PAL vs. NTSC vs. SECAM

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Contents

Introduction To Analogue Television Colour Encoding

In order to broadcast television signals, transmitted over the air you will need two pieces of equipment, a television set with a receiver and an antenna to pick up the signal. Globally there are three systems in place, Pal, NTSC and Secam.

[1] NTSC (National Television System Committee) was the first to be developed in America in 1941. This first version dealt with a black and white broadcast only and in 1953 was revised to include colour. This was transmitted at 30 frames per second with each frame comprising of 525 scan lines.

[2] Pal (Phase Alternating Line) was introduced in the early 1960's in Europe. This had a frame rate of 25 frames per second and 576 lines. This system was used in western European countries (except France), Australia, parts of Africa,South America and Asia. The Pal format came in various forms, such as PAL B/G and PAL I. The majority of countries that use Pal have the standard 25 frames per second and 576 lines. The difference in different countries usually involve audio frequency and bandwidth.

[3] SECAM (Sequential Colour with Memory) introduced in the early 1960's in France, Russia, Eastern Europe and Africa. SECAM used the same resolution as Pal at 576 lines. It transmits the colour by forming the information ie. R-Y on one line and B-Y on the next.


Comparison

NTSC provides a smoother image than PAL and SECAM due to a higher frame rate. It used tint control to perform colour correction manually by the user. This was not always accurate and could lead to the colours being faulty. The PAL format uses phase reversal rather than tint control to cancel hue errors, this led to a far less saturated image. Further to this television engineers don't hold NTSC in high regard. SECAM was developed arguably to protect French television equipment manufactures and to make it more difficult to view non French programming. Unlike PAL and NTSC, SECAM television could not be edited in its original form, instead post production was done in PAL and the result trans-coded into SECAM at the point of transmission. Another area where SECAM is different is the transmission of blue and red colours, with PAL and NTSC they are send concurrently where SECAM sends them alternatively. This means SECAM removes colour artifacts but halves colour resolution.

Summary

  1. NTSC uses a refresh rate of 60Hz and SECAM uses 50HZ.
  2. NTSC has 525 lines while PAL and SECAM have 576.
  3. NTSC requires a tint control while PAL and SECAM don't.
  4. NTSC and PAL send the red and blue colour together while SECAM sends them alternatively.

Conclusion

Historically there has been two broadcasting standards, NTSC and PAL. Minor variations existed such as SECAM in France and was common to Eastern Europe prior to the fall of the iron curtain. The two major differences between the NTSC and PAL format are the frame rate and the number of video scan lines in a frame. In conclusion the system by which the signal is transmitted is different for each of the standards, what seems to be most important is the difference in resolution. NTSC has a lower resolution than PAL and SECAM, another reason PAL/SECAM images look so much beter is the wider and more accurate colour gamut they use. Taking these facts into consideration we feel that the PAL system provides the best technology for broadcasting, however these technologies are soon to be replaced by digital broadcasts.

References

  1. [4]iMovie '09 & iDVD '09 For Dummies by Dennis R. Cohen, Michael E. Cohen
  2. [5]Television Engineering and Video Systems By R G Gupta
  3. [6]Fundamentals of Television engineering by Glenn Milton
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