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What is the difference between NTSC & PAL ?
The National Television System(s)
Committee, the industry-wide standardization body created the
NTSC system. It is an analog television system used in Korea,
Japan, US, Canada and certain other places. An analog television
system is one which encodes signals (both picture and sound ) by
varying the amplitude and/or frequency of the signal.
The NTSC system for television uses a type of video signal
called the composite video signal in which the signals e.g. red,
green, and blue signals for picture and sometimes audio signals
are all mixed together. The NTSC standard is incompatible with
most computer video standards, which generally use RGB video
signals. To avoid consumption of extra bandwidth and improving
the picture quality of a video transmission a technique of
interlace is used .Interlace uses a scan technique which uses
fields (either odd fields or even fields.)
The NTSC system uses 29.97 interlaced frames of video per
second. Each frame contains 525 lines and can contain 16 million
different colors. The NTSC system interlaces its scanlines,
drawing odd-numbered scanlines in odd-numbered fields and
even-numbered scan lines in even-numbered fields. This yields a
nearly flicker free image at approximately 59.94 Hz per second
refresh frequency.
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Previously the refresh frequency was
exactly 60 hz in B/W television because the frequency of AC
power was 60Hz in the US. Then the refresh frequency was brought
down to 59.94 Hz to eliminate stationary dot patterns in the
color carrier. NTSC system has evolved from NTSC I to NTSC II to
NTSCIII. NTSCI has 525/60Hz system, NTSCII has 525/59.94 Hz
system and NTSC III is rigidly math defined.
PAL is short for phase-alternating line, phase alternation by
line or phase alternation line ,is a type of colour encoding
system used in many parts of the world. PAL was developed by
Walter Bruch in Germany and was first introduced in 1967.
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PAL delivers 625 lines at 50
half-frames per second as compared to 525/60Hz in NTSC. The PAL
colour system is usually used with a video format that has 625
lines per frame and a refresh rate of 50 interlaced fields per
second (or 25 full frames per second). This refresh rate of 50Hz
is used because Europe has a AC power standard of 50Hz.Flicker
is more likely to be noticed when using these standards. The
name PAL is used where the phase of part of the colour
information that exist in the video signal is reversed in each
line. This reversion automatically corrects the phase error that
occurs in the transmission of the signal by cancelling them out.
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Earlier PAL users had to rely on the
imperfection of the human eye to do the cancelling but that
resulted in a comb effect when the phase errors were strong.
Thus users use a delay line, it used to store the input and
deliver the output after a delay of a certain time(this time can
be in femtoseconds, nanoseconds, or microseconds). This reduces
the colour resolution compared to the NTSC system, but since the
human eye also has a colour resolution, this effect is not
visible. So PAL was also refferred as "Perfect At Last", "Peace
At Last", or "Pay for Additional Luxury" on a lighter note.
Even in PAL system , some countries have PAL M for ex in Brazil
where the system uses 525 line, 29.97 frame/s just as NTSC so
this is known as PAL M. The PAL colour system can also be
applied to an NTSC-like 525-line picture to form "PAL-60"
(sometimes "PAL-60/525"). This is often used in applications
such as playing NTSC video tapes on compatible PAL VCRs or
playing NTSC DVD-Video or video games.
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Motion pictures are typically shot
on film at 24 frames per second so when played back at PAL's
standard of 25 frames per second, films run 4.2% faster. However to
play it in NTSC it uses a method called 3:2 pulldown(The process of
converting 24 frame/s material to 29.97 frame/s is known as 3:2
pulldown) to convert the 24 frames per second to the NTSC frame
rate. This "3:2 pulldown" process creates a slight error in the
video signal compared to the original film frames.So, many movie
purists prefer PAL speed-up over NTSC's 3:2 pulldown, as the NTSC
results in a visual distortion due to 3:2 pulldown not present in
PAL sped-up video.
Both NTSC and PAL systems are incompatible with each other. So tapes
that are recorded in NTSC cannot be viewed in PAL systems and vice
versa. But there exists procedures by which they can be converted
and viewed. Without standard conversion, it is impossible to view a
video program that is recorded in a country with in US to be viewed
in Europe without first converting it.
NTSC 525/60
Lines/Field
Horizontal Frequency 15.734 kHz
Vertical Frequency 60 Hz
PAL
Line/Field 625/50
Horizontal Freq. 15.625 kHz
Vertical Freq. 50 Hz
PAL M
Line/Field 525/60
Horizontal Freq. 15.750 kHz
Vertical Freq. 60 Hz
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Article Contributed By: Namrata
Nayak
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