What’s wrong with interlaced footage?

[Michel Satoer]

Hi everybody.

Let me introduce myself, I’m a motion graphic designer from the Netherlands (you can see my work on www.satoerdesign.nl if you like) and have a history as ENG cameraman and editor. I’d like to take my old profession to a next level and want to incorporate more cinema style footage in my productions. Basically I fell in love with the footage from Philip Bloom and ordered a EX1 and Letus extreme for a upcoming production (still waiting).

One thing that I don’t understand with cinema-style filming is the urge to shoot progressive. But maybe someone can enlighten me. (Besides that, I think this is a interesting topic discussion ;) )
What is wrong with interlaced footage? Why does everyone wants to film progressive? I even read threats de-interlacing footage on footage filmed with camera’s that haven’t got a progressive scan (which means you lose half the resolution :( ).
I know that everyone wants his footage to look like film, and the filmlook is great in case of color grading and DOF. But, isn’t the full frame shooting of film actually a drawback for television usage? Of course great for use in a cinema projector. But I think that 99 percent of the cameraguy’s (and girls ;) ) over here is shooting directly for television. And, a television still projects interlaced footage. That’s 50 half-frames per second PAL or 60 half frames per second NTSC.

As motion graphic designer everything I create (leaders, commercials, animations etc.) is interlaced (unless it’s directly for internet). Animations look so much smoother interlaced then full frame (progressive). It’s like you go from 50 fps to 25 fps (in PAL). And basically it is. Have you seen a simple title roll interlaced and full frame scrolling?

I don’t get it, what’s wrong with smooth footage?

Cheers Michel

[Paul Kellett]

I agree......

[Wes Vasher]

Modern displays are progressive. I would argue that 60p footage displayed on a progressive display looks better than 60i footage on an interlaced display. Certainly 1080 60p is going to look much better than 1080 60i.

I love smooth footage, love it! I hate dealing with interlacing. I like progressive because it makes life easier for doing effects and animation.

[Nick Jushchyshyn]

There's nothing "wrong" with interlaced video itself. Just as you say, it looks smooth and clean. Even in visual effects & animation situations, interlacing is handled quite well by all the pro-grade tools (the exception is roto, where the artist's work doubles for interlaced material).

The "issue" is that, stylistically, many people are striving to look like film instead of video. Film is not interlaced ... so for anyone trying to achieve a "film look" ... interlacing is "wrong".

[Andrew Kimery]

Originally Posted by Michel Satoer

Have you seen a simple title roll interlaced and full frame scrolling?

Yes, the interlaced tends to twitter if the font isn't just right and the progressive has no such issue. ;)

Progressive doesn't just mean 24p. A progressive frame rate such as 60p has 60 complete frames a second which will look just as fluid, and much cleaner, than video that is 60 half-frames a second.


-A

[Petri Kaipiainen]

Certainly 60p would look better than 60i, but there is NO consumer or prosumer cameras in existence which shoot 60p, and there is no delivery medium for such a beast and no TV set is capable of handling it. So this is all just a dream. Has any of you ever seen clean 60p material?

I shoot only interlaced, looks better to me, too. Why duplicate the low frame rate of film???

[John Estcourt]

jvc hd200 records 720 @ 60 p or 50p here in Pal land

[Andrew Kimery]

Originally Posted by Petri Kaipiainen

Certainly 60p would look better than 60i, but there is NO consumer or prosumer cameras in existence which shoot 60p, and there is no delivery medium for such a beast and no TV set is capable of handling it. So this is all just a dream. Has any of you ever seen clean 60p material?

Erm, lots of stuff shoots, handles, and b'casts 720p60 material.


-A

[Paul Gale]

Don't forget if you're shooting for eventual web delivery rather than TV, progressive has many advantages rather than having to de-interlace at some stage and risk titles etc looking bad.

[Michel Satoer]

Of course 60p will look much better then 60i. You double the resolution and keep the frame rate. But if you compare 30p vs 60i, the 60i will look so much smoother.

Originally Posted by Nick Jushchyshyn

The "issue" is that, stylistically, many people are striving to look like film instead of video. Film is not interlaced ... so for anyone trying to achieve a "film look" ... interlacing is "wrong".

So if you’re camera has an 24p and a 30p option you will use the 24p option and then convert this to 30p in post to match NTSC framerate? Just to get that real movie film look?

Originally Posted by Wes Vasher

Modern displays are progressive.

This is an interesting point. How do modern flat screens handle interlaced footage? Do they detect that the footage is interlaced and display an 30i source as 60p by sub-sampling the half-frame’s to full frames? Or do they just de-interlace the footage and throw away half the resolution data. Or, will they output the 30i source just as 30p and you can see the even and odd frames in the same frame (like playing interlaced footage on a computer)
Has anyone did some test? What happens if you send 30p and 30i to a flat screen. Will the 30i look smoother? Has anyone tried (or by accident) to display an 30i source with a reverse field order? So you get that horrible jittering. (2 Frames forward, 1 frame back, 2 frames forward etc.)

[Chris Hull]

Originally Posted by Michel Satoer

Hi everybody.






Let me introduce myself, I’m a motion graphic designer from the Netherlands (you can see my work on www.satoerdesign.nl if you like) and have a history as ENG cameraman and editor. I’d like to take my old profession to a next level and want to incorporate more cinema style footage in my productions. Basically I fell in love with the footage from Philip Bloom and ordered a EX1 and Letus extreme for a upcoming production (still waiting).

One thing that I don’t understand with cinema-style filming is the urge to shoot progressive. But maybe someone can enlighten me. (Besides that, I think this is a interesting topic discussion ;) )
What is wrong with interlaced footage? Why does everyone wants to film progressive? I even read threats de-interlacing footage on footage filmed with camera’s that haven’t got a progressive scan (which means you lose half the resolution :( ).
I know that everyone wants his footage to look like film, and the filmlook is great in case of color grading and DOF. But, isn’t the full frame shooting of film actually a drawback for television usage? Of course great for use in a cinema projector. But I think that 99 percent of the cameraguy’s (and girls ;) ) over here is shooting directly for television. And, a television still projects interlaced footage. That’s 50 half-frames per second PAL or 60 half frames per second NTSC.

As motion graphic designer everything I create (leaders, commercials, animations etc.) is interlaced (unless it’s directly for internet). Animations look so much smoother interlaced then full frame (progressive). It’s like you go from 50 fps to 25 fps (in PAL). And basically it is. Have you seen a simple title roll interlaced and full frame scrolling?

I don’t get it, what’s wrong with smooth footage?

Cheers Michel

i think you say it all with film looks great with color grading and depth of field,but that is film it makes the world look better than it is if you look out of your window in daytime while watching a cinema film on tv the film gives it a magic unreal look.compaired to what you see outside,for me frame rate p alone can not give true film look if i were you i would film using interlaced but i know the progessive craze is here to stay

[Levi Bethune]

I do a lot of stylized effects in my work, and a lot of slow motion and freeze-frame in the middle of action. So interlaced is not really an option for me. Shooting with the JVC HD110, I can select Standard Def 60p recording and have excellent control over my speed while it still looking as smooth as interlaced.

I just can't stand having half the information per frame than I really should. I find myself de-interlacing to get complete information for photoshop, freeze frame, keying, most text... and I don't have to worry about it with progressive footage.

The only real way you can have the fluid motion look of 60i is to shoot 60p. 60i has the same amount of information as 30p, it just doesn't combine half-frames. So if you think 60i looks good, when you shoot 60p, you're actually getting the same information as if you were shooting 120i. When you say 30i, I think you mean 60i. 30i is the same as 15p.

[Heiko Saele]

even read threats de-interlacing footage on footage filmed with camera’s that haven’t got a progressive scan (which means you lose half the resolution :( ).

There are methods of de-interlacing that don't lose resolution, they use algorithms like "motion compensated de-interlacing" and such. Don't know exactly how these work, but they somehow detect jagged edges and correct only when needed.

Interlacing was introduced in the early days of television because the displays weren't fast enough to project 60 full frames per second. Now that these times are long gone and we have plasma and tft displays with HD resolution, there is no reason to use interlacing anymore. I will be glad when I won't have to deal with interlaced footage anymore.

However, I will also be glad when big movie production will start shooting in 48P or 50P or 60P. I don't like 24P/25P too much, but it comes closest to the film look people are used to...

[Glenn Chan]

There are methods of de-interlacing that don't lose resolution, they use algorithms like "motion compensated de-interlacing" and such. Don't know exactly how these work, but they somehow detect jagged edges and correct only when needed.

They do lose something... it's just that they look better than inferior/other approaches.

De-interlacing technically doesn't work since it's trying to make up information that's not in the original signal.

Interlacing was introduced in the early days of television because the displays weren't fast enough to project 60 full frames per second.

I believe they were fast enough, it's just that they want to save bandwidth for over-the-air transmission and it's a crude form of compression. It also has the side effect that there is little visible flicker... e.g. 59.97 fields/second interlaced looks better than the TV scanning 29.97 frames/second scanned progressively. The latter would be totally unwatchable. 29.97/second flashed twice on the other hand would be watchable (much like how 24fps film is flashed twice to avoid flicker). Back then flashing an image twice wasn't really viable since you'd need a frame buffer (and I don't think those existed).

[David Heath]

Originally Posted by Michel Satoer

Animations look so much smoother interlaced then full frame (progressive). It’s like you go from 50 fps to 25 fps (in PAL). And basically it is. Have you seen a simple title roll interlaced and full frame scrolling?

I don’t get it, what’s wrong with smooth footage?

Michel, I think you're confusing a few aspects, and it may be due to a common clumsy use of the word "progressive". Too often it's taken to mean "cinema look", (which it can be) but not exclusively as others have pointed out in the case of 60p.

In practice it should be defined as "entire picture at a time", rather than "odd lines followed by even". And it can mean 24, 25, 30, 50 or 60 frames at a time. And 50/60p have just the smooth footage you want.

Originally Posted by Levi Bethune

When you say 30i, I think you mean 60i. 30i is the same as 15p.

Levi, the official nomenclature got redefined a few years ago to be of the form "576i/25", "720p/50" where the first number represents the number of active lines, then letters to indicate scan type (i, p, or psf), then a number to always represent the no of FRAMES/sec (and never fields) - regardless of whether it is interlace or progressive.

I believe the main reasoning was that it was felt somewhat illogical for it to sometimes refer to frame rates, sometimes field rates, as was the case with 30p, 60i - both referring to the same no of frames.

In answer to the question posed: "What’s wrong with interlaced footage?" then the first comment would be that it is much more difficult to compress well than progressive. The second is that for a given number of lines, interlace will have a lower effective vertical resolution than progressive.

In simplest terms there are three main attributes to a TV system.

1/ No of lines - generally 720 or 1080 for HD

2/Interlace or progressive

3/Motion rate - normally 25Hz or 50Hz in 50Hz countries.

TAKEN INDIVIDUALLY, 1080 is superior to 720, progressive to interlace, and 50Hz to 25, so logically you'd expect to want the 1080p/50 system.

Unfortunately, that is just too technically demanding for most purposes at the moment, and practically one of them normally has to be sacrificed - so the three most common variants become 720p/50, 1080i/25 or 1080p/25.

If the "cinema look" is actively sought, then 1080p/25 becomes the obvious choice, and that's the format that most HD drama etc is being produced in in Europe. If smooth motion is more important (as for sport) then one of the others is better chosen. Much has been written about the relative merits, but in practice most broadcasters seem to be going with 1080i/25, as 1080p/25 can be relatively easily carried over it in psf form. For a sport only channel, 720p/50 may be a better choice.