From: Bevis.King@ee.surrey.ac.uk (Bevis R W King)
Newsgroups: rec.video
Subject: TV Standards FAQ (First Public Release - Version 1.4)
Keywords: pal secam ntsc
Date: 9 Apr 92 14:52:46 GMT
Organization: University of Surrey, Guildford, Surrey, UK.

World TV Standards
(Revision: @(#)TV_standards	1.4 92/04/09 12:50:48)

This is a new document derived from the TV Systems FAQL I used to send
out.  It has become apparent that there are two distinct areas of concern
when dealing with the multitude of TV systems in use around the world;
that of which system is used where and what characteristics it has, and
the seperate problem of multi-standard video equipment.

This document covers the TV standards in use around the World.  It's
companion document, Multistandard Video Equipment, covers video equipment
that works in more than 1 standard.

All constructive comments gladly accepted.

INDEX:
SECTION 1.  Waffle: Why Do Different TV Standards Exist?
SECTION 2.  TV Systems:  The Basic Combinations with comparisons
SECTION 3.  Broadcasting System Details


REFERENCES:
For a copy of the companion document, Multistandard Video Equipment,
please email the author (B.King@ee.surrey.ac.uk).

For a more general FAQL on NTSC video systems and some general points,
see H Morrow-Long's FAQL - posted monthly to rec.video & VIDEOTECH -
the author's email address is: Long-Morrow@CS.Yale.EDU
(Copies of these FAQLs are available for anonymous ftp from CS.Yale.EDU
 [130.132.1.2, 128.36.0.3] in subdirectory pub/rec.video)

For a series of excellent introductions to LaserDisc, contact Bob
Niland: rjn@FC.HP.COM

SECTION 1.  Waffle: Why Do Different TV Standards Exist?

1.0  Eh?

	Not all the worlds TV receivers work in the same way.

	Different countries use different types of broadcast TV
system, most of which are to varying extents incompatible with
each other.

	Unfortunately, video recordings retain many of the characteristics
of the original signal of which they are a recording.  In general,
recordings are more likely to be compatible than recieving equipment,
but only with their own "family".

1.1  Why did this happen?

	Originally, TV receivers required a source of field timing signals.
Early set designers decided to use the Mains power supply frequency as this
source.  There are two Mains power frequencies widely used arround the World,
50Hz and 60Hz.  This immediately divided the worlds TV systems into two
distinct camps, the 25 frames per second camp (50Hz) and the 30 frames per
second camp (60Hz).

	Later the 60Hz camp made a small adjustment and changed the field
rate to 59.94Hz when they added colour to the signals.  The issue of field
frequency remained sufficently deep rooted in both TV standards that the
vested interest remained long after the original technical justification
had gone.

	The biggest compatibility problems between TV standards remain
related to the field rate; these are also the hardest problems to solve.
The first domestic machine to attempt to actually convert between the
two field rates was launched this year (Panasonic NV-W1), but at some
US$2600 retail price it is too expensive for most pockets.

1.2  Compounding The Problem

	Beyond the initial divide between 50 and 60Hz based systems,
further sub-divisions have appeared within both camps since the
inception of Colour broadcasting.  The majority of 60Hz based countries
use a technique known as NTSC originally developed in the United States
by a committee called the National Television Standards Committee.  NTSC
(often scurrilously refered to as Never Twice the Same Colour) works
perfectly in a video or closed ciruit environment but can exhibit problems
of varying hue when used in a broadcast environment.

	This hue change problem is caused by shifts in the colour sub-carrier
phase of the signal.  A modified version of NTSC soon appeared which
differed mainly in that the sub-carrier phase was reversed on each second
line; this is known as PAL, standing for Phase Alternate Lines (it has a
wide range of facetious acronyms including Pictures At Last, Pay for
Added Luxury (re: cost of delay line), and People Are Lavendar).  PAL has
been adopted by a few 60Hz countries, most notably Brazil.

	Amongst the countries based on 50Hz systems, PAL has been the
most widely adopted.  PAL is not the only colour system in widespread
use with 50Hz; the French designed a system of their own - primarily for
political reasons to protect their domestic manufacturing companies -
which is known as SECAM (the most common facetious acronym is System
Essentially Contrary to American Method).  SECAM was widely adopted in
Eastern Block countries to encourage incompatibility with Western
transmissions - again a political motive.

	In general, since the field and scan rates are identical,
you can expect to get a monochrome picture from a PAL video recording
replayed on SECAM equipment, and vice versa.  Transmission frequencies
and encoding differences make equipment incompatible from a broadcast
viewpoint.  Transcoders between PAL and SECAM, while often difficult
to find, are reasonably cheap.

	In Europe, a few Direct Satelite Broadcasting services now
use a new Colour System called D-MAC.  It's use is not wide-spread
at present and it is transcoded to PAL or SECAM to permit video
recording of it's signals.  It includes features for 16:9 (widescreen)
aspect ratio transmissions and an eventual migration path to Europe's
proposed HDTV standard.  There are other MAC-based standards in use
around the world including B-MAC in Australia and B-MAC60 on some
private networks in the USA.

1.3  It Gets Worse...

	In addition to the incompatibilities of 50 and 60Hz systems,
and the different Colour systems, there is a further barrier to
compatibility.  Fortunately, video recordings themselves are not
affected by this, only the equipment.  For various reasons of
number of stations and terrain, TV pictures can be transmitted in
any of three main frequency ranges, VHF, UHF and Microwave (Satelite
Direct Broadcasting).  Equipment designed to receive signals in only
one of these bands cannot receive transmissions in any of the other
bands.

	Further, there are differences between the encoding of
the sound between countries using the same frequency bands.  Within
50Hz PAL UHF transmissions, audio signals can be at 5.5Mhz offset
(system G), or at 6MHz offset (system I).  Similar differences exist
between the Middle Eastern versions of SECAM (MESECAM) and the Eastern
Block (OIRT) version.

1.4  ... and that's not all

	In addition to standard combinations of Scan Rate, Colour System
and transmission frequencies, there are further complications when it
comes to additional features like Stereo Sound, Sub-titling and information
services.  Fortunately, such differences do not effect the basic operation
of equipment conforming to the same broadcast standard, but they can
restrict the use of various features.

	In the cases of both stereo sound and additional textural information
carried in the top few lines of the picture, there are three competing
systems of varying technical merit.  The oldest still operational of the
stereo sound systems is the American MTS system based on NTSC transmissions,
only slightly more recent is the twin channel FM-FM system used in Germany,
Australia, the Netherlands and Switzerland.  The most recent system, Nicam,
has only been in existance for about 4 years, and ironically is still yet
to be fully implemented by its designers, the BBC.

	The oldest of the subtitling systems is almost definately the BBC
designed TeleText system which has been is use in the UK since the mid
1970s.  It is also the most widespread and the most flexible of the systems
in widespread use.  The US Closed Captioning mechanism came about through
political pressure from the Deaf organisations in the USA and has not been
developed beyond the simple job of producing subtitles for the Deaf.  The
French developed a subtitling and information system called Antiope which
has not found favour elsewhere, largely due to the existing widespread use
of the BBC developed TeleText system.  A few US stations have now adopted
the BBC-style Teletext and a few manufacturers, most notably Zenith, fit
the decoders to their sets.

SECTION 2.  TV Systems:  The Basic Combinations with comparisons

2.1  TV Picture Format/Colour System Combinations

Name      Frame/Field rate   Scan Lines    Colour System     Subcarrier Freq
----------------------------------------------------------------------------
NTSC      29.97/59.94        525           NTSC              3.58MHz
PAL-M     29.97/59.94        525           PAL               3.58MHz
SECAM-M   29.97/59.94        525           SECAM             ?
PAL       25/50              625           PAL               4.43MHz
SECAM     25/50              625           SECAM             4.25MHz/
D-MAC     25/50              625(1250)     D-MAC             N/A
HiVision  60/120             1125          HiVision          ?

2.2  A Comparison of the Relative Merits of TV systems

NTSC/525 Advantages:

 * Higher Frame Rate - Use of 30 frames per second (really 29.97) reduces
   visible flicker.

 * Atomic Colour Edits - With NTSC it is possible to edit at any 4 field
   boundary point without disturbing the colour signal.

 * Less inherent picture noise - Almost all pieces of video equipment
   achieve better signal to noise characteristics in their NTSC/525 form
   than in their PAL/625.

NTSC/525 Disadvantages:

 * Lower Number of Scan Lines - Reduced clarity on large screen TVs, line
   structure more visible.

 * Smaller Luminence Signal Bandwidth - Due to the placing of the colour
   sub-carrier at 3.58MHz, picture defects such as moire, cross-colour,
   and dot interference become more pronounced.

 * Susceptablity to Hue Fluctuation - variations in the colour subcarrier
   phase cause shifts in the displayed colour, requiring that the TV
   receivers be equiped with a Hue adjustment to compensate.

 * Lower Gamma Ratio - the gamma value for NTSC/525 is set at 1:2.0 as
   opposed to the slightly higher 1:2.8 defined for PAL/625.  This means
   that PAL/625 can produce pictures of greater contrast.

 * Undesirable Automatic Features - Many NTSC TV receivers feature an
   Auto-Tint circuit to make hue fluctuations less visible to uncritical
   viewers.  This circuit changes all colours approximating to flesh tone
   into a "standard" fleshtone, thus hiding the effects of hue fluctuation.
   This does mean however that a certain range of colour shades cannot be
   displayed correctly by these sets.  Up-market models often have this
   (mis)feature switchable, cheaper sets do not.

PAL/625 Advantages:

 * Larger Number of Scan Lines - more picture detail.

 * Wider Luminence Signal - placing of the colour Sub-Carrier at 4.43MHz
   allows a large bandwidth of monochrome information to be recorded than
   with NTSC/525.

 * Stable Hues - due to reversal of sub-carrier phase on alternate lines,
   any phase error will be corrected by an equal and oposite error on the
   next line, correcting the original error.  In early PAL implementations
   it was left to the low resolution of the human eye's colour abilities
   to provide the averaging effect; it is now done with a delay line.

 * Higher Gamma Ratio - the gamma value for PAL/625 is set at 1:2.8 as
   opposed to the lower 1:2.0 ratio of NTSC/525.  This permits a higher
   level of contrast than on NTSC/525 signals.  This is particularly
   noticable when using multi-standard equipment as the contrast and
   brightness settings need to be changed to give a similar look to
   signals of the two formats.

PAL/625 Disadvantages:

 * More Flicker - Due to the lower frame rate, flicker is more noticable
   on PAL/625 transmissions; particularly so for people used to viewing
   NTSC/525 signals.

 * Lower Signal to Noise Ratio - higher bandwidth requirements cause
   PAL/625 equipment to have slightly worse signal to noise performance
   than it's equivalent NTSC/525 version.

 * Loss of Colour Editing Accuracy - Because of the alternation of the
   phase of the colour signal, the phase and the colour signal only
   reach a common point once every 8 fields/4 frames.  This means that
   edits can only be performed to an accuracy of +/- 4 frames (8 fields).

SECAM/625 Advantages:

 * Stable Hues

 * Higher number of Scan lines

SECAM/625 Disadvantages:

 * Flicker (see PAL/625)

 * Mixing of two synchronous SECAM colour signals is not possible.  Most
   TV studios in SECAM countries originate in PAL and transcode prior to
   broadcasting.  More advanced home systems such as SuperVHS, Hi-8, and
   LaserDisc work internally in PAL and transcode on replay.

 * Lower monochrome Bandwidth - Due to one of the two colour sub-carriers
   being at 4.25MHz, a lower bandwith of monochrome signal can be carried.

SECTION 3.  Broadcasting System Details

3.1  TV Systems - Transmission Details

Code  Frames  Scan Lines  Frequency  Sound Offset  Modulation   Still In Use?
-----------------------------------------------------------------------------
A     25      405         VHF        -3.5MHz       Pos          No
B     25      625         VHF        +5.5MHz       Neg          Yes
C     25      625         VHF        +5.5MHz       Pos          Yes
D     25      625         VHF        +6.5MHz       Neg          Yes
E     25      819         VHF        +11MHz        Pos          No
F     25      819         VHF        +5.5MHz       Pos          No
G     25      625         UHF        +5.5MHz       Neg          Yes
H     25      625         UHF        +5.5MHz       Neg          Yes
I     25      625         UHF        +6.0MHz       Neg          Yes
K     25      625         UHF        +6.5MHz       Neg          Yes
KI    25      625         UHF        +6.5MHz       Neg          Yes
L     25      625         UHF        +6.5MHz       Pos          Yes
M     30      525         VHF        +4.5MHz       Neg          Yes
N     25      625         VHF        +4.5MHz       Neg          Yes
(Satelite Systems)
Astra 25      625         11GHz band +7MHz         Neg          Yes
BSB   25      625         12GHz band ?             ?            Yes
?     30      525         Ku-band    ?             ?            Yes
NHK   60      1125        Hi-Vision  ?             ?            Yes

3.2  Additional Features 

Stereo Sound:

	MTS - single channel consisting of channel difference signals
relative to transmitted mono audio track and sometimes a secondary audio
program such as a second language.   Uses a technique based on the dbx
noise reduction to improve the frequency response of the audio channel.
Among common uses of the Secondary Audio Program facility is the Descriptive
Video Service (video for the blind).

	FM-FM - dual carrier FM coded discrete stereo transmissions,
analogue.  Should be capable of bi-lingual operation under user
selection.  Audio characteristics better than standard mono soundtrack.

	NICAM - (full name: NICAM 728) Digital two-channel audio
transmissions with sub-code selection of bi-lingual operation.  Stereo
signals with specifications similar to Compact Disc are possible.
NICAM stands for Near Instantaneously Companded Audio Multiplex and uses
a 32KHz sampling rate which produces a data stream of 728KBits/sec.

Subtitling:

	CC - (full name: Closed Captioning) transmitted on line 21 of
NTSC/525 transmissions, contains subtitling information only.  CC has
no support for block graphics or multiple pages but it can support
8-colours and the use of an italic typeface.  Frequently found on
pre-recorded VHS cassettes and LDs, also used on broadcast.

	TeleText - an information service of 200-700 "pages" covering
a wide range of topics including TV Schedules, News, Financial Market
prices, Comment, Reviews, Concert & Theatre information.  Subtitles
are typically transmitted on page 888 in the UK, on pages 199/299/399
in Belgium and Holland, on page 150 in Germany and on page 777 in
Italy.  There are a number of variant character sets used, but the
encoding is identical and all English alphabet characters plus numbers
and most punctuation can be handled by any decoder.  Includes support for
8 colours, and limited block graphics, and selective revealing of underlying
TV picture.  Transmitted on a variable number of lines (specified in header
which contains basic information such as time, date and channel), starting
on line 12 and continuing for 7-8 lines typically.  Found on broadcasts
and some LaserDiscs; recording of TeleText signals is marginal on S-VHS,
almost impossible on VHS.

3.3  Colour & Broadcasting Systems by Country

Country           TV System     Colour System   Stereo System  Subtitles
--------------------------------------------------------------------------
Albania               B/G           PAL
Australia             B/G           PAL         FM-FM          Teletext
Austria               B/G           PAL
Azores (Portugal)     B             PAL
Bahamas               M             NTSC
Bahrain               B             PAL
Barbados              N             NTSC
Belgium               B/G           PAL         Nicam          Teletext
Bermuda               M             NTSC
Brazil                M             PAL-M       MTS
Bulgaria              D             SECAM
Canada                M             NTSC
Canary Is             B             PAL
China                 D             PAL
Colombia              M             SECAM
Cyprus                B             PAL
Czechsolvakia         D/K           SECAM
Denmark               B             PAL         Nicam          TeleText
Egypt                 B             SECAM
Faroe Islands (DK)    B             PAL
Finland               B/G           PAL         Nicam          TeleText
France                E/L           SECAM       -              Antiope
Gambia                I             PAL
Germany               B/G           PAL         FM-FM          TeleText
Germany (prev East)   B/G           SECAM
Gibraltar             B             PAL
Greece                B/H           SECAM
Hong Kong             I             PAL         Nicam
Hungary               D/K           SECAM
Iceland               B             PAL
India                 B             PAL
Indonesia             B             PAL
Iran                  H             SECAM
Ireland               I             PAL         -              TeleText
Israel                B/G           PAL
Italy                 B/G           PAL         -              TeleText
Jamaica               M             SECAM
Japan                 M             NTSC
Jordan                B             PAL
Kenya                 B             PAL
Luxembourg            B/G           PAL         -              TeleText
Madeira               B             PAL
Madagascar            B             SECAM
Malaysia              B             PAL
Malta                 B/G           PAL
Mauritius             B             SECAM
Monaco                L/G           SECAM/PAL
Morocco               B             SECAM
Netherlands           B/G           PAL         FM-FM          TeleText
New Zealand           B             PAL         Nicam          TeleText
Norway                B/G           PAL         Nicam
Pakistan              B             PAL
Peru                  M             NTSC
Philipines            M             NTSC
Poland                D/K           SECAM
Portugal              B/G           PAL
Romania               D/K           SECAM
Saudi Arabia          B             SECAM
Seychelles            I             PAL
Singapore             B             PAL
South Africa          I             PAL
Spain                 B/G           PAL         Nicam
Sri Lanka             B/G           PAL
Sweden                B/G           PAL         Nicam         Teletext
Switzerland           B/G           PAL         FM-FM         TeleText
Tahiti                KI            SECAM
Taiwan                M             NTSC
Thailand              B/M           PAL
Trinidad              M             NTSC
Tunisia               B             SECAM
Turkey                B             PAL         -             TeleText
Utd Arab Emirates     B/G           PAL
United Kingdom        I             PAL         Nicam         TeleText
USA                   M             NTSC        MTS           CC (+TeleText)
USSR                  D/K           SECAM
Venezuela             M             NTSC
Yugoslavia            B/H           PAL
Zimbabwe              B             PAL

Once again comments gratefully received.  Thanks to everyone who has
contributed towards making this list more acurate.  

-------------------------------- NOTICE --------------------------------------
This article is hereby placed in the public domain.  Please do attribute the
author when using the article or an extract from it.  Thank you.
------------------------------------------------------------------------------
Regards, Bevis.

Bevis R W King,                    | Email:  B.King@ee.surrey.ac.uk
Computer Systems Support Officer,  | UUCP :  B.King@uos-ee.UUCP
Dept of Electronic & Electrical    | Voice:  +44 483 300800 ext 2272
Engineering, University of Surrey, | Email list for European LaserDisc Users:
Guildford UK GU2 5XH.              | europe-ld-request@ee.surrey.ac.uk to join.
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