Like farss said...

What you can do if you're in doubt is right click on the source file once its on the timeline then look under the media tab. If it shows either upper or lower field in the field order box, then its interlaced material.

Interlacing is a relic of old TV technology.

<things you maybe wondered about but didn't know why>

As most probably already know a "movie" like you see on the big screen in some theater is really just a bunch of still images (frames) that go by fast enough so that your eyes "sense" movement.

One of the main reasons this works is something called persistence of vision. That's because every image you "see" is retained in your eyes for a fraction of a second. So as Edison discovered long ago if you look at a series of images fast enough, this persistence of vision creates the illusion of motion. While Edison was surely brillant, he didn't get the ideal frame rate right. He used 16 frames a second, which some chap in Europe speeded up to 25 frames which is better. For you purists as you known movies are filmed at 24 frames a second and none the less are broadcast at 25 frames a second in Europe and at 29.997 in the states, and they don't seem to suffer because of it.

Now the "fun" part....

Your persistence of vision decreases as the image gets brighter. Sadly that can cause the image to flicker, because the past image has already faded from the eye's memory. Oops...

A simple solution for movies was to put a shutter in front of the projector.No more flicker.

For TV another method had to be found. To understand, remember all televisions paint the image on screen one line at a time left to right, top to bottom. It happens very fast. That picture your watching is actually being redrawn one line at a time time actually in a pattern that does every other line then goes back. That's interlacing. So to replace the shutter that very briefly blanks the image between every frame the image is painted on screen twice with each frame having two fields. The first pass does the odd lines (lower field), the second the even lines or the upper field.

Now there's a fly in the ointment.

With NTSC the frequenly originally was set to 60 HZ. It was changed to 59.94 to allow better seperation of the audio signal to avoid introduction of noise caused by the visual signal. Now those good in math perhaps are starting to see why we ended up with such a goofy frame rate of 29.997. Its because we in the U.S. use AC electrical current of 60 Hz, those in most of the rest of world have electrical current distributed at 50 Hz which is WHY they use 25 frames per second. The result is better, because that means you can have more lines of resolution, but that's another story.

So, interlacing is there so both fields, the lower and upper (even and odd) frames can get merged back together to form the whole picture. So the picture you see on TV is actually redrawn 60 times a second, (well roughtly) in alternating lines.

Interlace flicker in part is caused when things get out of sync or when there is rapid action or when vertically adjacent picture elements one frame to the next do not line up perfectly. You see the telltale result, the image shimmers at little or you see ghosting. Again that darn persistence issue again.

The interlace problem would go away if projectors were changed to display 29.97 frames a second, even rounding up to 30 frames per second would be better. But it isn't going to happen.

Finally interlacing can show up more on some TV's than others due to a similar problem ; persistence of the color phospers used in the TV tube. Some will retain their charge longer than others. So if interlacing is a slight problem or hardly any at all depends in part on what TV you're viewing and if or not it is properly calibrated.

Thanks for the replies.

Just to clarify a couple of points. I have created a graphic using Lightwave which has the option to output interlaced or noninterlaced into an AVI file. On reflection it would probably make sense to interlace the output file as it may reduce the render times.

Thanks


Warren.

As i understand it the original system was frame based however as CRTs were built with more brightness flicker became a problem. They could have got aroud that by painting the screen quicker but they didn't have the technology to store a frame so you had to paint it as it was recieved, that meant you hit a bandwidth limit or else for a big part of the time the bandwidth wouldn't have been used. The answer was using interlacing and pulldown. Remember also early TV transmission was totaly film based, there were no TV cameras, so called live broadcasts involved running film through a camera, down a ligt tight pipe, though a prcessing plant and into a telecine.

Remember also early TV transmission was totaly film based, there were no TV cameras, so called live broadcasts involved running film through a camera, down a ligt tight pipe, though a prcessing plant and into a telecine.

This is a new one on me, I've been in this business a LONG time and I've never heard of this. Live television was always shot with a TV camera, but it wasn't until the team at Ampex came up with a video recorder in the late 50's that one could record video to tape. Up until then, anything intended for archiving or delayed broadcast was filmed. (By the way, Ray Dolby of Dolby Noise Reduction fame was on the team at Ampex that invented the video tape recorder.)

John

What I was talking about may have been before it was a commercial system but I recall some pictures of a system that did just that. Of no real interest other than as a historical sidenote.

I guess it goes in the same place in history as the 'live' radio coverage of overseas sporting events, the action came out on tickertape and a cast and folly artists in a studio recreated the 'live' sounds.

I've noticed you went on WAY TOO LONG, mostly tooting your own horn John. It is further noted you had plenty of time to knock one of world's most horored inventors. I guess you weren't pressed for time until after you finished.

http://www.tomedison.org/invent.html

BTW, I didn't say anywhere in what I wrote that Edison invented the projector. History credits Edision with inventing the phonograph and the motion picture camera and discovering the electric light. Care to give your altered view of history on those?

Edison was granted over 1,000 patents. How many you have John?

Curious view of a hack.

Nikola Tesla once worked for Edison. Saying he and Edison didn't see eye to eye is an understatement. Kind of like you and me on some topics. The question of course is why did you find it necessary to attack Edison and carry the torch for Tesla here in this forum of all places?

Originally, I simply mentioned Edison in passing. You on the other hand go full bore, spit and vinegar, attacking Edision right and left for no reason. How "professional" of you. Not!

You're also getting as bad with your overuse of bold text in some vain effort to make a point as Zippy and his excessive use of all caps. It looks childish when you both do such things. What you say and how you say it is more forceful than using bold or caps.

I also noticed you tend to easily get bent out shape if someone doesn't agree with your point of view.

You've over reacted with me on many topics John. To a kidder like me that loves to tease its just an open invatation to nettle you all the more. I though someone as clever as you like to paint yourself would have noticed. Guess not.

>I was just trying to give Tesla the credit he deserves (as I have been for the last 30 years.) And, yes, by comparison to Tesla, Edison was a major league hack.

I don't want to step in between the two of you, but I confess that I also have the same knee jerk reaction as John Cline whenever Edison is mentioned: The truth is that as successful as Edison was in some areas, he was also a major league scumbag in others, particularly in regards to his jealousy and attempts to discredit the vastly superior Tesla. (Edison managed his accomplishments with little scientific knowhow and a lot of sweat. Tesla was the scientific genius beyond compare; he was also the world's worst businessman, and reading his life story is like watching a slow motion train wreck.

There was a great deal of money in the AC/DC battle of the time. The world was just starting to get wired. The "powers that be" initially had their money on DC, and when Tesla proved that AC was better, they had to steal his ideas and not give him credit to avoid the patent problems. That required a public relations battle, which Tesla lost big time. Hence, most people today don't have a clue who Tesla was. But once you know Tesla, you'll never feel the same way about Edison.

I love biographies. For anyone interested in Tesla I recommend the book that may be found at http://www.netsense.net/tesla/frames.html
I don't think you'll find any enlightening discussion on progressive vs interlaced, however :-)

You're arguing on a false assumption. Just because I didn't mention Tesla, doesn't mean I or others don't know all about him or how he was treated by history books. Him and hundreds of others. The real question which you ignore is WHY are you injecting Tesla into the forum and attacking Edision?

I hate to tell ya, but since you always seem to get personal and seem to look down on us mere mortals like now you finding it necessary to lecture us on Tesla saying dumb things like: "Most people, like yourself, blindly believe the history books about Edison", and other self-serving crap you write I'm guessing you do it to give your ego a much needed massage.

You remind me of another peevish character that just left in a huff for the third or forth time running back to the cow pasture. He like you have this aura where you try to project YOU know something others don't. After awhile it gets annoying like your constant reminding 'I have spent the last 30 years doing ' blah, blah, blah. Give it a rest John. You tend to pontificate. That isn't the sign of an "expert" at least not any I care to listen to, rather more that of a braggart.

But I learned a lot from the various websites posted. I knew about Tesla and some of his work, but not nearly all of it. I also knew Edison was a cad and stole many things from many people, just as Bell, Ford, and others credited with great inventions due to their position rather than brilliance. I personally knew the widow of Philo Farnsworth and know how their family has felt at the credit for the invention of the television being taken from him; I can only imagine how others might feel about this sort of thing. But, credit stolen is a common thing...but that don't make it right.
That said, I sure wish you two would calm down at each other. You are both respected here, and arguing at personal levels like you do makes us all a little uncomfortable. Billy, one comment regarding the whiner that grazes elsewhere; at least John has a great deal of credibility where the other does not. John, Billy may or may not have the book learning (I dunno if he does or doesn't) but he is usually very well informed. Shake hands, will ya, guys? :-)
Seriously, thanks for the history lesson.

Point taken.

I got a good question for you SPOT. I bet you could give us a few good resources for NATIVE American history. That's one area where for sure the American history books are very slanted in one direction.

In a similar vain, its curious how people get ticked off with use of some words or bringing up some indviduals. For example shortly after the events of 9/11/01 in some newsgroup someone took exceptional dislike to the use of us yanks using the word Americans. He pointed out that as a Canadian he too lives in North America, but he didn't want to be associatred with those living in the states.suggesting we shouldn't claim the whole continent as ours by using Americans. I never thought of it before, but he does have a point considering Canada is a larger land mass. ;-)

Philo Farnsworth... there is another guy that got totally ripped off in history. It is amazing how many people in the TV biz have never heard of him either. We owe a lot to Philo and Nikola, but due to the likes of Edison and David Sarnoff, they have been banished into obscurity. What a shame. Spot, I think it's great that you actually knew Philo's widow.

John

Pem Farnsworth sat on a theatre board with many members of the arts community in Utah, most of their family still is living in Utah. I believe Mrs. Farnsworth is still alive, it's been 6 years since I last saw her in person, but she was at the Broadcast Awards here in Utah back in November 2002. The mountain peak above my head is called Farnsworth Peak, as it's where all the broadcast repeaters receive and transmit. Interesting site: http://www.philo75.com/ and has streaming vid of Pem.
As far as Native history.....boy, is there a lot mis-written in the past AND present. Sometimes it's hiliarious, other times it's enough to anger anyone.

I'm not sure anyone ever answered the original poster's question. Very early on in this thread, the assumption got made that TV is interlaced, so why would you ever need to de-interlace or change to progressive? As a result, no one answered the question posed by the original poster.

I do not have complete answers, but here are some thoughts:

Some newer, high-end video cameras capture video progressively (24p mode). If you ultimately want to put this on some sort of videotape and view it on a TV set, I think you need to render it as interlaced. However, if you are putting it on DVD, DVD players have the ability to store individual frames (for film) and then do pulldown (something that got omitted from the disucssions above) whereby 24 fps progressive (or 24 fps film, which is, in essence, progressive) has frames duplicated and weaved into alternate fields to get to the required NTSC 29.97 fps. Thus, if I were lucky enough to have a 24p camera, and I was going to create a DVD, I don't think I would ever render as interlaced. I would render as progressive. Also, if I were rendering stills, as is the original poster, and my output was going to be on DVD, it might be very interesting (and correct, I think) to render as progressive.

Is this correct? I think so, but I haven't done it, so someone who has should either correct my statement or confirm it.

You are correct, but interlacing doesn't necessarily need to be done anyway if it's never going back to tape or if the editor doesn't have a 24p cam, as all DVD players will interlace a progressive DVD. Question is whether they do it correctly or not. If it's shot with true progressive scan camera, such as the panny 100, then it never needs to be interlaced again. Mike Chenoweth and Dr. Dropout gave me some wonderful 24P footage to play with, and I've rendered it as 24P, and 30P, and 60i. My DVD player interlaced the two P formats just fine, and the 60i was the same, but it had lost some of it's crispness in the interim, due to interlacing.

I've rendered it as 24P, and 30P, and 60i. My DVD player interlaced the two P formats just fine, and the 60i was the same, but it had lost some of it's crispness in the interim, due to interlacing.

If the P formats look good, then that's the way to go because you can get 29.97/24 = 1.25 or 25% more on a DVD if you put the author directly with the progressive footage. This is a BIG bonus.

Lots of confusion about the DVX100. When it shoots in 24p or 25p in the PAL version it's still an interlaced field sequence, difference is the two fields are taken at the same point in time. The NTSC version does either 2:3 or 2:3:3:2 advanced pulldown.
It does it this way as it's the only way to record to tape that can be read back into a NLE. So what you end up with is the same as would come out of a telecine. You can then reverse telecine the footage to produce a tue 24p video. You cannot PTT with this, only way to move it around is on HDD for say transfer to film or to DVD. Footage in this state is about all that I can think of that might need interlacing if you wanted to PTT.

What may be the cause of the original question is in PS when saving to some formats it asks if you want to save interlaced. Never worked out just what they are on about here, unless they mean some way of saving a jpeg so the image appears faster.

...didn't Tesla invent the stapler..? ...I use it all the time...

Clipman, I know you were kidding, but for what it's worth...

Brass paper fasteners were introduced in the mid-1860s, and by 1866 George W. McGill had developed a machine to insert these fasteners into papers. The first stapling machine with a magazine that held a supply of preformed wire staples that were fed automatically to the staple-driving mechanism was patented in 1878.

The stapler as we know it didn't arrive in offices until 1914. The first ones used loose or paper-wrapped staples and were hard to use. The breakthrough model, a simplified version from the Boston Wire Stitcher Co., came out in 1923. It was soon followed by another innovation: staples that came glued in a strip. The new office devices were called Bostitch staplers, a short form of the company name. The name became so widely known that the company changed its name to Bostitch in 1948.

Although, I believe Edison eventually took credit for it. :)

John