Interlaced Field Dominance Confusion

[David Roth weiss]

All HD is either upper field first or progressive.

All Hollywood movies are encoded from progressive sources (i.e. film or 24-frame video) and are encoded as progressive MPEG-2 for SD DVDs.

It is up to the compressionist to make certain fields are set properly, as Compressor does not always properly set fields automatically, as you saw when it decided your 1080i material was progressive.

David Roth Weiss
Director/Editor
David Weiss Productions, Inc.
Los Angeles

POST-PRODUCTION WITHOUT THE USUAL INSANITY

[Rafael Amador]

When we talk properly about NTSC or PAL, the concept of the field dominance or field order, its doesn’t exist. The odds lines of each frame are scaned first and the even lines are scaned after. The field dominance appear with the digital video.
In any digital film (QT, MPG2..) the field order is not an issue as long as the fields are readed in the correct order. So you can have a DV movie “upper-first” and FinalCut will read it properly if you set “upper-first” in the clip stting. So the matter is that the field-oder is properly interpreted by the application that has to manage them.
One advantadge of sending things to Compressor from the FC time-line, is that Compressor reads directly from the FC sequence the field-order so you don’t need to tell Compressor that.
The digital video has bring many solutions to the problems of the analog video (Color-framing, always components, etc) but the developers IMHO has bring us a mess with the issue of the field-order. After reading and asking a lot, I still not see any technicall reason for having some codecs working upper-first and some others lower-first.
As David says, the Holliwood movies are scaned from film, but they are converted to interlaced video prior to make a interlaced MPG2. Of course you will never see interlacing artifacts because there is not time difference in beteen those fields.The average DVD players do not read progresive.
cheers,
rafael

[David Roth weiss]

[rafalaos] “The average DVD players do not read progresive.”

Well, I hate to disagree, but actually nearly all set top DVD players manufactured after 2004 read progressive. And, to be absolutely accurate, progressive source video (such as from film) is normally encoded on DVD as interlaced field pairs which are reinterleaved by a progressive player to recreate the original progressive video.

Hope this clarifies some things…

David

David Roth Weiss
Director/Editor
David Weiss Productions, Inc.
Los Angeles

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A forum host of Creative COW’s Business & Marketing, and Indie Film & Documentary forums.

[Rafael Amador]

You are right David. The problem is that if a DVD is played progresive, we would need a monitor that can cope with a progresive picture.
rafael

[Shiloh Heyman]

Thanks David & Rafael,

I think you have cleared this up for me.

So if I understand correctly, when encoding the mpeg2 file for most compatible comercial DVD, the field dominance makes absolutely no differance as long as it is interlaced with the field dominance of the origional footage. Encoding to progressive mpeg2 for DVD may only work for players manufactured after 2004 playing through interlaced TVs, and would not be best for compatability of all DVD players out there.

If I am working with progressive footage, is compressor the best (highest quality) way to interlace it for best player compatability, or would after effects be better?

Thank you again!

Shiloh

[Rafael Amador]

[Shiloh] “the field dominance makes absolutely no differance as long as it is interlaced with the field dominance of the origional footage”
You don’t need to keep the original dominance. You can tell Compressor to change the field order. What is necesary is that Compressor knows the correct field order of the film. You can bring to Compressor a lower-first and get an MPG2 upper-first, but make sure that Compressor knows is lower-first.

[Shiloh] “Encoding to progressive mpeg2 for DVD may only work for players manufactured after 2004 playing through interlaced TVs, and would not be best for compatability of all DVD players out there.”
I’m not much sure about this but I guess that if you play a progresive DVD in a NTSC or PAL player, the player interlace the picture to output an standard NTSC or PAL signal that they must be interlaced.

[Shiloh] “If I am working with progressive footage, is compressor the best (highest quality) way to interlace it for best player compatability, or would after effects be better?
“
The progresive footage has an advantage, you can read it as progresive or interlaced, and if you read it as interlaced, it doesn’t make any difference the field order. The two fields have been captured in the same moment so there is not motion difference in between both. If you bring a progresive clip to Compressor you can treat it as progresive, upper-first or lower-first. You can check this in FC. Play a progresive image in a progresive time-line. Them set it in an upper-first and in a lower-first time-line. You will see not difference in the screen.
Cheers,
rafael

[David Roth weiss]

[Shiloh] “If I am working with progressive footage, is compressor the best (highest quality) way to interlace it for best player compatability”

Whoa!!! Hold on a minute. I can see how you might infer that, but under no circumstance should you “manually” interlace your progressive video. You should set for progressive output and Compressor will encode identical interlaced fields and this will playback properly through all players.

In shorthand, progressive players have a chip onboard that deinterlaces the identical fields creating a true progressive frame and earlier non-progressive players just play back interlaced. Its actually a bit more complicated than that, but thats what you need to know. You must use a progressive-scan display in order to get the full benefit of a progressive-scan player, but the DVD still displays properly on an interlaced monitor, just at interlaced resolution, which is “in theory” about 50% that of true progressive video.

Does this make sense???

David Roth Weiss
Director/Editor
David Weiss Productions, Inc.
Los Angeles

POST-PRODUCTION WITHOUT THE USUAL INSANITY

[Chris Poisson]

You may find this thread helpful. There’s a lot of talk about fields in it.

https://forums.creativecow.net/thread/8/949009

Have a wonderful day.

[Ken Owen]

David,

Thanks for your insightful posts from last fall. I’m just finding this thread and want to be triple-sure I “get it.”

I make DVDs for DePauw University using Mini DV tape sources and came across a discussion on another board that, for a DVD to play properly on a progressive scan player, it must be flagged as “progressive” when the file is created. As I’ve made, literally, hundreds of files… I immediately broke into a sweat thinking I’ll have to revisit the woodshed.

My files default to “bottom first” in compressor out of FCP, and the resulting discs are replicated, so I’m trying to make these as good as I can (as I suppose we all are).

Do I have it right?

And thanks for any insight you can provide!

Yours,

Ken Owen
Executive Director of Media Relations
DePauw University
Greencastle, Indiana

[David Roth weiss]

I would ignore it and move on Ken. Though I have no idea of the context of the other post, my guess would be they were referring to material that originated on film or true progressive 24p video, and they are discusing flaggng to insure that the player does the in fact play as true progressive.

David Roth Weiss
Director/Editor
David Weiss Productions, Inc.
Los Angeles

POST-PRODUCTION WITHOUT THE USUAL INSANITY ™

A forum host of Creative COW’s Apple Final Cut Pro, Business & Marketing, and Indie Film & Documentary forums.