SECAM anyone?
 

I think all of us are familiar with NTSC and many of us are also familiar with PAL colour standards....but there is another major broadcast standard out there ....and it is rarely mentioned ....SECAM.

I know very little about it in practice ....although I have read technical articles I have never spoken with anyone with any practical experience of the system. It is as I understand it a form of line sequential colour system.

Given that it is in use in France and Russia and elsewhere there must be someone out there who has come across it in use!

Of course a quick study of DVDs coming from france is instructive ....they are all produced in PAL!

chris

I *think* PAL/SECAM are compatible - not sure what the difference is, as I think the frame rate/lines are the same. Certainly our blank VHS tapes in the UK used to (maybe they still do) state "PAL/SECAM" on them.

Indeed ...the 625 line / 50 field standard is used in most PAL and SECAM countries which means that at least the monochrome standards are compatible ...the difference is in the colour system ...with SECAM, I understand, the colour information is sent line by line with a delay line built into the receiver so that the colour information is never simultaneouly present in the signal.

The main problem seems to be to identify what is a red or blue line in the signal and this is done in a number of different ways depending on the version of SECAM employed.

since when does a blank tape care what tv standard you record on it :D

No idea - it's probably down to running time, since NTSC VHS runs the tape faster than PAL.

Here's a little more info on SECAM, courtesy of that "Behind the Tube" book-. Sez SECAM was proposed by the French partly out of chauvinism-imagine that- & partly to minimise color errors produced by inferior intrcity microwave transmission & eaely VTRs. As those systems have improved, SECAM's "advantages" have become irrelevant, & it does have some disadvantages. SECAM receivers are more complex, it's not easy to convert to PAL or NTSC, doesn't lend itself to special effects such as fades or lap dissolves. Finally, in the absence of signal distortions, it doesn't have the picture quality of NTSC or PAL. Ze French strike again...-Sandy G.

Back when I was working on a video tester, our goal was to support all standards. Yes, the SECAM standard is pretty strange. Few people know this, but the derivation of the SECAM name came from: Specifically Engineered Contrary to the American Method. In the end, there wasn't enough of a market of SECAM chips to warrent us making our tester compatible with SECAM.

The main thing about SECAM is that not enough information is supplied on each line for full color information. As I recall, the color information alternated per line. For example, one line has the green-red info, followed by green-blue, followed by green-red again, and so on. Now that I read that explanation, I think my memory from a project nearly 20 years ago is faulty.

More complicated with poorer performance (and reliability)? You sure the French didn't hire some British engineers? LOL Sure sounds like one of their cars.....come to think of it, sounds just like a French car too!

How the hell Europe stayed mobile for so many years boggles the mind. There's a saying in the old car crowd, the Brits worked on their cars all week so that they could drive them on the weekend, while Americans worked on them on the weekend so they could drive them all week!

Anthony

Yeah, sez here La Belle France was only able to browbeat the Russians & the Comecon countries, besides France themselves, into adopting SECAM. About everybody else went for Pal or NTSC. Way to go, jerkwads !! I'm sure ALL the big French electronics companies were working overtime for years turning out SECAM color sets for the ZILLIONS of affluent consumers in Romania, the DDR, Poland, Mother Russia...By God, we've got ze feelthy Americans on ze run this time, Pierre! Yes, Jacques, an' when ze Concorde comes on line in a few years, we gonna rule ze skies, too ! Boeing an' Mc Donnell-Douglas better watch out !-Fictitious French conversation about 1968...HehHehHeh...-Sandy G.

LOL....le belle secam
 

actually SECAM was designed like PAL to overcome the inherent phase problems of NTSC .....although the one technician I know who worked with SECAM (in France in the late 60s) said to me that in poor reception areas there were problems because the sets had problems identifying whether they were receiving a red or blue line...and the sets had no manual control to fix it!

But then early PAL sets suffered dreadfully from "Hanover Blinds" ....alternating bands of green and red as the set tried to sort out which line was in phase and which line was 180 degrees out of phase! (A problem only resolved by the use of a delay line in receivers...ironic because this was one of the reasons SECAM sets were more expensive ..which was one of the reasons PAL was selected in Britiain).

But I also know that the choice between the german developed PAL and French SECAM for Britain was a close run thing.

...of course I imagine chroma key etc would be a problem for CBS field sequential as well as SECAM ....

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SECAM uses an FM color subcarrier
 

SOme years ago I and another engineer had to design a digital chip to demodulate NTSC, PAL and SECAM. It's now the Samsung KSO127 if I recall correctly.

SECAM uses FM to modulate its color subcarrier. U is sent on one line, then V on the next, alternating. The receiver knows which is U and V as the frequency of the subcarrier is different for U and for
V. But unlike NTSC and PAL, the subcarrier amplude is constant, even in colorless areas of the picture. Not quite, they did another trick of reducing the amplitude at and near the subcarrier frequency, and letting it be higher for the higher sidebands. About 10 or so dB down at the subcarrier. Go any further and the FM demodulator loses it and you'd get noise. SO you always have cross chroma in the luma. Also any high frequency energy in the luma that happens to be near the chroma carrier can "capture" the FM demodulator and you get fake colors. There's also preemphasis of the U and V information at the encoder at the TV station and the demodulator needs to do deemphasis (cuts noise some, just like FM broadcast radio audio).

You can't separate the luma and chroma carriers too well. About the only thing you can do is notch out the spectrum around the chroma subcarriers. Comb filters wont work as the line to line correlation of NTSC and PAL isn't there.

Why did PAL take so long, anyway? Unless I'm missing something, save for the frame/line rates and the phase flip thing, isn't it just mostly a rip off of NTSC?

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That'll be the British way - too much red tape and wasted money. Tony Tit Blair is planning to axe a rather large amount of civil servants soon - and I can bet it WON'T be the inaffective middle management that goes - you know, those muppets that have brought our NHS to its knees...

As for British cars - we don't have many - they're either all GM, BMW or VW ;) I think there's only Morgan and TVR left now and I bet they're owned by the Japanese...

At least we can't lay claim to Citroen (ha ha ha!!!) or FIAT (Found in a tip). Or for that matter Ford (Fix or repair daily/found often at roadside dead). On that note though, I wish they'd bring back a 35 anniversary replica of the Mk1 UK Ford Capri - medallion man car yes, but there's something about it!

mmmm ....well as for PAL ....the development took some time ..and you are right it is essentially a development of NTSC designed purely to overcome the issue of phase error.

The concept of alternating phase line by line was in fact developed conceptually during the development of NTSC but proved impractical apparently.

It took Telefunken some time to iron out the problems and even they had serious issues, as I said above, with so-called "Hannover Blinds".

And what of the Lea Francis? Bet I just amazed you that a Yank knows about that marque! Someone recently obtained the rights to the name and has built at least a prototype but haven't heard anything more about it lately.

Personally, I prefer the Lotus Elise's styling. But one of my all time favorites would have to be the Lancia Stratos. I wonder if any of them were taped while rallying on a SECAM system (on topic content of this post LOL)

Anthony

Well, SECAM cames from "Sequential a memory". The sistem is working almost as PAL, but the colour signals are brodcasted one after another (first time the red color signal, after that the green colour signal, and last the blue colour signal). In PAL and NTSC the color signals are broadcatsed in the same time.
The USSR and the majorty of Eastern Europe countries (except former Iugoslavya and ROMANIA, which used PAL), adopted the SECAM standard beceause they didn't want taht the Western tv sets to work in their countyes. But, I heard that the West-German colot tv sets could also work on SECAM (I knew a few pesrons that had color tv sets before 1983, and they watched Bulgarian color tv programs that where broadcasted in SECAM).

By the way, the name of the guy that invented the SECAM color tv standard was Henry de France.
And also the French and the USSR SECAM standards where differnt.:blah:

Same w/NTSC. There are several different varieties of it. Everybody's gotta put their own little "tweaks" in, I suppose. I guess in all fairness to ze French, I should mention that PAL was developed largely for the same reasons that SECAM was-European pride & a chance to stick it in Sarnoff's & RCA's eye. PAL is not very different than NTSC, in fact, they were described as being members of the same generic family, Quadrature amplitude modulation. -Sandy G.

I do know there are variants of SECAM ....mainly to do with the way the color signal is polarised ..vertically or horizontally or something like that .... I believe...

as for PAL ...well PAL G, I etc ...tend to relate to the band allocation ...and sound offset... but are 625 line 25 frame

But then if I remember rightly is it Brazil that has PAL M....525 line 30 frame with PAL color and Argentina with 625 line NTSC?

eeek the variations are endless .....

If you try to put a SECAM signal to a PAL tv you'll get an black & white image.
The funny thing is that in Romanian "se cam" express a doubt.

if you do feed a SECAM signal to a PAL standard set you get B/W ....because the luminance signal for the two systems is pretty identical ...625line 50 frame ...the EBU standard agreed in the early 50s....the two systems just have differing colour standards .....:)

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When I was at Samsung doing the KSO127 NTSC/PAL/SECAM demod chip, it could tell PAL from SECAM. We designed a subsystem that measured the frequency of the subcarrier bursts. If 3.58 proceed to the test to tell NTSC 3.58 or PAL at 3.58; or if 4.42 then test for PAL 4.43 or NTSC at 4.43. If not those, and if you get 4.25 and (the other SECAM freq) on alternating lines, then its SECAM. We didn't look at the scan rates for this.

If the device only relies on the horiz and vert scan rates, then it can only tell NTSC from PAL/SECAM. It cant tell PAL from SECAM though.

Some multistandard consumer VCRs can produce a PAL signal at NTSC scan rates, or NTSC at PAL scan rates. Our chip didn't care as it only looked at the subcarrier bursts. So it could decode these non-standard standards.

my dvd recorder does a pretty good job of taking a PAL 625/50 input and creating a NTSC 525 /60 ouput....good enough to send friends in the US without problems either on tape or DVD ...extraordinary to think that this would have taken a room of tubes not so long ago! LOL

Came across this great article all about the various systems:
http://repairfaq.ece.drexel.edu/sam/tvfaq.htm#tvcts

I especially liked the following:
"SECAM stands for System Essentially Contrary to the American Method"

(The following is from: Robert Rolf).

SECAM:
Used by France and the former Soviet union.
No tint control. No color control.
Full socialism. The state knows exactly what color you
should see, and how strong that color should be.

PAL:
Used by Germany & UK, Australia etc.
No tint control. A color control.
Partial socialism. The state knows exactly what color you
should see, but you get a choice as to how strong it can be.

NTSC:
Used in USA and Canada, Japan etc.
A tint control, A color control.
Uncontrolled socialism. The state lets you chose what color you
see and how strong it can be. They then tax you regardless.

Anthony