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This article may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. (November 2008) |
PAL-M is the TV system used in Brazil since February 19, 1972. At that time, Brazil was the first South American county to broadcast in color. Color tv broadcast began on September 1972 when The tv networls Globo,Tupi and Bandeirantes tv transmitted the Caxias do Sul Grape Festival. Transition from black and white to color was not complete until 1977. Two years later, in 1979 color broadcast nationwide in Brazil was commonplace
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Technical specification
In Brazil, PAL is used in conjunction with the 525 line, 29.97 frame/s system M, using (very nearly) the NTSC colour subcarrier frequency. Almost all other countries using system M use NTSC.
Why PAL-M
NTSC being the "natural" choice for countries with monochrome standard M, the choice of a different colour system poses problems of incompatibility with available hardware and the need to develop new television sets and production hardware. Walter Bruch, inventor of PAL, explains Brazil's choice of PAL against these odds by an advertising campaign Telefunken and Philips did across South America in 1972, which included colour test broadcasts of popular shows (done with TV Globo) and technical demonstrations with executives of television stations. [1]
Compatibility
PAL-M signals are identical to North American NTSC signals, except for the encoding of the colour carrier. Therefore PAL-M will display in monochrome with sound on an NTSC set and vice versa.
PAL-M is incompatible with 625-line based versions of PAL, because its frame rate, scan line, colour subcarrier and sound carrier specifications are different. It will therefore usually give a rolling and/or squashed monochrome picture with no sound on a native European PAL television, as do NTSC signals.
PAL-M systems conversion issues
PAL-M being a standard unique to one country, the need of to convert it to/from other standards often arises.
- Conversion to/from NTSC is easy, as only the colour carrier needs to be changed. Frame rate and scan lines can remain untouched.
- Conversion to/from PAL/625 lines/25 frame/s and SECAM/625/25 signals involves changing the frame rates as well as the scan lines. This is achieved using complicated circuitry involving a digital frame store, the same method used for converting between NTSC and the 625/25 standards. The fact that the colour encoding of PAL-M and PAL/625/25 is the same does not help, as the entire signal goes through an A/D-D/A conversion process anyway.
PAL 60
The PAL colour system (either baseband or with any RF system, with the normal 4.43 MHz subcarrier unlike PAL-M) can also be applied to an NTSC-like 525-line (480i) picture to form what is often known as "PAL-60" (sometimes "PAL-60/525" or "Pseudo PAL"). This non-standard signal is a cheap method used in European domestic VCRs and DVD players for playback of NTSC material on PAL televisions. It's not identical to PAL-M and incompatible with it, because the colour subcarrier is at a different frequency; it'll therefore display in monochrome on PAL-M and NTSC television sets.
Technological obsolescence
ABERT/SET tests
Before SBTVD, from 1999 to 2000, the ABERT/SET group in Brazil did system comparison tests of DTV under the supervision of the CPqD foundation.
The comparison tests were done under the direction of a work group of SET and ABERT. The ABERT/SET group selected ISDB-T as the best system among ATSC, DVB-T and ISDB-T.
The outdoor coverage of field-tests result in "Brazilian digital television tests" show that ISDB-T is most robust system in Brazil.
SBTVD
The analog PAL-M is scheduled to be supplanted by a digital high-definition system named Sistema Brasileiro de Televisão Digital (SBTVD) by 2016.
References
- ^ PAL Das Farbfernsehen; Walter Bruch/Heide Riedel; Deutsches Rundfunk-Museum 1987
See also
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