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Progressive / Interlaced, field order?

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Hey everyone, just a little video help question for anyone who can assist.

Currently I'm working on a Superman II Donner fan edit. After backing up my PAL copy of S2 TRDC on my hard drive I converted the VOB files to an "interlaced mpeg2 movie file" using TMPGEnc. I selected "top field first", even though the source type is "progressive", (which I always understood to not require a field order placing).

I’ve been editing it over the last week in Ulead Video Studio. I’m breaking it up into sections so not to be too taxing on my computer. However when I export my edit the picture at times gets a little scrambled, resulting in tiny pauses. Mostly evident in fast motion scenes. It's difficult to explain without knowing the correct terminology, but the pixels just appear shifted at times.

I found this problem to be easily corrected by changing the field order in the project settings to "frame based" or "lower field first".

This has confused me due to the following:

- Firstly the file was encoded as "top field first", so how could rearranging it during the editing stage help?
- Secondly I thought computers tend to not show incorrect field order placing, that this can only be seen on a TV monitor.
- Finally, in the past when I’ve encoded files with the incorrect field order, the resulting effect has been jumpy picture, not this scrambled picture.

Any information with regards to this would be much appreciated.
Forever a Christopher Reeve Superman Movie Fan.
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Well, ya got me confused.

Dvds need to be playable to interlaced sets, so even though they are stored as solid frames, the hardware will think of them as if they were two interlaced fields stored together, sortof. Which is kinda confusing.

1) Uhhhhh....

2) Computer monitors are normally run progressive. So, you'd want to playing both fields as one frame. And your player cooperativly does that. But you'd still be going one line at a time. Playing the wrong field first means that line 2 goes at the top, line 1 below that, 4, 3, 6...

So that part actually makes sense to me.

3) That's weird.

I don't get the scrambled picture. I would think maybe ripping them and fixing GOP errors, like in ADM's editing guide might fix it. But you say changing it in Premier worked. I don't know if you need to fix GOP errors if you convert VOBs in TMPGEnc, anyway.

Are you usually working in NTSC? Maybe that's the difference. NTSC generates extra frames-per-second by duplicating fields. That takes 24 fps and fakes the framerate up to 30, that makes little pauses. Pal just speeds it up from 24 fps to 25 fps. (Both methods suck). But if you normally watch & work in NTSC, you wouldn't really notice that.

Hmmm... Maybe top field first is the wrong setting in TMPGEnc, and Premier is fixing it? But that still doesn't explain #3, unless, like I say, you're used to NTSC.

On the other hand, are you sure your PAL source doesn't have interlacing in it? Sometimes happens if they convert from NTSC to PAL. (It shouldn't be that way, anymore, ever, but it still happens). I'm about to go look up a thing that'd tell you. I'll get back to you in a day or two (or...), if no one comes along with better answers.

Hope I'm not wasting your time, in the meanwhile.

You did say "any information", right?

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Originally posted by: Ollie
Hey everyone, just a little video help question for anyone who can assist.

Currently I'm working on a Superman II Donner fan edit. After backing up my PAL copy of S2 TRDC on my hard drive I converted the VOB files to an "interlaced mpeg2 movie file" using TMPGEnc. I selected "top field first", even though the source type is "progressive", (which I always understood to not require a field order placing).
I'm lost already.
The MPEG-2 on the DVD will be progressive, so why convert to interlaced? (And I'm pretty sure that progressive video should always be encoded top field first.)

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Well as far as I'm aware "field order" is irreverent to progressive films.

However TV can only display in interlace, so the progressive DVD must hold tags as to how to process in interlace mode.

I'm sure there's someone out there who can add something further to this.
Forever a Christopher Reeve Superman Movie Fan.
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I might get something wrong, here, or omit something... I've tried to weed out the duplicated explanations, but probably didn't get them all.

And this might not answer any of your questions. But just to make sure we're talking about the same things...

It gets messy, because "Interlaced" has different meanings. So does "Telecine", and "Progressive".

It depends on whether you're talking about the video itself, or the playback.

Progressive can mean progressive playback - fields faked into frames, for instance. Or film played 24 fps on a computer screen, but the screen is refreshed more often than 24 fps. LCD could also play 24 fps progressively, maybe Plasma. I imagine Progressive could be applied to just popping a frame up there, instead of one row at a time, or mean drawing the frame top, to bottom, without going by fields.

Or progressive can mean progressive video. such as film stored as frames of film, without extra fields. Or it can mean interlaced videocamera footage. Or it can mean CGI done at 25 fps (PAL) or 30 fps (NTSC). Basically it means not-interlaced. (Though vidcam footage is interlaced, it's stored and flagged as frames, not sure about tff/bff). But its still played interlaced on interlace sets. Perhaps its best to say Progressive video means you aren't storing deliberatly-duplicated fields.


Interlaced sets draw the odd lines of the picture first (top field), then the even. The idea is that if picture was drawn, on a picture tube, by a beam lighting up phospor-dots, a frame at a time, at 25 fps, or 30 fps, you would see a heinous flicker. So you draw odd & even separately. That's one definition of "interlaced".

Videocamera footage is recorded one field at a time, 60 times per second, and that's also called "interlaced". And so is "hard-interlaced" or "telecined" material where extra fields have been added to the video - to boost 24 fps up to 25 fps or 30 fps. The hard-interlaced video can be videotape, laserdisc, or broadcast. Sometimes, it may be added, inefficiently, to dvd-video or computer-video. (Hard-telecine can be left in a staticy preservation dvd, also).

Dvd video normally has pulldown flags set to indicate the fields to be duplicated, instead of wasting space on duplicated fields encoded into the video.


A DVD player plays interlaced to interlace sets. It looks at the video as one scanline per row. There are as many rows as will be output to the set, of course. The top-field-first or bottom-field-first flag tells it how those rows correspond to playback.


In Pal-land, it will play 24-fps film fast - at 25 fps. Or it will play material that's recorded on camcorder at 50 fields per second. Or it can play an extra field per half-second. Or play a funky source (that's another subject, below). Always played interlaced, to interlace sets, though.


In NTSC-Land, and interlace sets, it will :

1) Output a 30-fps film source one field at a time.

2) Output 60-field-per-second camcorder footage. (Recorded one field at a time).

3) Output the 24-fps film, but also make duplicate fields into extra frames, to bring up the framerate to 30 fps.

In order to do #3, it needs "pulldown flags", to tell it when to duplicate.

4) Output "hard-telecined" material, where the extra fields are encoded into the video, at 30 fps.

5) Output any mix of that stuff. Then there would pulldown flags, and progressive flags, if I'm not mistaken.


I believe the pulldown & progressive flags can be added by your editor, if you chose, or else you can add them with a utility like dgpulldown.


"Telecined" basically refers to scanning film into an analog master, or directly to broadcast form. In NTSC-land, the telecine process automatically adds hard-pulldown, which is the duplicate fields, right in there. The "hard-pulldown" footage is also called "telecined" or "hard-telecined" or "hard-interlaced". (Recordings or cappings from NTSC broadcasts of film will have that hard-telecine from the broadcast). Nowadays they usually scan it straight into digital, without the hard telecine, unless its going straight out to broadcast.

In PAL, telecine is just scanned straight in. Or they can add an extra field every second, to bump the framerate up toe 25 fps. Or it's made from an NTSC-Telecined master then has the "telecine" (hard pulldown) removed by "inverse telecine", which loses the duplicate fields, or they "deinterlace - they either throw away fields, or blend them together, without regard to uniqueness or duplication. They'll aslo deinterlace NTSC camorder footage, or 30-fps CGI.

That can make a royal mess if you want to bring it back to NTSC. The extra field per half-second is easier to fix.

Also there can be phase shift errors, that I don't understand well enough to explain.


If you are starting with hard-telecined material, its usually best to remove the telecine (IVTC or "Reverse Telecine"). Funky-Pal, well, can become an advanced subject...

One day I found... 10 years had got behind me. Next day was worse.

 

Download  shows from Cable DVR (Updated! Yes, it needs a rewrite, but it's worth slogging through, anyway).