English NTSC TV's.

[NewVista]

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?).

[old_tv_nut]

Originally Posted by NewVista

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?).

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

[dr.ido]

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.

[NewVista]

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!

[ppppenguin]

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 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.

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.

[old_tv_nut]

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.

[dtvmcdonald]

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.)

[Telecolor 3007]

https://www.oldtechnology.net/colour4.html

[Colly0410]

Well Brazil had a PAL 525/60 system, so maybe Canada should have had a SECAM 525/60 system to keep things equal, but common sense prevailed & they chose NTSC. England tried experiments with NTSC, SECAM & PAL on both 405/50 & 625/50 in the 1950's/60's. A few experts wanted wanted to go for NTSC, but eventually they went for PAL, we could have been the only NTSC 625/50 country in the world, wonder how that would have panned out?

[colorfixer]

Originally Posted by Colly0410

Well Brazil had a PAL 525/60 system, so maybe Canada should have had a SECAM 525/60 system to keep things equal, but common sense prevailed & they chose NTSC. England tried experiments with NTSC, SECAM & PAL on both 405/50 & 625/50 in the 1950's/60's. A few experts wanted wanted to go for NTSC, but eventually they went for PAL, we could have been the only NTSC 625/50 country in the world, wonder how that would have panned out?

PAL-M was chosen to allow in part for Brazil to develop it's own domestic industrial base.

[BRC2000]

Hi All
R.C.A sold CTC11 / 15 / 16,s which had been converted by them to UK system I 625/50 4.43Mhz NTSC 240v 50Hz power in the early 1960s and some still exist.
I have ctc11 / 15/ 16 TVs the 15 and 16 are working well with good pictures.
If you go to :- https://www.vintage-radio.net/forum/...ighlight=ctc16 you can see the ctc16 coming back to life.
Keith

[jhalphen]

Hi to all,

On the topic of NTSC experimentation outside the US, Switzerland had a go at testing it also in 1957 with a modified RCA set; see the info on the ETF site :

http://www.earlytelevision.org/rca_21ct55_swiss.html

Best Regards
jhalphen
Paris/France

[Mr Hoover]

There's a lot of interesting information on that site.
Think it was somewhere in there I read about tests that were done after the relatively low earth orbit Telstar satellite was launched to check the doppler shift caused by the satellite's motion relative to the ground stations didn't vary the NTSC colour subcarrier frequency much, it ended up being 10-12 Hz from memory which was acceptable.

[DavGoodlin]

I was always amused by this depiction of British TVs in a Monty Python episode. The truck outside unloading more TV's elicited some uproarious laughter from friends and family who used to think that I was the only old TV collector. LOFL

This outrageous humor is not for everyone but if you fast forward to 11:14 you'll see alot of them.https://www.dailymotion.com/video/x6gf7qi

[Hawkwind]

MPFC also did a "Department Store" sketch. They show a directory of what is on each floor and where it says "Roof", the listing is "TV Aerials"...