IVTC questions

The old Video Software Help forum, left visible as an archive.

IVTC questions

Postby rustjive » Fri Aug 09, 2002 3:56 pm

I've read Ermac's guide quite a few times, but there is one point that he doesn't seem to make clear that I'm having a logic block (like a....brain freeze) with in my head.

It's obvious that inverse telecining when exporting is a big deal in terms of saving space or what not, but Ermac points out that it's easier to edit in the format as well, probably as you don't have to deal with the extra fields. However...

How does one do that when going through AVISynth?

I'm not a huge programmer that has delved into the innards of the thing, but my understanding of it, and from what I've seen, it seems to be similar to VFAPI in that it's a frameserver, tell it what frame you want, and it'll dredge it up for you, although it's a bit more efficient and troublefree than VFAPI itself.

From the other posts I've seen on the forum about IVTC-ing, it seems that everyone has their own video source, but if all I've got is VOBs, and just want to run it through AVISynth without actually hard-encoding it, how would I go about that, or at least to the point where Premiere stops displaying those overlaid fields?
rustjive
 
Joined: 05 Aug 2002
Location: MA

Postby jbone » Fri Aug 09, 2002 4:09 pm

Inverse Telecining is the process of restoring progressive 23.976fps source from interlaced 29.97fps source.

When you make your D2V project files, set DVD2AVI to "Force FILM" so that your source will be 23.976fps. This way, you can edit it at 23.976fps, and you can also create an end-product which is 23.976fps. Thus, you won't need to worry about inverse telecining, since your source will already be at FILM's framerate - most animation is produced at 23.976fps, so you won't have to worry about losing anything.

If you're using 23.976fps source footage and it's coming through with interlacing, then there source itself is interlaced and you'll have to either use an AVISynth plugin to remove the interlacing, or just deal with the interlacing through the editing stage and reduce it in post-processing with a similar plugin for VirtualDub.
"If someone feels the need to 'express' himself or herself with a huge graphical 'singature' that has nothing to do with anything, that person should reevaluate his or her reasons for needing said form of expression, possibly with the help of a licensed mental health practitioner."
User avatar
jbone
 
Joined: 12 Jan 2002
Location: DC, USA
Status: Single. (Lllladies.)

Well...

Postby rustjive » Fri Aug 09, 2002 4:58 pm

Well, that worked out well, but a sorta-related followup question about Premiere:

Now that the it's coming off the avs as 24 frames, I've realized that the DV editing that Premiere uses on default (well, it's the highlighted project format) doesn't support the 24fps (as Ermac pointed out). The preloaded project options in Premiere offer DV, Video for Windows and Quicktime as options.

The question is, is there any difference while in editing if I choose Video for Windows or Quicktime (unlikely) instead of DV? And will either of those support the 24fps of film?
rustjive
 
Joined: 05 Aug 2002
Location: MA

Postby klinky » Fri Aug 09, 2002 5:07 pm

VfW is better, if you choose Quicktime you will have to export in Quicktime :shock: .

Of course you can change your project settings later I would not reccomend it.

Use Video For Windows and set the frame rate to 24.


~klinky
User avatar
klinky
 
Joined: 23 Jul 2001
Location: Cookie College...

Postby jbone » Fri Aug 09, 2002 5:08 pm

I always use Video for Windows, and I often edit with a 24fps timefase.

I haven't played with DV, so I can't really talk about the pros and cons of using it (aside from the fact that it's not lossless, which is a con).

For exporting a master post-editing, you'd probably want to use Huffyuv over DV, anyway, unless you have hardware that does DV in realtime. Huffyuv is lossless, but DV is lossy (meaning you'll lose some visual data). DV isn't <I>nearly</I> as lossy as, say, MJPEG or MPEG, but if you re-encode DV enough times you will most definitely see degradation.
"If someone feels the need to 'express' himself or herself with a huge graphical 'singature' that has nothing to do with anything, that person should reevaluate his or her reasons for needing said form of expression, possibly with the help of a licensed mental health practitioner."
User avatar
jbone
 
Joined: 12 Jan 2002
Location: DC, USA
Status: Single. (Lllladies.)

Yet another...

Postby rustjive » Fri Aug 09, 2002 5:46 pm

I'm getting interlacing in Premiere, and it very well could be because of the original video source, but I just had to check everything out/make sure/bother you all again.

My d2v is Forced Film, and in most cases there isn't any interlacing, but I'll get back to that. Premiere still shows telecining, although DVD2AVI doesn't, when I do it frame by frame. What DVD2AVI DOES do is that there are some parts that are interlaced, or appear to be, yet, it's only for certain parts: i.e. If Ed were talking, his mouth would be interlaced, yet none of his body would. This might be correct for how interlacing works, and I'm not aware of it, but what's curious (and this might be where my knowledge is sorely lacking) is that in certain frames of movement, interlacing is visible (again, in parts), yet they aren't the 'intermediate' frames of telecining. By 'intermediate' I mean the frames, telecined, where the overlap occurs between frame one and frame two.

Does this mean that the source itself is interlaced?
rustjive
 
Joined: 05 Aug 2002
Location: MA

Or...

Postby rustjive » Fri Aug 09, 2002 5:48 pm

Or (more likely) does DVD2AVI not advance frame by frame when you click the < and > signs?
rustjive
 
Joined: 05 Aug 2002
Location: MA

Nevermind

Postby rustjive » Fri Aug 09, 2002 5:51 pm

Answered my own question. Why doesn't DVD2AVI just advance frame by frame?

*sigh* stupid interlaced video
rustjive
 
Joined: 05 Aug 2002
Location: MA

Postby klinky » Fri Aug 09, 2002 7:31 pm

Well it's fairly confusing but...

Pretend TVs display 60 fields a second..

and you have 30frames per second video.

a field is half a frame, either the even or odd lines of the video.

so on a computer since it is progressive and CAN display 30fps, you can see the whole frame. But on a TV you would view it fields at a time.

okay well that's sorta confusing..

What telecining does is mesh, two frames together to make a whole new frame.

So take the even lines from frame A and take the odd lines from Frame B and put then together. If you view this on a computer, then it looks horrid, since you have two frames mangled together, on the TV however you don't notice it because it only displays the even lines.... then the odd lines. So you don't see the entire frame in one TV refresh as you would on the computer. Telecining does this in a certain pattern, and there is no set standard way of telecing video, so some people may mix and match differently, then others...

So DVD2AVI is forwarding at a frame at a time, but the frames have been merged.

As for your problem. If you try FORCE FILM in DVD2AVI and you load the file into Premiere or something else(also make sure your Premiere project is not setup for fields, check Keyframe & Rendering, make sure it's set to 'No Fields'), then your best bet is to just leave it at 29.97 and use a area-based de-interlacer, or you can leave it at 23.98 and do the same. Just it may not have ivtc'd it properly if you still notice lines and may result in jerkiness or something ... I don't know :p

I usually don't deal with ivtc since I've never gotten it to work properly.

~klinky
User avatar
klinky
 
Joined: 23 Jul 2001
Location: Cookie College...

Postby klinky » Fri Aug 09, 2002 7:38 pm

Oh yeah and I think Ed is a girl, not a guy.


~klinky
User avatar
klinky
 
Joined: 23 Jul 2001
Location: Cookie College...

Postby ErMaC » Sat Aug 10, 2002 12:04 am

First off, don't use the Force FILM option in DVD2AVI because on 95% of anime DVDs it will not produce a stream which is really progressive.

Instead what you want to do is in your AVS script, include the lines that I talk about in my DVDGuide to IVTC - the ones that use DeComb. DeComb will IVTC in realtime as you work.

And BTW - the reason why, when you're in DVD2AVI itself, it doesn't go 1 frame at a time is because the < and > arrows are moving between GOPs, not frames. Whenever you make a cut with the [ or ] buttons, it must be done on a GOP, and so the author just made the < and > buttons scan between the start of GOPs.


Now your other problem is editing with that 23.976fps footage in premiere. The biggest problem you will face is that Premiere does not support 23.976FPS! It will suppoer 23.98, or 24, but it cannot measure FPS into the thousandths place. What you should do is add the following line into your AVS script:

AssumeFPS(24)

This will basically set the framerate bit on the video to be 24fps, thus speeding it up by .1% but giving you an even framerate. Why 24 and not just 23.98? Well Premiere also has this thing called a timebase - and Premiere has timebases for 30fps, 24fps, and 29.97fps - but not 23.98 - but means that if you edit in 23.98fps and set your timebase to 24, your previews will look out of sync because your framerate is losing sync with the timebase (the timebase measures what frames go where on the timeline, or the distance on the timeline that each frame should take up). By working in 24 you maintain parity between the framerate and timebase.

However this leaves those of us with TV as our desired destination in a quandry. How will we get 24fps back into 29.97FPS? The best way I came up with was to shrink your audio ahead of time.

Open up your WAV file in SoundForge and do a TimeCompress/Expand and change the length of your WAV file to be exactly 99.9% of its original length. Or, if you do not have soundforge and want a free version, us BeSweet and its GUI which can adjust audio to compensate for framerate differences. I've never tried this but AbsoluteDestiny has said that it does work and he's the authority here on audio so I'd ask him to elaborate.

Anyways, once you've got this shrunken WAV file, you can edit with that in your 24FPS timebase. Then once you're done, export it without audio, merge your original audio in with virtualdub (by going WAV Audio) and then under VDub go "Change Framerate" and select 23.976. This will then have your audio and video back in sync, and tada! you can then Telecine it back into 29.97fps.

This is the exact process I used to do Evil Light version 2, which was edited all in progressive with the audio stretch method.
User avatar
ErMaC
The Man who puts the "E" in READFAG
 
Joined: 24 Feb 2001
Location: Irvine, CA

Postby klinky » Sat Aug 10, 2002 12:42 am

ahh yes..ermac the smarty smarty man..


;)

~klinky
User avatar
klinky
 
Joined: 23 Jul 2001
Location: Cookie College...


Return to Video Software Help Archive

Who is online

Users browsing this forum: No registered users and 0 guests