PALplus[1] (or PAL+) is an analogue television broadcasting system aimed to improve and enhance the PAL format by allowing 16:9 (or 1.77:1) aspect ratio broadcasts, while remaining compatible with existing television receivers,[2] defined by International Telecommunication Union (ITU) recommendation BT.1197-1.
[1] Introduced in 1993,[3] it followed experiences with the HD-MAC (high definition) and D2-MAC, hybrid analogue-digital widescreen formats that were incompatible with PAL receivers.
It was developed at the University of Dortmund in Germany, in cooperation with German terrestrial broadcasters and European and Japanese manufacturers.
[citation needed] A similar system, developed in Japan at the same time and named EDTV-II/ Wide-aspect Clear-vision, allows for 16:9 NTSC broadcasts.
[4][5][6][7][8] The MAC family of standards was adopted in Europe in 1983,[9] primarily for Direct Broadcasting by Satellite (DBS) services.
[10][9] In 1986, a new high definition broadcasting standard, HD-MAC, was presented, offering twice the number of scanning lines compared to PAL.
While not attempting to produce HDTV standards of quality, the new format was meant to improve PAL in the following areas: In the beginning, the task group consisted of the public broadcasting corporations of Germany (ARD and ZDF), Austria (ORF), Switzerland (SRG) and the United Kingdom (BBC and UKIB, United Kingdom Independent Broadcasters) together with the consumer electronics manufacturers Grundig, Nokia, Philips and Thomson.
[21] VCR manufacturers associated with the PALplus consortium were expected to launch updated VHS and S-VHS home recorders soon.
Evaluations, performed by ITU and EBU engineers in 1995-1998 concluded that the use of down-converted HDTV source material, as well as high-quality widescreen standard definition content, could be a significant benefit to the PALplus picture quality.
Moreover, the experts felt that PALplus would not be out of place in an HDTV environment at viewing distances equal or farther to four heights of a television set.
[dubious – discuss][citation needed] Pay-per-view channels such as those on Sky often broadcast in 16:9, but use a different standard that requires another kind of decoder.
As some of the repeaters of ERT's channels were fed via OTE (Greek public telecom provider) in uncompressed form over terrestrial links, and others via NOVA (Greece's only satellite platform) using MPEG encoding, Palplus wasn't available on all areas.
The heavy MPEG encoding on NOVA degraded WSS signaling and the additional information embedded in PALplus, making it undecodable.
[33][34] With the switch to digital television and anamorphic widescreen, the system was discontinued with the end of terrestrial analogue broadcasts in November 2006.
Therefore, PALPlus over terrestrial analog PAL broadcasts remained the only source of 576 lines widescreen TV in Portugal for many years.
[40] Other public regional stations (like Galicia's CRTVG) tested the format too, but after these trials the technology was dropped and 16:9 digital broadcasts were not introduced until 2007.
A PALplus receiver can use extra information hidden in the black bars above and below the image to fully recover the 576 lines of vertical resolution.
This means that a PALplus signal provides no extra horizontal resolution to compensate for the image being stretched across a wider screen.
The use of the colour subcarrier means these signals appear as very dark blue and yellow patterns on black bars on a regular 4:3 PAL TV set.
The PAL colour carrier is modulated making use of correlation between 2 fields, in order to give a cleaner luminance/chrominance separation in the PALplus receiver.