English NTSC TV's.

[Electronic M]

Here in NTSC-land I can see 60Hz flicker on CRT sets. It varies from unnoticeable to easy to see for me depending on the set and how fast my brain is clocking on a given day...I'm also more sensitive to it if I don't look straight at the screen. There have been times where I think I could actually just barely perceive the individual lines being scanned...

In the early 90's-DTV (the part of NTSC I've been alive for) color phase (tint/hue adjustment) tended to be fairly constant from station to station, and program to program, with some channels being slightly off from others occasionally (usually not not bad enough for anyone but knowledgeable videophiles/techs to notice enough to perhaps adjust the tint to compensate for).
However anecdotal evidence I've read/heard suggests that back in the tube era this was a more significant issue, and it was likely common in some places to have to tweak your tint knob on channel changes and some program source transitions. Tube equipment tended to suffer from adjustment drift, and it took many years for a vast majority of station techs to all learn how to keep their equipment calibrated properly...

[ppppenguin]

I hope we can take it as true that with reasonably modern broadcast kit and reasonable engineering standards both PAL and NTSC will give good results.

There are artefacts with both systems. Some relate to the udnerlying scan rates, others, such as lurid patterns on fine detail, are a side effect of the NTSC and PAL systems. These cross colour and cross luminance effects can be minimised by comb filter decoders which were much simpler on NTSC than PAL. Hence they were much more common in NTSC TVs. NTSC has lower chroma bandwidth so transitions between highly saturated colours are a little worse in NTSC. Readily seen on the green/magenta transition on colour bars.

PAL and NTSC have different dot crawl effects. These are primarily visible on monochrome sets. Since PAL subcarrier is a higher frequency they are probably less visible in PAL.

Phase errors should be minimal with decent kit and reasonable engineering.

Now wind the clock back to the early 1960s o even to the 1950s. It is obvious from the work at Hazeltine labs, Telefunken and others that colour phase problems were of great concern. NTSC broadcast kit needed a lot of engineering attention to give consistent colour and the TVs weren't much better. You needed a hue control which can readily be misadjusted by viewers. The idea of colour phase alternation as a solution to this was first raised at Hazeltine labs (c1955?) but was judged impractical then. CPA could be done on dot, line or field basis. The latter 2 were totally out of reach back then. Bruch picked up the CPA idea, did on a line by line basis and invented PAL.

At the time (late 1950s to mid 1960s) BBC engineers wanted to use NTSC and tried both 405and 625 NTSC systems. They reckoned they could wok to high enough standards to keep phase errors acecptable. Aided of course by much more modern kit than was available in the US in 1954. At the same time the french were pushing SECAM as a solution. Totally hideous in the studio and not really capable of being improved by better comb filters and suchlike. PAL was seen as the best answer AT THE TIME. Looking back, 625 NTSC would likely have worked perfectly well.

Hindsight is gloriously 20:20 vision. In the US the coming of NTSC brought the decision to offset the line and frame rates by a harmless fraction of a percent. To avoid moving the sound subcarrier by a similar amount. Who was to know back then the sheer amount of grief that would cause for broadcasters when timecode was invented. Grief that continues to this day as all the 1080 and 720 systems have widely used options for 59.94Hz and other field rates with a 1000/1001 offset.

The whole PAL/NTSC debate is now well behind us. For some years nobody (I'm sure somebody will find me an example of a small station in Africa that still uses PAL) has been producing new material in a composite format. High quality decoders are available to decode PAL and NTSC to their components with excellent results. Almost nobody is even radiating PAL or NTSC now.

[NewVista]

Originally Posted by ppppenguin

NTSC has lower chroma bandwidth..

Actually NTSC wider - 1.3m vs 1 m

With regards to monitoring in PAL-S...
Come to think of it, some monitors had PAL-S & PAL-D switch for convenient signal evaluation (clever).

[Penthode]

Originally Posted by NewVista

Actually NTSC wider - 1.3m vs 1 m

With regards to monitoring in PAL-S...
Come to think of it, some monitors had PAL-S & PAL-D switch for convenient signal evaluation (clever).

North American NTSC Receivers did not utilize the addition bandwidth for the "I" phase only. 500kHz for equal band decoding was the norm.

It is interesting that the new 625 line UK standard had wider bandwidth to accommodate full double sideband R-Y and B-Y. And the 625 standard the video - audio carrier spacing was set for NTSC so that the aural carrier would be an integer multiple of the horizontal scan frequency to facilitate proper chroma-luma interleaving.

[ppppenguin]

Originally Posted by NewVista

Actually NTSC wider - 1.3m vs 1 m

With regards to monitoring in PAL-S...
Come to think of it, some monitors had PAL-S & PAL-D switch for convenient signal evaluation (clever).

I think you are sadly misinformed. The IBA Technical Review Volume 2 (a reliable reference) specifies 1.3MHz (-3dB) point for PAL chroma. In System I countries the upper sideband is fully present on transmissions too. In System B/G countries it's a bit marginal.

SMPTE 170M(1993) gives more or less the same figures as for PAL but the USB isn't transmittable in a standard M channel. 170M notes the earlier NTSC standard where Q is 2dB down at 0.4MHz. A lot of NTSC coding has been done with narrowband 600kHz U/V axes rather than the complication of I/Q. This is discussed in SMPTE EG27. I would attach a copy but it's SMPTE copyright. Here's a quote from EG27:

The NTSC encoder described in ANSI/SMPTE
170M uses equal-bandwidth color-difference signals
(either B--Y and R--Y or I and Q). This removes the
need for a delay line in the color-difference signal. A
shorter delay line than required for NTSC 1953 is used
in the luminance (Y) signal (see figure 4).
When this signal is transmitted, a low-pass filter in the
transmitter bandwidth limits the luminance (Y) signal
and the upper sidebands of the color-difference sig-
nals (either B--Y and R--Y or I and Q) to 4.2 MHz.
Transmission of equal-bandwidth color-difference sig-
nals to the receiver has the effect of limiting the
recoverable chroma bandwidth to 0.6 MHz as a result
of the truncation of the upper sidebands of the chroma
modulation in the transmitter’s 4.2 MHz filter. This is
considered acceptable since there are no modern
receivers that utilize the theoretically possible wide-
band I demodulation made possible by maintaining

[NewVista]

Originally Posted by ppppenguin

. The IBA Technical Review Volume 2 (a reliable reference) specifies 1.3MHz (-3dB) point for PAL :

Snell & Wilcox paper contradicts this, claiming NTSC is wider - even saying many encoders maintain 1.3 for I & Q
http://www.snellgroup.com/documents/...des/edecod.pdf

__________________________________________________ ____________

"...there are no modern [NTSC]
receivers that utilize the theoretically possible wide-
band I demodulation.."

What about premium TVs like RCA 'Dimensia' (touted full chroma bandwidth in Ads), Pro-Scan, Sony 'Wega' and the incredible progressive scan Panasonic Xr-series?

[ppppenguin]

Strictly that's John Watkinson's paper, published by S&W. JW is a very well respected engineer here in the UK. His books include "The art of digital audio" and "The art of digital video". Both of these books are always to hand by my desk.

He covers historic practice as stated in the SMPTE docs and then correctly states that modern NTSC coders often use 1.3MHz chroma. This too is correct, my own designs do, as do many others. I don't bother to switch filters when changing between PAL and NTSC. This is fine in the studio. However the upper sideband of a 1.3MHz chroma signal will be heavily mauled by a system M transmitter. Strictly the coders maintain 1.3MHz for U and V, not I and Q. Though if U and V are both 1.3MHz, I and Q will be too.

Poynton, in "A Technical introduction to Digital Video" pp187-190, takes a similar view to Watkinson. He notes that SMPTE170M encourages the use of wideband (1.3MHz) chroma in the studio but also says that the practical broadcast chroma BW is only about 600kHz.

The subtleties of I/Q coding have been largely ignored in practice. Most broadcast coders simply encode on the U/V axes and bandwidth limit before the TX. Hence even a receiver with full chroma BW and I/Q demod will not find any benefit on virtually all material. Any claims like this are markting puff.

[NewVista]

Originally Posted by ppppenguin

Poynton,..says that the practical [NTSC] broadcast chroma BW is only about 600kHz.
.

Probably not surprising, but what is wrong with SSB for HF chroma components? as HF Luminance is SSB.

What would be ATSC chroma res (6mhz chnl) vs COFDM chroma res (in 8mhz chnl)?

[Penthode]

Originally Posted by ppppenguin

... The idea of colour phase alternation as a solution to this was first raised at Hazeltine labs (c1955?) but was judged impractical then. CPA could be done on dot, line or field basis. The latter 2 were totally out of reach back then. Bruch picked up the CPA idea, did on a line by line basis and invented PAL.

Actually CPA predated I/Q with no CPA (in the final NTSC standard). The benefit of CPA was realized early in 1951 and Hazeltine was initially indecisive whether to pursue Phase Alternate Line or Phase Alternate Field. At the last moment they opted to proceed with Phase Alternate Field because of the lack of a line delay for line averaging and field averaging by the human eye was preferred.

The NTSC originally pursued CPA because of limited bandwidth available for the interleaved chroma channel and CPA would facilitate R-Y/ B-Y full vestigial sideband operation with quadrature crosstalk cancellation. Unfortunately the electronic technology still had a long way to go to effectively use CPA and ultimately the vestigial sideband I and double sideband Q was adopted. The picture would have reduced chroma bandwidth but produced superior pictures at the time. The NTSC made the right decision when forty years later the electronic technology could more effectively use the standard and hue errors had become a thing of the past.

It is interesting to consider that 50's designed NTSC sets today display pictures consistently much better today than they did when they were new simply because the signal source now is consistently much better.

[wa2ise]

Originally Posted by ppppenguin

There are artefacts with both systems. Some relate to the udnerlying scan rates, others, such as lurid patterns on fine detail, are a side effect of the NTSC and PAL systems. These cross colour and cross luminance effects can be minimised by comb filter decoders which were much simpler on NTSC than PAL.

Back before about 1980 very few consumer TV sets had line combs. Just notch filters that assumed anything near the chroma subcarrier belonged to the chroma signal. Which made for the colored crawlies in referee's shirts and other luma fine detail. And few TV sets were able to display that fine luma detail anyway (above about 3MHz) as they low passed the luma to avoid showing the checkerboard chroma subcarrier pattern.

So if I ran a TV station back in the 60's and 70's, I would have low passed the luma to remove anything above 3MHz, and then mix in the chroma subcarrier, then transmit that. Thus producing much less artifacts on viewer's TV sets. People would say that my station looks cleaner... B&W sets made after NTSC color was introduced low pass filtered the luma as well, so those viewers would not see a lack of fine detail either.