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The "Farsight" Trilogy DVD Info and Feedback Thread (Released) — Page 2

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Originally posted by: Doctor M
Arnie: Laserdiscs are an interlaced source. You do NOT de-interlace when encoding to DVD afterwards. Therefore the answer is "nothing", Farsight would no doubt have not de-interlaced the movies (unless he didn't know what he was doing).


This is incorrect. You want your final DVD to be a 24fps progressive source. This is what the actual film is, and what a retail DVD would be. It's also fairly simple to achieve with AVIsynth. The Laserdisc is 30fps interlace, which means 1/5th of the data is duplicates of other fields, and an interlace source will not compress well anyway.

Using AVIsynth, you deinterlace to give you 60fps, with 2/5ths of these being unique images. These are the real movie. Taking them, you have your 24fps film. If done carefully and properly, it will produce images practically identical (no blending or sync issues at all) to the original film before it was altered to make the laserdisc. You end up with a better image that will also compress better (preserving more image quality), and doesn't rely on hardware to deinterlace it (which can vary in quality).
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Now I'm confused. While I understand what you are saying, and it's damn cool, aren't DVD's by their nature interlaced (at least NTSC ones)? Hence the Bob/Weave filters in software based DVD players.

Or are you saying you took the Laserdisc, deinterlaced it to get the original frames and then reinterlaced it when encoding the dvd? If so, I'd love to see the AviSynth script you used.

Dr. M

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Most films on NTSC DVD are progressively encoded, no interlacing, to get the 23.976fps up to 29.97fps of NTSC the mpeg2 stream contains flags telling the player to repeat certain fields (3:2 pulldown), but if you play the video on your PC which is has a truly progressive output (your CRT or LCD monitor) the software player ignores the flags in the mpeg2 stream and plays it at 23.976fps.
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***Citizen's NTSC DVD/PAL DVD/XviD Info and Feedback Thread***
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It is possible to encode your mpeg2 at 29.976fps interlaced, but it's not very efficient. Though some retail DVD's are done this way anyway. 24fps progressive video takes up 20% less space and the player can always do interlacing on the fly during playback.

The process of converting from 24fps progressive to NTSC 29.97 is known as telecining. The reverse process is known as inverse telecining or IVTC. There are many ways you can go about IVTCing your video stream once you've captured it off the laserdisc. Two of the more popular ways are (1) using AVISynth filters to do the job, and (2) using Virtualdub's manual IVTC settings. On my own personal projects, I've found using Virtualdub does a perfect job every time. As a rule of thumb, you usually want to run any dot crawl filtering before you IVTC. Most other filters do a better job on the progressive side.

My Projects:
[Holiday Special Hybrid DVD v2]
[X0 Project]
[Backstroke of the West DVD]
[ROTS Theatrical DVD]

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I suppose I stand corrected.
I was under the impression from most of the "conversion to DVD" guides out there that if your source is interlaced you do more damage to the quality by de-interlacing (which is never perfect) and generating a progressive DVD.
It is also unnecessary since the final output device will most likely be a television and therefore an interlaced device.
It is considered preferable to capture, and encode retaining the interlacing and to only use progressive if your source is true film (which a laserdisc is not).
I won't argue (although it does sound like I am) since you guys have done more of this than I have, but I find it hard to believe that so many guides (from reputable sources) are wrong.

Dr. M

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You really want a non-interlaced image for running through filters and MPEG encoding - it'll produce the best quality, and best compression.

Of course it depends on the -original- source. In this case we're talking about a 24fps original source (film)... we don't care what format the laserdisc is in, except to undo the damage they did when making it.
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So for fear of prolonging a conversation that is starting to seem off topic:
Are you allowing your capture hardware/software to IVTC or are you using a decomb/GreedyHMA plugin? I think you said you were using Avisynth so probably the plugin filters.

I'm just trying to get my mind around how you deal with the 2/5ths of the frames that only exist as interlaced, since deinterlacing them is damn hard to do well. You would have to reconstruct them correctly somehow without introducing artifacts.

Again, maybe I don't know what I'm talking about but all I have to go on is other video guides.
I'm starting to be remarkable impressed with what you guys have done. (More than before.)

Dr. M

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Personally I found automatic ITVC filters/plugins etc. on AviSynth & VirtualDub to not be up to scratch, scenes with seemingly no movement they have trouble with whereas if you manually go through the captured file and find the undo settings yourself you can avoid the screwups the automatic removers do.
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***Citizen's NTSC DVD/PAL DVD/XviD Info and Feedback Thread***
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Yeah, sorry Doctor M, but any project worth its salt does an IVTC process first to completely reconstruct the original 24fps film frames.
So farsight did this because he *did* know what he was doing

When the guides talk about 'The source' being interlaced, they mean the original source. In our case the original source is film, whic is 24 progressive frames per second, which was then transferred to laserdisc and made into a 30fps interlaced mishmash.
The IVTC process recreates the original film frames with no quality loss by extracting the matching interlaced halves and putting them back together.

If the 'original source' was video (i.e. it was shot using an interlaced video camera in the first place) then you cannot do an IVTC, and any form of de-interlacing does cause a quality degredation as there are no original progressive frames to get back to.

So for stuff that originated on film, doing an IVTC is a must, for stuff shot on video, you can only get a compromised image by deinterlacing and averaging and so forth.
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Actually I found the IVTC built into the later versions of virtualdub never has a problem. I think it is nice and dumb and just removes based on a set pattern and doesn't try to 'guess' like the various 'automatic' avisynth filters do.
It only gets out of whack when there is an error in the source footage, in which case you just start it again from the problem frame.
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Using AVIsynth's DoubleWeave, followed by Pulldown, worked perfectly for me. You just have to manually figure out which field comes first (since you can't rely on the LD to not have errors), and must also figure out which 2 of every 5 frames are unique (easiest to do in sections with fast motion, since 2 frames will be interlaced, and 2 others will be identical).

Bottom line - it's a pain.
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Okay, this is nothing to do with Farsight's set, but it kind of follows on from the above: how does on-the-fly PAL to NTSC conversion work? Are PAL DVDs generally encoded at 24fps progressive, with the PAL player converting to 25fps? If so, does the PAL/NTSC player apply 3:2 pulldown to get to 29.97 at true speed, or is it somehow still played at PAL's 104% speed?
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All decent film DVDs are stored as 24fps on the disc itself. No DVDs store anything as progressive, it is an interlaced system - but the two fields stored make up exactly one film frame, so the end result is the same really.
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PAL films are generally stored progressive but at 25fps instead of 24fps (no framerate conversion, just plays back faster) with the audio sped up to match the faster playback rate.

Although saying that a fair amount of films on PAL DVD are flagged as interlaced (!) despite them having progressive footage. But not all films on PAL DVD just play back 4.096% faster, my R4 Spirited Away DVD has been framerate converted from 24fps to 25fps, the end result is a sub-standard interlaced picture that doesn't look too good, especially on a PC screen.
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***Citizen's NTSC DVD/PAL DVD/XviD Info and Feedback Thread***
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I've been watching the forum here for a while, and one thing that I've not seen much of, with a few exceptions, are screenshots of the DVD menus on fan-produced preservation of the OT. I've started a thread under the "Preservation And Fan Edits" heading in hopes that people might post screenshots here just for comparison purposes. Hopefully, I am not the only person interested in the stylistic directions that the folks working on these various productions take, so please, if you have a completed fan preservation, post a few screenshots of what your menus look like, as many of these are often little works of art in and of themselves.

cross-posted
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Super Mario Bros. - The Wicked Star Story
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Does this trilogy set have no DVD menu screen?