BTW, sailor, I’m still curious about what you meant by saying that 525 lines is a ratio of some sort, not a line count. Are you perhaps thinking of the Kell Factor?
>> paper explaining screen size and overscan
Yes, I know what is straw man is, thank you very much. I had already said “Lines which carry data and are not displayed are actual lines as they could be displayed” which is the definition of overscan. Not a single one of your links contradicts what I said but thank you for posting them anyway.
I will remind you I was talking about the retrace and on that we’ll just have to agree to disagree. The way I see it, after completing a field the electron beam returns from one corner of the screen to the other corner without scanning horizontally and therefore I consider there are no lines. The fact that this retrace takes the time it would take to scan seven lines does not mean to me that there are in fact seven lines there. The beam does not scan lines horizontally across the screen during the retrace.
I’m with sailor. While we’re discussing picture quality, it’s not productive to jump in and proclaim that “all US TV’s have 525 of resolution”. No TV has 525 lines of resolution that it can use for displaying a picture, and that’s what the original poster was talking about. And discounted from that 525 is a whole lot more than the 7 lines which are required for the vertical retrace interval: you’ve also got some number of lines which contain actual data, such as closed-captioning text (which is on line 21, so you lose at least 21 lines to pure non-picture-related data), plus the overscanned part of the picture.
And for what it’s worth, I don’t think there’s any law about TV’s having to conform to NTSC – there’s a law about what you can broadcast, but it’s quite possible to buy PAL/SECAM TV’s in the US.
As I said above, I believe a field has 241 lines so, if I am not mistaken, 482 would be the max a TV could display even if there was no overscan.
galt, the line “all TVs, by law, are built to display a signal with 525 lines” is, obviously, nonsense but I am not sure if the FCC would deny a broadcast permit solely on the grounds that you want to broadcast on a different format. I can’t think of a good reason why you would want to do it but if you had a reason would they object?
I will add to your observation that NTSC does not equal 525 lines / 60 frames and that PAL does not equal 625 lines / 50 frames. NTSC and PAL are standards for carrying the color information and NTSC and PAL exist in other frequencies. Specifically, there exists 625/50 NTSC and 525/60 PAL. Not common but they exist, as well as other frequencies. It is common to say NTSC to mean 525/60 and PAL to mean 625/50 just because those are the most common standards but, again, PAL and NTSC are standards for coding the color information and have nothing to do with scan frequency.
>> BTW, sailor, I’m still curious about what you meant by saying that 525 lines is a ratio of some sort, not a line count
squeegee, I think I explained it quite clearly when I said
I do not know how I can clarify that except to say that the vertical scanning is at a rate of 59.9x frames / sec (the exact number is not 60) which is a scanning rate of one frame every 16680 microseconds. The rate at which the lines are scanned is 1/525 of that or 31.77 microseconds. So, if you take a “line” as a unit of time, then a frame has 525 lines.
If I say “the close captioning information is contained in line X” I think we understand “line x” defines an amount of time between two horizontal sync pulses and it is no reference to a line which would scan on the picture.
Wrong in most cases. If your computer monitor uses the standard HD15 VGA connector, then it’s analog. If it’s DVI (some newer LCD screens use this) or a laptop, then it’s digital. The digital-analog conversion is done on the video card. That’s where the pixels exist. For CRT monitors there is not usually a 1-1 mapping of displayable dots on the screen to digital pixels on the video card (for LCDs there is, otherwise the picture looks bad). This is why CRT dot pitch is important; if you have a monitor that has the bandwidth capable of displaying a hi-res image, but has a large dot pitch, you still won’t see all the pixels.
Sailor, I think we’re saying much the same thing. My exact point was, you can’t define the resolution of a TV (and my points were confined to NTSC, which I clearly said) without stating more about what signal the equipment is built to display.
Which is exactly what I said. And then I elaborated on the blanking area of the signal and overscan techniques that most TVs use. What’s the problem?
The NTSC signal has 525 lines (yes, defined as a time interval. Whatever). All Televisions sold for the US market are built to display that signal. 483 of those lines are ‘active’. What’s wrong with that statement?
I disagree. I shall find a cite if you like.
Cite, please.
Nonsense. The scan frequency is mandated by the FCC in the US. If everyone broadcast on different scan frequencies, televisions would all be incompatible with each other, which clearly isn’t true, so this is clearly a standard. Cite please.
The exact number is 59.94005994005994005994005994006 hz. So what?
Sailor, as I said, we’re saying much the same thing. I’m talking about a signal which is 525 lines/intervals/potatos/whatever, and I said that 483 are active, and therefore contain picture information. What’s the problem?
I agree, and I corrected that statement later in the thread. You must have missed it.
A bit of practical side by side comparison.
I just switched from a 55" big screen NTSC TV to a 65" HD set.
It is extremely clear that conventional TV’s lack either the dot pitch or beam focus to display all the information output from a DVD.
The exact same DVD looks enormously better on an HD set. There is very noticably more detail available.
Conventional NTSC may be scanning all or most of the DVD’s 480 lines, but it isn’t doing a good job of it. The sharp detail need to read small text does not get though on a regular TV.
I am sure this is exactly the problem when sending VGA to the TV. The data may be getting to the TV fine, but the TV simply doesn’t have the precision to display it adequately.
Even while an NTSC TV may theoretically display 483 lines( even less with overscan), the focus of each line is poor enough, that usable resolution is probably about half that.
btw, an HD set will display 640x480 VGA as crisply as a good monitor. HD sets also use the RGB color space instead of the luminance, chromanance crap. A sunset finally is the color of a sunset… it is spooky different at first.
Forgot the tie in to the OP.
The whitebook VCD format of 352 x 240 is probably very close to the maximum usable detail a standard TV can display.
Also, for those who don’t remember when TV’s were commonly used as monitors (Tandy Color Computer, Commodore Vic-20 or C64), the graphics cards in those were in the neighborhood of 350x240. The video out was simply line doubled and framed. They knew it was a waste of time trying to send more data than that, to the TV. Text was just barely readable with 350x240 as the base resolution.
squeegee, I am waiting for a cite on your assertion that “all TVs, by law, are built to display a signal with 525 lines”. A valid cite being a cite of a US statute not a lot of hand waving and links to standards which are not laws.
>> The NTSC signal has 525 lines (yes, defined as a time interval. Whatever).
Yeah, whatever. You seem to have a hard time admitting I was right. Whatever.
>> All Televisions sold for the US market are built to display that signal.
Nope. I can take you to a dozen stores in the DC area where you can buy appliances for other standards. I, myself, have a multisystem TV and VCR. I hope this is not illegal. At any rate, your assertion is absolutely, 100% irrelevant. even if it were true that “All Televisions sold for the US market are built to display that signal” what does that have to do with whether the signat has more or fewer actual lines?
I said “but I am not sure if the FCC would deny a broadcast permit solely on the grounds that you want to broadcast on a different format”
You said: “I disagree. I shall find a cite if you like.”
Yes, I "would* like to see it because, while I am not absolutely certain it does not exist, I find it doubtful. So, yes, I will put it on the list of cites I am waiting for, together with the “law” making the 525 lines the law of the land.
I said “NTSC and PAL exist in other frequencies. Specifically, there exists 625/50 NTSC and 525/60 PAL. Not common but they exist, as well as other frequencies.”
squeegee: Cite, please.
No problem. But before I give you the cite I would point out that if you had just searched for “TV standards” you would have found a gazillion pages giving you all the information. It’s not like TV standards are some obscure information. And now some links. Check out first this page and you can see TV standards fall into several groups. Frame scan frequency, lines per frame, etc are designated by letters and are independent of color schemes which have names (NTSC, PAL, SECAM, etc) and then you have even more standards for sound etc. NTSC and PAL are compatible with several frame and line frequencies as you can see there. Specifically there are many different implementations of PAL and NTSC around the world. For the most part 50Hz countries chose PAL while 60 HZ countries chose NTSC but not always and even within the same frequencies there are different implementations as you can easily find out if you look at any chart of TV standards around the world. BTW, I wil have you know the USA does not equal the world. There are aother places out there that have TV. Just take my word for it.
I said: “It is common to say NTSC to mean 525/60 and PAL to mean 625/50 just because those are the most common standards but, again, PAL and NTSC are standards for coding the color information and have nothing to do with scan frequency”
squeegee: “Nonsense. The scan frequency is mandated by the FCC in the US. If everyone broadcast on different scan frequencies, televisions would all be incompatible with each other, which clearly isn’t true, so this is clearly a standard. Cite please.”
Look, I am really getting tired of this nonsense. Stop setting up straw men. There is no way in the world that what you say follows from what I say. You are saying I said TV stations in the US use different standards. Can you explain where you get that from my statement?
I stand by my statement
Note I do not mention the US nor do I imply anything beyond what I actually say there which is that NTSC and PAL are color standards independent of frequency. besides the link I gave above you can check http://hotel04.ausys.se/pausch/tv/tv.html . It is a long page (you might want to read it and learn something). Look for the NTSC standard and read where it says “Bandwith of Q is reduced (to 0.5 MHz (USA/525) or 0.6 MHz (CCIR/625))” so, it seems there is an NTSC standard for 625 lines. Also where it says “A few countries like Brazil use a 525-line variety of PAL called PAL-M” I have not read the whole page but it clearly demonstrates my assertion is correct.
>> The exact number is 59.94005994005994005994005994006 hz. So what?
So I was right? You seem to have a problem with others being right?
>> Sailor, as I said, we’re saying much the same thing.
Wow, you fooled me there. At any rate, looking forward to those two cites, I remain yours faithfully, etc, etc.
Maybe some kind mod can fix that bold tag in my previous post?
BTW, that page I linked to has a chart which gives for the different systems Total Lines, Active lines, Vertical Resolution, Horizontal Resolution, and even things like Optimal Viewing Distance.
sailor, I will search for your cites when I have a moment.
But, where did you miss that I was discussing the US which (I said several times)?? And then you trot out Brazil to discuss 625 line scan rates. Sheesh, talk about straw men.
Oh, and you want to nitpick about a number not being 60, so I nitpicked back with the real correct number when your ‘correct’ number was incorrect. If you want to nit on dumb stuff like exact vertical scan frequencies we can do this all day. Do you have actually have a point or are you just one-upping for no particular reason?
squeegee, I have a feeling we are going to end in the pit where I can be more direct if not more convincing.
>> where did you miss that I was discussing the US
Um, no, you were most definitely not discussing the US. You were refering directly to my quote that “NTSC and PAL exist in other frequencies. Specifically, there exists 625/50 NTSC and 525/60 PAL. Not common but they exist, as well as other frequencies” Furthermore, if you had bothered to read the links I supplied, you would have seen that the USA uses a type of modulation called “M” which is the one which specifies the frame frequency while NTSC is the color standard which can be used with different frequencies as illustrated by the case of Brazil. But In the USA, in Brazil and everywhere in between, NTSC is a color-encoding standard and does not imply any specific frequency. This is true in the USA. Which was my whole, entire, freaking point. Do you undertstand that? I will repeat it: It is as true in the USA as in Argentina. Ok? Just read the freaking links. Sheesh.
>> Oh, and you want to nitpick about a number not being 60, so I nitpicked back with the real correct number when your ‘correct’ number was incorrect
No, I did not supply any wrong number. I said “59.9x frames / sec” precisely because I did not remember the exact number. But I can assure you, if I had made a mistake in something I said, I’d be willing to admit it without a problem.
>> I will search for your cites when I have a moment.
That would be nice.
I give up. You can’t even be slightly civil about geeky dumb crap like this.
Tell you what, sailor
Everything you said was totally right.
Everything I said was totally wrong.
Happy?
Don’t sprain your wrist congratulating yourself.
Oh, yeah:
And the horse you rode in on.