BUT how would 525/60 PAL look compared to 525/60 NTSC? How bad was phase error in broadcast tv?

And the reverse what would 625/50 NTSC be like?

Ironically I think in good broadcast conditions ..hardly any difference ...but what happens in less than ideal reception conditions with multipath etc issues?

And afterall the 50hz/60hz issue is related to power supply... and in 1950s not really a matter of choice for the television system.

Look at a PAL-S TV and you are looking at NTSC. Good project: Convert a PAL set to Simple decoder for evaluation.

I've seen very rare instances of gross phase shift causing purple or green flesh tone but only on a local religious channel that used U-matic tapes to air and it wasn't the fault of the U-matic but the old program that had faulty production/equipment - all semi-professional junk and no quality control techs.

If you want to see 525/60 PAL for yourself check the options menu in your DVD player. Some have an option to output 525/60 PAL when playing back NTSC encoded DVDs. This mode is compatible with most PAL only TVs while avoiding some of artifacting caused when then player converts an NTSC encoded disc to 625/50 PAL.

525/60 PAL is also output by most modified PAL Playstations and earlier consoles when playing NTSC games. I found I noticed the differences between PAL and NTSC far more when gaming. The artifacting, color bleed and dot crawl all seemed far worse in NTSC than PAL (same console, same TV, just switching between PAL and NTSC modes). I'm not suggesting that PAL is completely immune to any of these defects, just that they aren't as severe. Ultimately for gaming go with direct RGB wherever possible.

I've had several 100Hz line doubled TVs. Some are better than others. Generally it's a softer smoother image, but the line doubler itself causes artifacts that are painfully obvious. Perhaps only painfully obvious when sitting too close and gaming, but at the time it was enough to downgrade from a 34" 100Hz set to a 29" 50Hz set.

Actually PAL has hideous dot crawl, it's one of its worst aspects. Research it, it's an amazing stuffup. Also DVDs don't have NTSC encoding so no NTSC to see.

Edit: Your multistandard PAL/COFDM optimized TV probably didn't have an NTSC comb filter - or even a notch filter - in analog mode.

I'm thinking of the Simple-PAL set again as a detector for difΦ in the broadcast chain: just look for the Hanover Bars. Anyone done this, comparing different broadcast conditions? If it happened a lot, it would vindicate the need for PAL or SECAM systems.

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...

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.

Don't you just wish the Beeb had decided to go with 405 line NTSC in 1956... all those glorious shows we might have in colour!

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.

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.

The pseudo PAL generated by a DVD or video game will still have the 4.43MHz color subcarrier. True 525/60 PAL would have a 3.57 or thereabouts color subcarrier.

[QUOTE=dr.ido;3114384]If you want to see 525/60 PAL for yourself check the options menu in your DVD player. Some have an option to output 525/60 PAL when playing back NTSC encoded DVDs. This mode is compatible with most PAL only TVs while avoiding some of artifacting caused when then player converts an NTSC encoded disc to 625/50 PAL.

Yes, I'd forgotten about the subcarrier. I guess that leaves models that actually have an option for PAL M for the country or two that uses (used?) it. Or a couple of consoles that had to have a 4.43MHz crystal fitted to output PAL.

Either way the end result is probably more comparing consumer encoder ICs rather than comparing PAL and NTSC themselves.

I guess the closest to seeing real NTSC for those of us who have never been to an NTSC country would be an NTSC Laserdisc? They're analog NTSC composite on the disc itself?

Just watching a Poirot in glorious NTSC on my "kerbside" find 1990s Panasonic. The set handles NTSC from DVD well via composite... but my technical knowledge is limited on the exact form of signal produced off the DVD player.

I have set the player up as if it is connected to an NTSC set. The Tint control becomes active and screen logos change size etc. And the TV set requires changes to brightness and contrast to reflect the change in black level.

And the reds change!

If I was watching PAL, I'd modify the decoder for PAL-S (the way Telefunken originally intended it) that way you would get back the vert chroma resolution the delay line robs you of!

A color system should really not give the public a 'Tint' control because its set up really requires a test signal. Even my 1954 GE hides the "Hue"(Tint) on the back panel (not sure if that was a good idea back then) but my mid 60s RCA has it on the front panel with no "correct-setting"detent (as all-tube chassis not stable enough for this?).

As I understand it DVD video is an MPEG2 stream which decompresses into digital component. The player encodes this as NTSC or PAL depending either on the flags set on the disc itself or the user settings. Most players default to auto and set the output according to the disc. Most players also have settings to override this and output either PAL or NTSC for all discs.

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:

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?

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.

The system as a whole was not stable enough in the all-tube era, a lot of it being traceable to distortions that occurred in amplifiers along the way and were taken out of the burst but not the chroma when clean burst was reinserted. Also, tube sets generally had less accurate burst gating and could be more sensitive to ghost conditions, channel tilts, etc.

It is worth noting that differences in color vision among viewers with normal color discrimination can account for up to a +/- 20% difference in the ratio of red and green to get a yellow and therefore a corresponding difference in flesh tone matching. This probably should be corrected by an adjustment to white balance for each viewer, but has never been contemplated because:
1) you can't do this for different simultaneous viewers; and
2) you would never be able to teach non-technical viewers how to make this adjustment.

Even with the white adaptation that occurs in all viewers, they will still see differences in flesh tones, and a hue control lets at least one person in the room compensate the rendition for his/her vision.

See:
A study of the need for color controls on color TV receivers in a color TV system operating perfectly, Hirsch, Charles J. ; Radio Corporation of America, Princeton, N. J., Broadcast and Television Receivers, IEEE Transactions on (Volume:BTR-10 , Issue: 3), Nov. 1964, Page(s): 71 - 86

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.

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)?

All receivers have DSB demodulators for chroma. I haven't done the sums nor have a reference to hand to say what happens when you feed them with a SSB or VSB signal.

ASTC chroma vs COFDM chroma is almost an irrelevant question. Assuming we're talking about standard definition the input to the coder is in each case a standard "601" 4:2:2 signal as defined in SMPTE125M or its Eurpopean eqivalent. The output of the decoder is in the same format. The maximum possible chroma BW is 3.75MHz with a brick wall filter. This is followed by data compession using MPEG. This usually involves subsampling the signal to 4:2:0.

Finally we get to the significant difference between ASTC and DVB, the channel coding. 8VSB for ATSC and COFDM for DVB. Without going into the differences between them or the arguments this has caused it's just a method of carrying a certain bit rate reliably from TX to RX. It has no influence whatsoever on Y or C BW.

Apart from the likely decimation of chroma on the vertical axxis to make 4:2:0, on still pictures what comes out will be very close to what goes in. Any artefacts will depend on how heavily you compress the data. Such artefacts will not normally include any loss of BW. For moving pictures there are additional artefacts which may become visible if too much comrpession is used. Again loss of BW just doesn't happen.

Failure of the channel coding produces different effects. In COFDM this is typically the picture freezing and/or breaking up into blocks. I don't know what happens when 8VSB runs out of eror correction.

Channel width of 6MHz vs 8MHz is simply a consequence of band planning in the repsective countries. It just sets a limit to the bit rate that can be carried using a given channell coding system. I'm not familiar with ATSC but in DVB several programmes will be carreid in each 8MHz channel. These sets of programmes are called multiplexes. The total number depends on how heavily each is compressed and exactly which COFDM modulation schene is chosen. In COFDM parameters such as guard band can be chosen to give higher bit rate or better ruggedness.

Proponents of 8VSB and COFDM modulation have argued the respective merits of their systems but provided you can send the bits from TX to RX without pushing the error correcton over the edge they will have no effect on the pictures. I don't know all the arguments but COFDM is inherently rugged in the presence of multipath while 8VSB needs sophisticated equalisers at the RX which weren't available when it was launched. I think COFDM makes greater demands on TX linearity. The COFDM decoder is more complex as it involves large FFTs. Moore's Law soon dealt with that problem. When you factor in the equalisers needed by 8VSB that probably evens up the complexity. 8VSB is more resistant to doppler effcts if the TX or RX is moving. Not usually a problem for domestic TVs:D

What is almost certain, but possibly not too important for terrestrial TV, is that COFDM is the most efficient modulation scheme for getting the highest bit rate over a given imperfect channel. It's also very flexible since parameters such as guard band, amount of error correction, bits per symbol and number of carriers can be easily varied without changing the TX or RX. This makes it ideal for ADSL.

Well I'm thinking now in terms of HD quality (assuming no multiplexing, which they love to do) in majority of COFDM countries with 7 or 8 MHz channels. And comparing DVB-T vs 6mhz ATSC in terms of ratio of assigned resolution of Y/C - and if it still reflects the old theory that "Chroma res doesn't matter that much" - whereas we see picture simulations of progressively higher C res and, what do you know, it does matter!

So, it seems to turn out Y/C quality is more a function of sampling formats than given availability of luxurious broadcast bandwidth (DVB-T 8mhz channel)? - was curious about this. And some mastering formats have Y=C!!

The upshot of this being that the philosophy of desired chroma res has evolved from as low as one-fifth luminance to as high as full luminance res!

Please re-read the relevant part of my last post.

Can I reiterate the point that RF channel BW is almost irrelevant in a digital world. Obviously the wider it is, the more bits per second you can carry for a given error rate. Hence for a given compression system and modulation method you can carry more programmes in a wider RF channel. If you use a more modern compression system such as MPEG4 you can carry more channels or get higher quality or any tradeoff you like between them. Likewise if you use a more efficient channel coding scheme. I'm not sure how 8VSB stacks up against COFDM but I know it's not readily feasible to have a more efficient scheme than COFDM. Again I'll re-itereate that the only purpose of channel coding is to get all the bits from the TX to RX with acceptably low error rate and in an acceptable amount of RF bandwidth.

Multiplexing is simply a means of conveniently utilising the carrying capacity of the RF channel. A single 8MHz channel (or 6MHz channel for that matter) has ample capacity to carry a number of MPEG2 compressed SD programmes or a smaller number of MPEG4 compressed HD programmes. The exact number depends on how hard you are willing to compress the video. A single programme carried in that much RF BW would be a gross waste of spectrum. I don't know if multiplexing is used with 8VSB. If in the US you are using 6MHz of RF to convey a single programme then that's gross waste of RF spectrum. Maybe you've got more of it over there than we have in Europe:D I know the real reason why multiplexing is unpopular in the US. It's a socaialist plot to force the sharing of transmitters between competing TV stations.:banana:

Chroma BW is a decision made at the start of the compression process. Since the source material will usually be 4:2:2 (for SD) or multiples thereof for HD horizontal chroma res will be half of Y res. Vertical chroma res will be the same as Y res. Which is why it's usual to reduce vertical C res to give a 4:2:0 picture at the input to the compressor. Or multiples thereof for HD.

It is possible to use full BW chroma, the SDI specs and MPEG specs have options for 4:4:4 and multiples. While this may be useful in film production it has no place in transmission.

The choice of half res chroma was made back in the early days of digital experiments. I think it was settled as 4:2:2 around 1990. Can't be bothered to dig out the papers. A lot of work was done with chroma a third of luma BW but this was considered inadequate for downsteam processing and chroma key. It's proven to be a good and practical choice though a few users may have a need for full BW chroma.

I agree with all of this except the efficiency comparison. DVB-T and ATSC are essentially equal in efficiency for the same robustness level of channel coding (but DVB-T has multiple trade-offs of efficiency vs. robustness available). DVB-T2 uses more efficient error protection coding, which will very likely be adopted for ATSC 3.0 as well.

Basic color analog signal theory:

A single sideband part of the signal produces a quadrature signal component (all frequency components shifted by 90 degrees). A synchronous demodulator will ignore this component if a single SSB signal is transmitted.
However, the chroma signal has two signals transmitted at 90 degree phase difference. Each synchronous chroma demodulator then ignores any quadrature component of its desired chroma component (e.g., R-Y), but sees the quadrature component of the other chroma component (e.g., B-Y).

This is why the original NTSC specs extended only one component (I) into a vestigial sideband region. The I demodulator sees the lower I sideband, and no Q quadrature high frequencies are present because they aren't transmitted; the Q demodulator is narrowband and therefore does not see the quadrature components due to the wideband I signal.

Transmitting wideband on both chroma axes [edit: and then cutting off part of the upper sideband] introduces quadrature distortion of higher frequency chroma, but since receivers are commonly narrowband, they do not see this distorted color detail (or any color detail!). In PAL, some quadrature distortion is tolerable because of the cancellation of phase errors, so more detail can hypothetically be squeezed out of the lower sideband of non-symmetrical chroma sidebands.

A note about analog inputs: if a composite signal with wideband chroma is fed to the demodulator directly without going through the RF and IF stages that cut off the upper chroma sidebands, wideband chroma can be demodulated without quadrature distortion. Since the chroma filters in analog sets are not strictly brick-wall, you can typically see some improvement in color detail rendition when using a composite or S-video input instead of RF.

Tall towers, that the UHF DTV transmitting antennas are mounted at the top of, tend to sway in the wind. This sway can be as much as a good fraction of a wavelength of the carrier frequency up on UHF. That, combined with some significant ghosts, can make the conditions at a receiver be constantly changing. Which adds extra fun in receiver decoder design...

I think that's only a problem for 8VSB where the equaliser has a lot of work to do. The speed at which the top of the tower moves isn't high enough to give doppler shift that would trouble any plausible COFDM signal.

Thanks for the info on relative efficiency of the systems. COFDM makes it inherently easy to trade robustness for bit rate. Even to the point where single frequency networks can be used, because co-channel interference can be rejected in the same way as multipath. It's just a matter of choosing a guardband that adequate and accepting the resultant loss of bit rate. SFNs have not been used in the UK. I don't know about elsewhere.

It's worth noting that COFDM isn't needed on satellite broadcasting systems. The channel is inherently not subject to multipath or selective fading. These are the things that are dealt with by COFDM's multiple carriers, each with low bit rate, plus guard bands. A satellite channel has very high losses due to distance, plus rain fade. These cannot be helped by COFDM. There are also rare occasions when the sun aligns with the satellite. Reception is then impossible for a short period.

Doppler performance in COFDM (DVB) is limited by inter-carrier interference between the many closely-spaced carriers. Single carrier (ATSC) Doppler performance is limited by the tracking ability of the receiver equalizer, which is greatly affected by the frequency of transmission of a reference signal. In ATSC for fixed terrestrial reception, the reference sync segment is transmitted approximately 40 times per second, too slow for mobile reception. The mobile adaptation of ATSC transmits a reference approximately 800 times per second during the mobile portion of the data. COFDM achieves mobile performance by using modes with fewer, more widely spaced carriers, and through the use of reference "pilot" carriers that are inserted with the necessary density in time and frequency.

Various notes
 

Just had the leisure to check out this thread, and perhaps some collected notes could be of interest also months later:



Another one, I don't know where it originated: "Pay for Additional Luxury".

In 1977 a vision mixer had been introduced that avoided the separate chroma path with a process called Amplitude Modulated Chrominance, using an internal 5.75 MHz carrier. This was an invention of – Bosch. Seems that they at Thomson-CSF were not too happy about the best SECAM vision mixer (and other good SECAM gear as well) being Made in Germany.

But in practice more and more PAL gear came into use also at SECAM stations. Inavoidable result was at least a final PAL-SECAM conversion, and also cascades of SECAM-PAL-SECAM or even more steps were not uncommon. It is my impression that this did much more harm to the picture quality than the specific weaknesses of the SECAM system (which appear to be overemphasized thanks to clever PAL marketing, just as it is the case with NTSC).

I was not aware of this aspect of PAL patents so far. Makes me wonder how Comecon manufacturers like Staßfurt and Tesla (these two definitely made TV sets with PAL decoders) handled it.



And thus even after going to 625 lines being incompatible to the rest of the world.

"SECAM-capable" TV sets were common in West Germany, but I understand that this was just good for East German TV (and French forces TV in Berlin) while only real, expensive multinorm sets (usually also being capable of NTSC-M, put on air in Germany by AFN) could receive the crazy French "L" system.

This led to a rather widespread misbelief that "French SECAM" is different from "East Bloc SECAM". Of course it was the same SECAM III B, and I know a TV engineer who liked to provide evidence of this to surprised layman by tuning into an analogue satellite signal from France and hooking an old Staßfurt set to the modulator output of the receiver.



Reminds me of a behaviour of German (West as well as East) TV sets with decoders for both PAL and SECAM: At times the PAL decoder opened also on a SECAM signal, resulting in a rainbow picture. A screen shot of this phenomenon produced a rumour of a PAL test being done with the Inselsberg transmitter. Really just a poor rumour, because there was nothing to test here at all: The transmitter would have simply swallowed the PAL burst.



I know that I'm not the only one who now, when occasionally seing an old CRT TV (not 100 Hz technology), is wondering how we could have beared this flicker at all.

I would say no, they did not.



I.e. what is being transmit in Brazil. That's something I'm wondering about for a long time. And the same goes for the approach of Paraguay and Uruguay to modulate 625/50 video as if it were 525/60, i.e. with 4.2 MHz bandwith.

When I visited the UK and Ireland in 2000, that was what I noticed right away-the flicker on 50 Hz CRT sets. It was very strong to me, as I was only used to 60 Hz CRT displays here in the USA.

I would assume that they just ignored the patents, as was common in the Eastern Bloc. There wasn't much the west could do apart from ban imports of such goods.

Romania was the only country in the Soviet Bloc that dind't use S.E.C.A.M. The reason where politicall too! :smoke: The tv sets for Romania had decoders for both P.A.L. and S.E.A.C.A.M., 'cause all countries sorrounding Romania (except former Yugoslavia) used S.E.C.A.M. Oh, and Romania and former Yugoslavia where the only countries in Eastern-Europe that subtitled the movies (nowdays, some movies broadcasted on the Bulgarian televisions are subtitled and in Hungary from time to time movies broadcasted on tv are subtitled).

As to efficient use of spectrum, COFDM and QAM are identical, **IF**
COFDM uses no guard interval, in which case multipath removal has
to be done using the same methods as ATSC. ATSC is less efficient by a
bit because of the useless lower sideband (using the same coding
for COFDM and QAM as NTSC, of course, which can be done using plain
4-VSB for NTSC and 16QAM for the others including the COFDM carriers.)

Remember reading somewhere that the Sony idea of repeating a dropped line of chroma with a delay line wouldn't work very well in theory, but in practice it worked brilliantly, I remember how good & bright the pictures were, I was looking for the reduced vertical definition but couldn't see it. Some clever people at Sony me thinks...

All colour TV systems have reduced horizontal resolution for the chroma signals. Legacy analogue PAL/NTSC/SECAM, SD-SDI, HD-SDI and 4K. Some digital transmission methods, sometimes known as 4:2:0 as against the usual 4:2:2, reduce vertical resolution likewise. All of this takes advantage of the fact that the eye cannot resolve fine detail in colour the way it can in monochrome.

If the H colour resolution is already halved (even more reduction in analogue) then halving vertical resolution really doesn't matter.

Incidentally, a standard PAL-D decoder moves the chroma half a line down the screen compared to the luma. Again this doesn't show. It matters if you're recovering old PAL material where you would normally be using much better decoders that don't have this effect.

With Pierre Trudeau citing the need for SECAM towards allegiance with France and its two islands St. Pierre and Miquelon. He'd also want to ensure that Canadians wouldn't have full access to US programming in a way not unlike East Germany and West Berlin.