Progressive Scan - I don't get it !

[VCDHunter]

As I understand on interlaced NTSC both fields are displayed at once, twice as opposed to one after another to create a frame. But what the hell happens on PAL ? Its not interlaced but I understand it has 2 "fields" - so how do these fields exist, are they similar to interlaced video ?

[FOO]

interlaced NTSC both fields are displayed at once

Not true

PAL on a TV shows 50 Fields per second -> 25 fps
NTSC on a TV shows 60 Fields per second -> 30 fps

what's the confusion about that ?

I don't know if progressive shows 2 identical frames in a row
at the field rate or not.

I have heard that movie theaters show 3 frames in a row at 72 fps

[bugster]

But what the hell happens on PAL ? Its not interlaced

Pal Tv's ARE interlaced, they just use 50 fields per second as opposed to 60 for NTSC.

[VCDHunter]

PAL on a TV shows 50 Fields per second -> 25 fps
NTSC on a TV shows 60 Fields per second -> 30 fps

what's the confusion about that ?

Well I can understand that interlaced NTSC video has alternate "lines" that make up a frame. Is PAL video the same, I mean does it have alternate lines like NTSC ? I've read that it is made up of two fields (A and B) but what does that mean ?

Thanks

EDIT: Sorry bugster didn't see you there - thanks I think that has answered my question unless FOO would like to interject with any further info Does this mean that ALL DVDs I have (PAL or NTSC) are interlaced ?

[VCDHunter]

interlaced NTSC both fields are displayed at once

Not true

A brief bit of reading yesterday led me to believe that on a progressive scan both fields are read in one pass and displayed twice to create a frame is this not the case ?

[lechtin]

In both PAL and NTSC, the screen is made up of 2 fields. The screen first scans the odd-numbered lines to make up the first field, then the even-numbered lines to make up the other field (don't ask me which is which). This makes up one frame, and the whole process is repeated 30 times per second on NTSC, and 25 times per second for PAL. These are the frames per second. The total number of fields is 60 or 50 (30 or 25 of field A and 30 or 25 of field B)

BTW, NTSC is made of 525 horizontal lines while PAL is made up of 625 lines (they are not all visible for reasons too long to get into here)

NTSC and PAL are both interlaced video. In progressive video, the screen scans the lines one at a time, from the first to the last, and this usually happens also 60 times a second, but since each line is part of each scan, the frame rate is then 60 frames per second - twice that of interlaced video (I'm in North America, I don't know of progressive scan in Europe is 50 frames per second). Therefore, progressive scan gives a much better picture. Your computer is a prime example of progressive scan (adjustable at that if you ever played with the frequency of your video card's settings).

Note: film is movie theaters is 24 frames per second and is NOT scan, either progressive or interlaced - this only applies to CRT screens which is not the case of movie projectors. They project light throught a cellulose film which is fed at 24 images per second to create the image on the screen.

[VCDHunter]

Christ - there are some smart mofos on this board. Thanks all, a sterling effort, by jove I think I've got it.

[bugster]

interlaced NTSC both fields are displayed at once

Not true

A brief bit of reading yesterday led me to believe that on a progressive scan both fields are read in one pass and displayed twice to create a frame is this not the case ?

If you have a progressive scan display, a progressive scan DVD player and a progressive DVD, then everyting is progressive.

Most commercial DVD's are interlaced. If played on a progressive capable DVD player, with a progressive display device, then I think you are correct in saying that

both fields are read in one pass and displayed

But not displayed twice as such, just displayed for twice as long as individual fields.

[iThinkYouBrokeIt]

they should encode dvds in progressive for those who have progressive scan, or watch on their computer.
i dont see why not, when they encode them in 16x9 despite how most people own 4x3 sets...

[bugster]

when they encode them in 16x9 despite how most people own 4x3 sets...

They are often encoded in 16x9 or even 'narrower' aspect ratios to preserve the movie the way it was shot and intended to be shown. Cinemas don't have 4x3 screens!

Also, your comment about how many people own 4X3 sets, I don't know about where you come from, but here in the UK (and much of Europe I believe), though 4x3 may still be in the majority in the home, most new sets sold are 16x9 and more and more material is being transmitted in 16x9. Its the way we are going. Unfortunatley, progressive scan displays are still rare.

[energy80s]

ALL television is interlaced. There's no such thing as a progressive scanned TV programme. Film is progressive by its very nature - 24 still frames a second. Although there are tricks that can be preformed on video to make it progressive, as it started out as interlaced, you are much better off keeping it interlaced right through to the display screen. As most people watch TV shows at home rather than films, the vast majority of TV sets are interlaced display only. Widesceen is a whole different issue. In the UK , I think about 33% of all TV's are now widescreen (I don't own one myself - and don't want one either!) but elsewhere its MUCH less. The next World Cup football tournament from Germany is to be in full widescreen, even though only about 6% of German homes have widescreen tellys!

[bugster]

In the UK , I think about 33% of all TV's are now widescreen (I don't own one myself - and don't want one either!)

Just curious, why would you not want a widescreen TV (assuming you were looking to replace your existing set anyway).

[iThinkYouBrokeIt]

when they encode them in 16x9 despite how most people own 4x3 sets...

They are often encoded in 16x9 or even 'narrower' aspect ratios to preserve the movie the way it was shot and intended to be shown. Cinemas don't have 4x3 screens!

Also, your comment about how many people own 4X3 sets, I don't know about where you come from, but here in the UK (and much of Europe I believe), though 4x3 may still be in the majority in the home, most new sets sold are 16x9 and more and more material is being transmitted in 16x9. Its the way we are going. Unfortunatley, progressive scan displays are still rare.

The video is always encoded in 4x3 or 16x9. Those are the standards. If a different aspect ratio is needed, letterboxing will be used. and yes i know that Cinemas don't have 4x3 screens. it is blaringly obvious to me that most are "more or less" 2.35:1
I know what widescreen is, and i hate it when films are shot in Super-35.

and here in the United States, most people own 4x3 sets and have a 2.0 sound system. some have 16x9 w/ progressive scan and 5.1/6.1 sound systems, but the majority of the people do not.
also, a lot of people seem to prefer the fullscreen format, so fullscreen dvds are being produced to meet the publics needs. most of the people i know prefer widescreen dvds, though.
I personally would rather have a 2.35:1 set, but they do not exist.

[Nelson37]

OK, there are two statements here I must strongly disagree with.

"Nearly all commercial DVD's are interlaced" - I have only done 6 to 8 or so, but I have yet to see an interlaced DVD, and it seems to be the consensus on this board that interlaced DVD's are rare.

"ALL television is interlaced" - When I cap cable movies, they are clearly TELECINED - only 2 of 5 fields are interlaced, with the other 3 showing no signs whatsoever of interlacing. I am curious as to how this is done in terms of the 60 fields per second transmission standard??

[FOO]

Your capture card is grabbing every two fields
and combining them into a frame. 40% of the time the fields are from the
same original frame and match fairly well.

They are ALL interlaced . Your capture card is receiving 60 Fields
per second . You have no way of knowing this is happening if
the 2 fields originate from 1 Film Frame and the capture combines them.

ALL TV is interlaced.

I have yet to see an interlaced DVD

How do you decide if it is or not ? I have never seen one that is not
interlaced after about 500 or so