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lots of questions

affster
04-18-2006, 01:17 PM
hi there

sorry but i have a few questions i would like answered if possible...

with sd crt's i notice that alot of films and programs that aren't widescreen have black lines above and below the picture, why is this. some of them have no lines and the picture consumes the entire screen.

also with widescreen showings why are there black lines missing from the top and the bottom of the screen. why is this, i even have a widescreen crt sd and they still appear.

one other thing, i know hd programs are displayed in 720p and 1080i, slow programs work better with one of them and the other for fast things like football. what is the point in this when in the end the picture is going to get displayed in the resolution of the tv itself.

one last question, with older programs and films even though they take the entire screen up, you can see that the quality isn't very good, is the reason they appear bad quality because the camera don't capture the colours very well or is it somthing else. also when programs get rescaled to fit the screen what actually happens?

thanx

please try and help with these questions.

alex
affster

rbinck
04-18-2006, 01:41 PM
Check out these:
HDTV Pictures (http://www.highdefinitionblog.com/?page_id=92)
Bars, Bars and More Bars (http://www.highdefinitionblog.com/?page_id=6)

They should give you your answers... and maybe more.

affster
04-18-2006, 03:11 PM
hi thanx
that was all very interisting, but i am trying to figure out......

take a square tele and you will find that everything has a bar at the top and a bar at the bottom cut off.

i think i read that scientists found that staring at a square for to long makes you sleepy so they cut a bit of the screen off.... can this be true ?

with a widescreen tv alot does have the same as square tv ( bars top and bottom ) however some have a complete picture.

i would like to know if this sleepy square thing can really be true .... please help me figure this out. thanx

alex
affster

maicaw
04-18-2006, 03:24 PM
i think i read that scientists found that staring at a square for to long makes you sleepy so they cut a bit of the screen off.... can this be true ?...i would like to know if this sleepy square thing can really be true .... please help me figure this out. thanx where'd you find that info - google shot 92 blanks on {TV "sleepy square"} http://www.google.com/search?hl=en&lr=&rls=GGLG%2CGGLG%3A2005-45%2CGGLG%3Aen&q=TV+%22sleepy+square%22+&btnG=Search

BobY
04-18-2006, 09:55 PM
Given that you're in England, I wonder if some of what you are seeing are television shows shot in NTSC (525 line) converted to PAL (625 line) with the extra lines as black filler. You might see European-origin shows without black lines and US-origin shows with black lines :confused:

BrianO
04-18-2006, 11:17 PM
hi there

with sd crt's i notice that alot of films and programs that aren't widescreen have black lines above and below the picture, why is this. some of them have no lines and the picture consumes the entire screen.


If you are watching a UK analogue channel like BBC1 or ITV1 there will be many programs shown with a 14:9 aspect ratio rather than the standard 4:3 (12:9) aspect ratio. Such programs will be letterboxed (have black bars above and below the picture). These are programs that have been filmed or taped in 16:9 widescreen but are usually only shown in full widescreen on the new digital channels; on old analogue channels they are usually broadcast with the "in between" aspect ratio. The programs that fill the entire screen on analogue channels nowadays are usually those shot in the traditional 4:3 format. The 14:9 ratio is the result of a 1998 decision between the advertisers, program producers and the broadcasters in the UK regarding how to broadcast widescreen TV programming.

Try watching "Doctor Who" on Saturday on BBC1 (analogue) and then watch the rerun on BBC3 (digital). On the latter channel it will be shown in full widescreen. Just be sure that the digital set you watch BBC3 on has not been switched into 14:9 mode, a feature found on many of the newer 4:3 digital sets sold in the UK.

"Coronation Street" is another example. Both these programs are shown in full widescreen on CBC in Canada.

1080PsF
04-18-2006, 11:18 PM
Given that you're in England, I wonder if some of what you are seeing are television shows shot in NTSC (525 line) converted to PAL (625 line) with the extra lines as black filler. You might see European-origin shows without black lines and US-origin shows with black lines :confused:When converting a program to PAL from NTSC it doesnít cause letterboxing it just re-samples the 485 (525 NTSC) lines to 575 (625 PAL) lines. If there are black lines at the top and bottom (letterbox) of your raster then the aspect ratio that your watching is not a 4:3 1.33 full frame signal it must be 1.85, 2.35, or some other aspect ratio.
take a square tele and you will find that everything has a bar at the top and a bar at the bottom cut off.BTW the TV is not square itís a slight rectangle.also when programs get rescaled to fit the screen what actually happens?The signal that is sent to your TV has a set amount of pixels and each pixel has a value so let say that a 1080 signal is coming into your TV and you have a 1080 TV nothing happens because the picture will be displayed pixel for pixel, But if your signal is 720 and you have a 1080 monitor the pixels donít line-up so they have to be re-sampled. In a 720 signal each line has 1280 pixels and in a 1080 signal each line has 1920 pixels so a 720 signal needs 50% more pixels per line. So the easiest way to do that would be to take two pixels and average them together and that would be the level for the new pixel e.g. in the 720 signal, pixel number one has a value of 650mV and pixel number two has a value of 670mV so the average would be 660mV and that would be the value of the new pixel, so that would make the 1080 signal have pixel number one be 650mV pixel number two 660mV and pixel number three 670mV and that would be repeated across the horizontal line and then done vertically down the raster.

affster
04-19-2006, 02:52 AM
If you are watching a UK analogue channel like BBC1 or ITV1 there will be many programs shown with a 14:9 aspect ratio rather than the standard 4:3 (12:9) aspect ratio. Such programs will be letterboxed (have black bars above and below the picture). These are programs that have been filmed or taped in 16:9 widescreen but are usually only shown in full widescreen on the new digital channels; on old analogue channels they are usually broadcast with the "in between" aspect ratio. The programs that fill the entire screen on analogue channels nowadays are usually those shot in the traditional 4:3 format. The 14:9 ratio is the result of a 1998 decision between the advertisers, program producers and the broadcasters in the UK regarding how to broadcast widescreen TV programming.

Try watching "Doctor Who" on Saturday on BBC1 (analogue) and then watch the rerun on BBC3 (digital). On the latter channel it will be shown in full widescreen. Just be sure that the digital set you watch BBC3 on has not been switched into 14:9 mode, a feature found on many of the newer 4:3 digital sets sold in the UK.

"Coronation Street" is another example. Both these programs are shown in full widescreen on CBC in Canada.


hi
just to let you know i have a widescreen tv, english toshiba. when you say they are filmed in widescreen and broadcast in full widescreen do you meen fullscreen, without the wide in the middle of the word.

while writing this i have been watching an english program and there are small black bars at the top and bottom of the screen

i am still not 100% sure of why this is happening :S

thanx
alex
affster

BobY
04-19-2006, 09:24 AM
1080PsF-

Thanks for the info. I was actually referring to analog (or analogue :) ) NTSC/PAL. How do/did they convert between NTSC and PAL in the analog domain?

BrianO's response seems more like the answer to what Affster is seeing.

Affster-

I also have a Toshiba HD CRT. The "Full Screen" mode is the mode which displays the picture as intended, without zooming or stretching (unless the signal is anamorphic and is supposed to be stretched). If you want to see what the network intended you to see, set the display to "Full Screen". I suspect that what BrianO meant by "full widescreen" is that those stations are showing the true 16:9 aspect ratio the program was filmed in and not cropped to the 14:9 mode that is between 16:9 and 4:3 in your country (sort of a partial widescreen). We don't have that in this country, although films come in several aspect ratios and may appear with banding even on a widescreen display.

1080PsF
04-19-2006, 11:29 AM
BobY
All converters are digital based so if I send in an analog signal the first thing it does is convert to digital then it does its magic and then spits out analog and digital.

Itís funny our HD videotape machines have a selection on them for 13:9 and 14:9 output but of coarse here in the states we donít have any use for these settings. So that would make the 13:9 a 1.44:1 aspect ratio and the 14:9 a 1.56:1 aspect ratio and just like BrianO said that would cause the letterboxing to happen.

affster
04-19-2006, 12:30 PM
1080PsF-

Thanks for the info. I was actually referring to analog (or analogue :) ) NTSC/PAL. How do/did they convert between NTSC and PAL in the analog domain?

BrianO's response seems more like the answer to what Affster is seeing.

Affster-

I also have a Toshiba HD CRT. The "Full Screen" mode is the mode which displays the picture as intended, without zooming or stretching (unless the signal is anamorphic and is supposed to be stretched). If you want to see what the network intended you to see, set the display to "Full Screen". I suspect that what BrianO meant by "full widescreen" is that those stations are showing the true 16:9 aspect ratio the program was filmed in and not cropped to the 14:9 mode that is between 16:9 and 4:3 in your country (sort of a partial widescreen). We don't have that in this country, although films come in several aspect ratios and may appear with banding even on a widescreen display.


my tv is SD we don't have hd crts in england.

but what is up with some programs filling the whole screen and some filling most of it even though they are both meant to be 4:3 ? i would have thought they would all be the same seeing as they are not widescreen

ja2935
04-19-2006, 04:25 PM
1080PsF-

I also have a Toshiba HD CRT. The "Full Screen" mode is the mode which displays the picture as intended, without zooming or stretching (unless the signal is anamorphic and is supposed to be stretched). If you want to see what the network intended you to see, set the display to "Full Screen". I suspect that what BrianO meant by "full widescreen" is that those stations are showing the true 16:9 aspect ratio the program was filmed in and not cropped to the 14:9 mode that is between 16:9 and 4:3 in your country (sort of a partial widescreen). We don't have that in this country, although films come in several aspect ratios and may appear with banding even on a widescreen display.
My 16:9 Toshiba uses different picture terminology:-
Natural = shows the picture as broadcast, ie, SD 4:3 has bars at the side and the picture is undistorted (if the material has a different ratio there may be bars at the top and bottom as well) and widescreen HD defaults to this setting.
Full = uniform horizontal stretch for anamorphic DVDs - this is unfortunately the setting that many 16:9 TVs in public places are set to to watch SD 4:3 (CNN, music videos, etc) and puts many people off buying a widescreen! This is the 'short and fat' look!

maicaw
04-19-2006, 04:32 PM
my tv is SD we don't have hd crts in england.
but what is up with some programs filling the whole screen and some filling most of it even though they are both meant to be 4:3 ? i would have thought they would all be the same seeing as they are not widescreenok - how about this http://www.tvtechnology.com/features/Tech-Corner/f-rh-aspect-ratio.shtml The 14:9 aspect ratio, a compromise that produces "equal pain" when boxed in 4:3 or 16:9, is a development of the BBC that has not found favor here. The practice of pushing letterboxed pictures to the top of the screen is not done in the United States eitherand http://www.hvs.co.uk/aspectratioconv.html ...14:9 This is a halfway house adoptd by some broadcasters. The picture looks similar to 16:9 Letterbox but the black bars are not so wide. A small amount of picture information is lost at the sides. A lot of BBC programmes are broadcast in this way.. .

BrianO
04-19-2006, 10:20 PM
hi
when you say they are filmed in widescreen and broadcast in full widescreen do you meen fullscreen, without the wide in the middle of the word.


No. When I say broadcast in full widescreen I mean broadcast in 16:9, as opposed to the semi-widescreen (14:9) broadcast mode that is used on the UK analogue channels to broadcast 16:9 programming. In analogue UK broadcasting, Fullscreen still means 4:3.

BrianO
04-19-2006, 10:35 PM
what is up with some programs filling the whole screen and some filling most of it even though they are both meant to be 4:3 ? i would have thought they would all be the same seeing as they are not widescreen

You have missed the point. Some programs are still broadcast in 4:3 because they are filmed in 4:3. These are the ones that fill the entire height of the screen. Other programs are filmed in 16:9 but are broadcast as 14:9 on the analogue channels. These will not fill the entire height of the screen because they are wider than 4:3.

I mentioned "Doctor Who" because it is filmed in 16:9 and is broadcast on BBC1 (analogue) in 14:9 and BBC3 (digital) in 16:9. This gives you a chance to compare.

BobY
04-20-2006, 11:33 AM
Ja2935-

I don't know what I was thinking. I guess it's been so long since I changed my screen mode that I forgot how it worked :o. My Toshiba is the same as yours--"Natural" shows you the signal as intended and "Full" is a linear horizontal-only stretch for anamorphic.

Affster-

So your set is a widescreen CRT digital TV, but not HD? Are the 16:9 broadcasts in England HD or SD? If they're HD, does your set downscale them to SD? Just curious...

1080PsF-

But how did they convert NTSC programs for transmission as PAL in the decades before digital conversion? Were the extra lines blank (black)?

1080PsF
04-20-2006, 12:56 PM
1080PsF-

But how did they convert NTSC programs for transmission as PAL in the decades before digital conversion? Were the extra lines blank (black)?Digital has been around for a long time. Standard converters have been digital since I've been using them and I've been working in post-production for 20 years. The first converter I worked with was an ACE standards converter and it was really big, it fit in two six-foot high racks. Even back then it didnít letterbox the output it just re-sized the picture to gain those hundred lines (going NTSC to PAL). As time went on the converters got better and smaller now days a SD standards converter is only one rack unit high.

The first all digital videotape machine came out in 1987 it was an 8-bit component recorder know as a D-1 it was made by Sony and they are still is use today. Before that was a videotape machine that was analog video and three tracks of analog audio but also had two digital tracks of audio I forget when they came out.

BobY
04-20-2006, 01:10 PM
OK, it's highly unlikely that anything Affster is seeing today has to do with NTSC-to-PAL conversion. But just out of curiosity what did they do in the 50's, 60's and 70's to convert NTSC to PAL?

1080PsF
04-20-2006, 02:05 PM
OK, it's highly unlikely that anything Affster is seeing today has to do with NTSC-to-PAL conversion. But just out of curiosity what did they do in the 50's, 60's and 70's to convert NTSC to PAL?
To tell you the truth I don't know, but PAL was first introduced in 1967. So that takes care of the 50's and most of the 60's. My best guess would be that it was still digital because 1" machines used digital TBC's and they came out in the 70's.

BobY
04-24-2006, 01:27 PM
I thought PAL was introduced in the early 60's...

In any event, I doubt anybody was doing anything with digital conversion in the 60's. The first semiconductor memories weren't introduced until the 70's--memory back then consisted of flip-flops while D/A and A/D converters were far too slow to operate at video frequencies.

Still curious :D ...

maicaw
04-24-2006, 02:29 PM
Still curious :D ...check this page http://www.videointerchange.com/pal_secam_conversions.htm#Pal Conversion Quality Considerations
Scroll up the page for some really interesting tech history about the color subcarrier and 29.97 frame rate choices - strictly for NTSC broadcast reasons- not critical for tape, laserdisk, PAL etc.

Porcupine
04-24-2006, 02:57 PM
Aw, what happened to Captain Kirk? :)

I don't recognize the person in your new avatar, who is he?

maicaw
04-24-2006, 03:18 PM
Aw, what happened to Captain Kirk? :)
I don't recognize the person in your new avatar, who is he?Denny Crane's idol Phineas Taylor who? (http://en.wikipedia.org/wiki/P.T._Barnum) - see also Anti-heroes. (http://en.wikipedia.org/wiki/Denny_Crane)Crane's expertise, skill in media manipulation and reputation ... His aggressive personality, massive ego, ...eagerness for the limelight etc. etc..

BrianO
04-24-2006, 04:59 PM
I thought PAL was introduced in the early 60's...



In the UK, BBC2 made its debut in early 1964 using PAL, and they were not the first to use PAL. BBC1 and ITV continued to use the old British 405 scan-line system (4.5 MHz bandwidth VHF channels) until 1982, but began simulcasting in PAL around 1969.

As for the OP's question, cross-conversion from one format to another is NOT the cause. In the 1950's there were a number of broadcast systems with different numbers of scan lines in use in Europe, but that did not stop the establishment of Eurovision which allowed programs to shown across Europe. The real-time conversion from one format to another was handled by the individual broadcasters and never involved letter-boxing or pillar boxing because 4:3 was the universal standard aspect ratio. The launch of Telstar in 1962 allowed transatlantic TV broadcasting which involved cross-conversion to and from systems that had different frame-rates in addition to differing number of scan-lines. Once again, no change in aspect ratio was involved. This is decades-old technology.

BrianO
04-24-2006, 05:03 PM
Aw, what happened to Captain Kirk? :)

I don't recognize the person in your new avatar, who is he?

Pay attention! His old avatar was not Captain Kirk; it was Denny Crane, a role for which Bill Shatner has won 2 successive best supporting actor emmies on 2 different TV programs.

BobY
04-24-2006, 07:56 PM
Yeah, the idea that it might have been the result of NTSC-to-PAL conversion was a wild guess on my part.

But what I'm curious about is how did they do the conversions from one format to the other when the scan rates were different and the number of scan lines were different. I'm not disputing that it was done, I'm just curious how they did it--I just don't believe it was done digitally back then.

Did they put it up on a display, then scan the actual screen image at the new rate?

ja2935
04-25-2006, 05:15 AM
I can't imagine it is a difficult process. My $100 DVD player happily plays PAL discs and converts to NTSC with no noticeable difference with its built-in converter.

BobY
04-25-2006, 09:31 AM
Sure it's easy today with digital conversion. I'm talking about the 60's...

rbinck
04-25-2006, 10:36 AM
Some of the better, and most expensive, converters used analog computers. Back in the 60s there was a lot of research and development of analog computers and calculators used for a number of other areas as well. Eventually the digital world surpassed the analog world in power and size which made the analog computers a thing of the past. An analog interpolator was the basis for the early line doublers, before digital.

BobY
04-25-2006, 10:57 AM
I actually played with an analog computer very early in my schooling--integrators, adders, multipliers--all separate circuits with input jacks and output jacks! Most people don't realize that analog music synthesizers (ala Moog Modular) were essentially analog computers.

But is that *really* how they converted video formats back in the 50's and 60's? Do you have any equipment links you can give me?-- I'm really fascinated by this.

rbinck
04-25-2006, 02:41 PM
I looked a bit and it seems you will probably need to go to your local library to do that sort of research or spend a lot of time in google. I did find a guy who claims to be using an Emerson PAL to NTSC converter that throws away some of the lines and requires you have a TV with an adjustable vertical hold to make up for the different sync. Good luck on your search.

Porcupine
04-25-2006, 02:55 PM
Analog computers? Can such things actually exist? I cannot fathom how they might work. Hmmm. :eek:

Something interesting for me to think about.

maicaw
04-25-2006, 03:00 PM
Analog computers? Can such things actually exist?
VINTAGE Heathkit Educational Analog Computer EC -1 (http://cgi.ebay.com/VINTAGE-Heathkit-Educational-Analog-Computer-EC-1_W0QQitemZ8799647597QQcategoryZ1247QQssPageNameZW DVWQQrdZ1QQcmdZViewItem)
later (cheaper) ones use IC Op-AMPs - easy to build one with an old heathkit 12v/5v breadboard and $50 worth of RS parts - BTDT in a College Physics lab in the 60s.
The "Neural Network" software (such as Brain Maker - California Scientific / BrainMaker Neural Network Software http://www.calsci.com/ )that runs under windows essentially uses your PC to construct a virtual analog computer. -

BobY
04-25-2006, 06:02 PM
Analog computers-the "stone knives and bearskins" approach (yes, I'm dating myself--if you don't understand the reference, ask Denny Crane :) )

Before there were digital solutions, if you wanted to solve an equation with, say, a complex integral, you put a voltage into the inputs of an analog integrator (aka a buffered capacitor) and measured the output voltage on an *analog* meter.

Now a digital emulation of an analog computer is an amusing idea.

maicaw
04-25-2006, 08:13 PM
Now a digital emulation of an analog computer is an amusing idea.Not amusing -but highly useful, functional, valuable - if you have the intellectual ability to formulate the time-series (analog) data and remove the insignificant parameters - much like MPEG does with raw HDTV- READ through the "applications" on THE LINKS - hardly "stone age" stuff - the pros have always understood that it's an analog world -digital is just the technological "emulation" (iterative model) of the real world.
Your example was a simple shunt capacitor circuit element - about as related to an analog computer as a flip-flop is to a Pentium Microprocessor - Professional virtual analog computers are performing sophisticated pattern analysis many orders of magnitude beyond your apparently limited experience -
Digital TV uses analog RGB camera signals -manipulated by digital hardware to generate analog component video outputs to your display.
Stone age my ass
Denny Crane, Denny Crane, Denny Crane!

BobY
04-25-2006, 08:36 PM
Gee Whiz, I wasn't referring to your links, I was referring to *my* experience with analog computers in school (and they *were* stone knives and bear skins compared to a digital computer).

There are those who would argue that it is, in fact, a "digital" world when you get down to the quantum physics and that there really is no such thing as an analog signal, just an approximation of one with ultra-high-resolution quanta.

Let's see, that would make a digital emulation of an analog computer a digital approximation of an analog approximation of a digital approximation of an analog approximation of reality...

Hey I'm kidding, this is too deep for me :)

BobY
04-25-2006, 08:55 PM
Please don't think I'm a digit-o-phile. I've worked with analog and digital electronics for over 25 years. So much digital stuff (including HD) is shot through with hooey.

My personal favorite audio amplifer uses vacuum tubes and I can absolutely hear the difference between a Class A triode and any transistor design (though some FETs come close).