PAL/NTSC - chroma phase vs. colour documentation

From what I've read PAL is very similar to NTSC. It has a scheme with a com b filter that makes a phase (tint) control unnecessary, 50Hz frame rate rat her than 60 and a higher horizontal rate resulting in more lines in the ras ter. (your spelling says you are across the pond)

actually B-Y, which is blue without the Y component which is what the black and white signal is called here. For red there is Q for quadrature which i

al with the original phase does not affect the amplitude. Thus you get two discrete signals from one carrier. In the US it is 3.579545MHz which inhere ntly causes interlace, I imagine the PAL carrier, which I think is 4.43MHz accomplishes the same in PAL.

A vectorscope would give you the data. It is a bit easier to see when you h ave a phase control. You DO but it is not user adjustable because of the sy stem making undesirable phase shifts cancel each other out.

These color levels and phases are selected due to several factors having to do with visual perception. They also match the contour - for lack of a bet ter word - to the makeup of the Y signal. It is not 33%, 33%, 33%, it is ac tually mostly green. Thus the -Y for the green is the least precedent in co mparison.

The I and Q do not exactly match red and blue for whatever reason. They are a hair off, so many manufacturers went with a different demodulation angle

In the US the I signal is transmitted with a wider bandwidth and there are rare receivers that can use that. It requires an extra delay line. Also wit h that the only choice is true I and Q so whatever matrixing that has to be done falls on the engineer. Very very few units had that. I do not know if anything similar to that exists in the PAL system.

The bottom line is that I is blue and Q is red. Green was derived from thos e usually here, not demodulated itself.

I have worked (in the states) on some sets that had PAL capability but it w as mostly all in chips so further detail would have to come from a manufact urer training courses or the standards committee of the government.

So you may gloat that your analog color TV system was better than ours, how ever it is based on the same principles. Also your PAL, phase alternate by line system's one advantage depends on the comb filter, which I BELIEVE was invented or at least made practical by Sony for the color under home video recorder format.

But we had it first. And from what I heard the Russian system was the worst .

Now the French developed system called SECAM, I really have little to no id ea how that works. However the US was first and the government insisted on compatibility with the kagillions of black and white sets out there in use. I think PAL also has that capability but I doubt it with SECAM.

Still, we invented the dot matrix color CRT without which all this would be impractical. All color TVs would be projection of some type and that means three CRTs. We did use that scheme quite a bit for projection TVs but it t ook much better technology to accomplish it. I was one of the few who reall y knew the convergence (registration) circuitry in those things and that wa s my job for some time.

Form what I recollect, which means was told, the first color broadcasts wer e in the CBS system which was not compatible. Separate carriers for each of the three primary colors. Used on the moon. Funny now that we are back to that. What do you think is on them HDMI cables or comes out of the switcher ? Three channels, one for each color.

Anyway, the compatible NTSC system owes something to FM stereo which uses a very similar approach but no Q carrier.

In parts of Europe they used to call the NTSC system Never The Same Color b ut that was more due to engineers taking liberties with the accuracy of the

flesh tone. When the phase was a bit of the red and green wound up demodul ated differently and the phase shift affected the picture less. And their a ttitude was "Who cares if a wall is aqua or blue ?". They actually concerne d themselves much less with accuracy than with producing a picture pleasing to the eye. Sony was one major exception. Their attitude was to go for the accuracy and if the customer has to adjust the tint (phase) control so be it, but you KNOW if the wall is blue or aqua. It also got pleasing real qui ck like and other sets with all these liberties taken in the design started having their own "look". That was mostly brown and blue. When people saw t he Sony after watching all this faux color they liked the fact that it seem ed to have a better range of colors. It is like speakers in a way, if every thing sounds the same it is not high fidelity. That is the US forya. In fac t one manufacturer chose different phosphors for their CRTs to look better under the lights at a supermarket or big box store. Then you got it home an d like, ewwww.

The BBC bought up the rights to a bunch of Star Trek TNGs. I wonder if they got the original series. The test of a TV color system ? Is Spock green an d everyone else normal color ? I shit you not. they only put a little bit o f green tint on him so many TVs displayed the same color. Sonys, certain RC As, Zeniths, they were the main ones to give at least somewhat accurate col or rendition.

We had an RCA, one of the good ones - a CTC25 chassis.

Enough. This is probably more information than you wanted. (I am an expert on the NTSC system) But you can prove it all with the vectorscope. All you need to do is to find a way to vary the phase of the subcarrier a bit to se e what happens. It will come clear.

NTSC: Never Twice Same Color

SECAM: System Essentially Contrary to AMericans

PAL: Perfect AT Last.

Fuck you ! LOL

No offense intended, this time...

Colur encoding concept is the same.

It inverts phase every other line so that phase errors cancel each other out when summed.

:-)

Yes, the PM variant of QAM modulation is used in both. The differences are in frequencies and PAL error cancellation.

It was better in terms of colour fidelity and resolution. It was worse in terms of flickering, due to lower refresh rate and some el cheapo decoders being employed too often.

Instead of a variant of QAM modulation to encode U and V (I/Q) it sends the two in sequence, one per each line.

All three have. The requirement was the same everywhere.

[...]

Yeah, thanks - the thing is though: I can measure this with somewhat reasonable accuracy by sending pure R/G/B on to vectorscope and this will tell me how _does_ the generator encode the signal. What I am looking for though is the official/norm/standard specification telling how it _should_ encode it.

If chroma phase in reference to burst phase is the hue, what is the colour of 0 degrees, what angle should pure red, green, blue lie at in reference to the burst. You say "it's a hair off". Why so? Etc. Something like a real standard specification.

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SD!

omb filter that makes a phase (tint) control unnecessary, 50Hz frame rate r ather than 60 and a higher horizontal rate resulting in more lines in the r aster. (your spelling says you are across the pond)

r actually B-Y, which is blue without the Y component which is what the bla ck and white signal is called here. For red there is Q for quadrature which

gnal with the original phase does not affect the amplitude. Thus you get tw o discrete signals from one carrier. In the US it is 3.579545MHz which inhe rently causes interlace, I imagine the PAL carrier, which I think is 4.43MH z accomplishes the same in PAL.

have a phase control. You DO but it is not user adjustable because of the system making undesirable phase shifts cancel each other out.

to do with visual perception. They also match the contour - for lack of a b etter word - to the makeup of the Y signal. It is not 33%, 33%, 33%, it is actually mostly green. Thus the -Y for the green is the least precedent in comparison.

re a hair off, so many manufacturers went with a different demodulation ang

e rare receivers that can use that. It requires an extra delay line. Also w ith that the only choice is true I and Q so whatever matrixing that has to be done falls on the engineer. Very very few units had that. I do not know if anything similar to that exists in the PAL system.

ose usually here, not demodulated itself.

was mostly all in chips so further detail would have to come from a manufa cturer training courses or the standards committee of the government.

owever it is based on the same principles. Also your PAL, phase alternate b y line system's one advantage depends on the comb filter, which I BELIEVE w as invented or at least made practical by Sony for the color under home vid eo recorder format.

st.

idea how that works. However the US was first and the government insisted o n compatibility with the kagillions of black and white sets out there in us e. I think PAL also has that capability but I doubt it with SECAM.

be impractical. All color TVs would be projection of some type and that mea ns three CRTs. We did use that scheme quite a bit for projection TVs but it took much better technology to accomplish it. I was one of the few who rea lly knew the convergence (registration) circuitry in those things and that was my job for some time.

ere in the CBS system which was not compatible. Separate carriers for each of the three primary colors. Used on the moon. Funny now that we are back t o that. What do you think is on them HDMI cables or comes out of the switch er ? Three channels, one for each color.

a very similar approach but no Q carrier.

but that was more due to engineers taking liberties with the accuracy of t

to flesh tone. When the phase was a bit of the red and green wound up demod ulated differently and the phase shift affected the picture less. And their attitude was "Who cares if a wall is aqua or blue ?". They actually concer ned themselves much less with accuracy than with producing a picture pleasi ng to the eye. Sony was one major exception. Their attitude was to go for t he accuracy and if the customer has to adjust the tint (phase) control so b e it, but you KNOW if the wall is blue or aqua. It also got pleasing real q uick like and other sets with all these liberties taken in the design start ed having their own "look". That was mostly brown and blue. When people saw the Sony after watching all this faux color they liked the fact that it se emed to have a better range of colors. It is like speakers in a way, if eve rything sounds the same it is not high fidelity. That is the US forya. In f act one manufacturer chose different phosphors for their CRTs to look bette r under the lights at a supermarket or big box store. Then you got it home and like, ewwww.

ey got the original series. The test of a TV color system ? Is Spock green and everyone else normal color ? I shit you not. they only put a little bit of green tint on him so many TVs displayed the same color. Sonys, certain RCAs, Zeniths, they were the main ones to give at least somewhat accurate c olor rendition.

t on the NTSC system) But you can prove it all with the vectorscope. All yo u need to do is to find a way to vary the phase of the subcarrier a bit to see what happens. It will come clear.

We got the UK PAL system 10 years later than the US, it was effectively the mark 2 version of NTSC.

Re B&W compatibility, it was, but PAL colour was totally not compatible wit h the B&W standard it replaced. The older standard (adopted in the 1930s) w as 405 lines, positive modulation, VHF transmission and AM sound on a separ ate broadcast frequency. 625 line PAL was -ve video modulation, UHF carrier , embedded FM sound. For a while there were dual standard sets with a huge sliding switch that ran the length of the main PCB.

Re dot matrix tubes, there were previous non-projection systems that were n ever popular. There was the colour wheel, a 3 colour filter wheel than spun on front of a B&W CRT giving field sequential colour. And there was the sp inning mirror type, effectively an upgraded nipkov-esque system. That appro ach is still used in laser printers.

The first colour TV was nipkov type in the 1920s. Not a widley rolled out s tandard though.

'Never The Same Colour twice' was what I always heard. PAL certainly wasn't perfect but it was a significant upgrade.

Re colour setup, most PAL TVs were much the same but some sets were quite o ff. I never found out whether that was due to decoder or differing phosphor s. I remember a minority of sets giving a rather yellowy green in lieu of g reen - the overall result was a quite pleasant warmer picture but it wasn't accurate.

I designed an analogue NR system that was effective at addressing noise in dark picture areas, PAL's biggest shortcoming, but that was just before dig ital took over so went nowhere.

Delta tube sets typically didn't converge accurately. That marred resolutio n as well as giving miscoloured fringes. It did not look good. The Sony tub e really solved that. Also its higher output enabled more tinting giving be tter contrast as well as brighter picture. And less curvature meant less ge ometric distortion. Plus the Sonys were generally significantly lower video noise sets. OTOH early Sony colour sets used a throwback tuning knob, no c hannel preselectors. Sonys were also the only PAL sets I know of to have a tint control.

NT

Normally no, we didn't notice that. Or noticed but didn't complain about it because we didn't know that it could behave differently.

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SD!

NTSC predates Color TV. It stands for 'National Television Standards Committee'. It is from the very early days of electronically scanned TV in the United States.

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** Never Twice the Same Colour" is the acronym.

SECAM = "Something Essentially Contrary to the American Method"

MCAS = "Money Counts Above Safety"

..... Phil

Here you go:

But beware... My understanding is that the phosphors actually used in TV sets don't conform to the standard.

-- Adam

tle47-vol4-sec73-682.pdf

tle47-vol4-sec73-699.pdf

There are none that are an exact natch, but they have come a long way in the past 50+ years. The first could not render an accurate flesh tone, and the image was cartoonish. The first 'Rare Earth' phosphors helped a lot, a nd they have been tweaked over the following years.

Indeed. PAL and SECAM are acronyms for the description of how the systems work, and not for the organisation that devised the system.

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Ian

The refresh rate has nothing to do with the color standard (NTSC vs PAL), it is because of the different mains frequency in the countries that used the standard, and the advantage of approximately synchronizing the vertical refresh with the mains frequency on older receivers.

In Brazil, PAL is (was) used with the same refresh rate as was used for NTSC in the USA.

The different frame rate is not an attribute of PAL vs NTSC, but of the underlying B/W standard that was optimized for the local mains frequency.

PAL is used with ~60Hz frame rate in Brazil. NTSC with 50 Hz frame rate is possible, but there just happened to be no country where a 50 Hz mains frequency was in use and where NTSC color was selected.

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** Early tube based ( B&W ) receivers were locked to the supply frequency as were the local TV transmitters. This simplified PSU design and prevented hum bars rolling down the screen. Later this was changed to non locked. 60Hz was had an inherent problem cos it conflicted with frames rates used by film cameras. 50 Hz was far better since is was close to double the 24 fps rate used for movies - so on TV they ran slightly faster than in a cinemas. 60Hz TV has to use tricks (repeated frames) to play 24fps movies and can look jerky - even today.

.... Phil

True - refresh rate is defined in other standards, which define also number of lines.

see Rec. ITU-R BT.470-6 p. 2 That was an inaccurate mental shortcut from my side. Caused by the fact that I live on the other side of the pond, where "M" norm (525/60) you refer to wasn't used. OTOH NTSC isn't used with anything else than "M". This opens the trap I fell into and inaccurately combined PAL characteristics with non-M refresh rate/resolution, even if I myself corrected other people on occasions before.

Right - PAL/M

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SD!