line resolution).[9]

When introduced, EDTV-II was used on many shows by NTV such as Friday Road Show.[21] At the time of TOKYO MX[22] start in 1995, more than half of its broadcasts were in widescreen using EDTV-II, such as Tokyo NEWS.[21] Interest was predicted to be high, with manufacturers such as Sony and Mitsubishi having 16 to 32'' widescreen EDTV-II compatible TVs available that same year.[23][24] Yet due to lack consumer interest, broadcasts returned to regular 4:3 over the years. NHK used the system occasionally, as it was more interested in promoting its own analog high-definition MUSE system.[21] Widescreen EDTV-II broadcasts gradually disappeared, with World Heritage, broadcast by Sony, being the last shown using the format.[25]

Other than widescreen broadcasts, the system gave a limited improvements in image quality, mostly noticeable on larger TV sets. Yet these TVs benefited more from true HDTV broadcasts using the MUSE system, also available at the time.[5][26] With the introduction of digital broadcasts the system was replaced by ISDB broadcasts after 2012.

Technical details

The EDTV-II "Clear-Vision" transmission system is based on the following elements:[9][27]

Some elements are optional, but the standard requires that at least one helper and the wide-screen signaling are used.[9]

Aspect Ratio 16:9 letterbox
Active area 360 lines
Black area 120 lines
Horizonal Resolution 0 - 4.2 Mhz
Vertical Resolution 0 - 360 lines/height
Vertical High Resolution Helper (VH) 360 - 480 lines/height
Vertical-Temporal Helper (VT) 180 - 360 lines/height
Horizontal Helper (HH) 4.2 - 6.0 Mhz
Scanning 576 lines progressive / interlaced

See also


  1. ^ a b c d e FUKINUKI, Takahiko. "EDTV".
  2. ^ a b "HI-VISION TV IS GIVEN A LOW SURVIVAL RATING". Australian Financial Review. February 5, 1992.
  3. ^ a b Pollack, Andrew (September 15, 1994). "Japanese Taking to Wide-Screen TV" – via
  4. ^ RECOMMENDATION ITU-R BT.1118-1 - Enhanced compatible widescreen television based on conventional television systems (PDF). ITU. 1997.
  5. ^ a b c d e f "Digital Television in Europe and Japan" (PDF).
  6. ^ a b c JTEC Panel Report on High Definition Systems In Japan (PDF). U.S. DEPARTMENT OF COMMERCE. 1991.
  7. ^ Gerbarg, Darcy (January 31, 1999). "The Economics, Technology and Content of Digital TV". Springer Science & Business Media – via Google Books.
  8. ^ a b c "Corporate History". NIPPON TV.
  9. ^ a b c d e f RECOMMENDATION ITU-R BT.1298 - Enhanced wide-screen NTSC TV transmission system (PDF). ITU. 1997.
  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".
  12. ^ "525-line progressive scan signal digital interface standard and equipment". January 1, 1997: 141–146. doi:10.1049/cp:19971258 – via ((cite journal)): Cite journal requires |journal= (help)
  13. ^ a b Noble, Gregory W. (September 5, 2018). "Collective Action in East Asia: How Ruling Parties Shape Industrial Policy". Cornell University Press – via Google Books.
  14. ^ 紳一, 菊池; 光俊, 羽鳥 (July 9, 1995). "方式の標準化と審議経過". テレビジョン学会誌. 49 (9): 1117–1120. doi:10.3169/itej1978.49.1117 – via
  15. ^ "EDTV2 試験放送 画質評価用スライド放送" – via
  16. ^ "Telecompaper".
  17. ^ Masataka, Takahashi (July 5, 1996). "The Broadcasting Operation Of EDTV-II (Vide Clear Vision) Programs Especially Master Control Room". ITE Technical Report. 20 (3): 41–45. doi:10.11485/tvtr.20.3_41 – via
  18. ^ "About obtaining ARIB Standards (STD-B9)|Association of Radio Industries and Businesses".
  19. ^ a b Suzuki, N.; Fukinuki, T.; Kageyama, M.; Ishikura, K.; Yoshigi, H. (January 1, 1994). "Multiplexing scheme of helper signals on bars in EDTV-II": 32–36. doi:10.1049/cp:19940723 – via ((cite journal)): Cite journal requires |journal= (help)
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  22. ^ "TOKYO MX 開局の瞬間(199511)". September 20, 2015 – via
  23. ^ ANNUAL REPORT 1995 (PDF). SONY. p. 16.
  24. ^ "1995年懐かCM【三菱電機】" – via
  25. ^ "ソニー、TBS「世界遺産」スポンサー撤退 番組は継続". 朝日新聞. April 9, 2015.
  26. ^ Hart, Jeffrey A. (February 5, 2004). "Technology, Television, and Competition: The Politics of Digital TV". Cambridge University Press – via Google Books.
  27. ^ Kageyama, Masahiro (2010). Thesis Research on high image quality and high functionality of television (PDF).
  28. ^ CS4954/55 NTSC/PAL Digital Video Encoder (PDF). Cirrus Logic, Inc. 2006.
  29. ^ Multiplexing Scheme for Helper Signals in Top and Bottom Bars in EDTV-II. Journal of the Institute of Television Engineers of Japan. 1994.