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23.976fps.. 29.97fps.. ivtc

 
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Chung



Joined: 04 Mar 2002
Posts: 79
Location: North Carolina, USA

PostPosted: Mon May 13, 2002 3:24 pm    Post subject: 23.976fps.. 29.97fps.. ivtc Reply with quote

Usually, unless it's actually FILM.. I just rip to 29.97fps and run it through Graft's telecine filter... but recently, I've been playing with, I guess, full IVTC. Wonder if my process is right.. tried following what I could find. I use the guide on flexion for a lot of things.. and follow it's Film 89% rule fo dvd2avi conversion.. but what about the 29.97fps stuff.. How does one tell when you can ivtc it? if anything.. does it come down to watching frames and catching to see if there's a 5th frame repeated? or is there a more 'correct' way?

Been thinking about putting out BGCrash eps.. remember there were those... other... eps posted a while back.. thought maybe a good jap/eng rip could be appreciated? just remembering those original BGC eps I did.. there were bad rips and I know it.. but oh well, it was my first.

So if anyone knows about IVTC and/or frame rate reduction, anything speak up with?

--Chung
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user



Joined: 19 Feb 2002
Posts: 72

PostPosted: Tue May 14, 2002 12:06 pm    Post subject: Reply with quote

I don't bother with IVTC now anymore since my past experiences with it didn't seem to show much improvement. But in theory (and AFAIK) IVTC should give you a smaller encode as well as remove much of the interlacing (one guide I read suggests to always do IVTC first and then use a deinterlace filter if you still see interlacing afterwards.)

I used to use Tmpgenc's IVTC, which I found extremely slow but decent. Vdub/Nandub can also do IVTC, but when I was encoding Seraphim Call I found that motion looked jerky after applying it.
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Chung



Joined: 04 Mar 2002
Posts: 79
Location: North Carolina, USA

PostPosted: Tue May 14, 2002 4:58 pm    Post subject: Reply with quote

Seraphim eps were VHS? they look good, btw... better than most VHS caps I see Smile

Well, here's the whole thing I was thinking with using IVTC.. if you have 6 less frames per second, and you keep the same data rate.. which being so should be the same filesize.. that would give more data to each frame so you'd have higher quality, right? That's my whole incentive to using it, if I do.. if only I knew when it's proper to use it.

DVD2AVI seems to do well, for the SVCD and DVD stuff I do sometimes.. for avi's.. well, I've just started playing with it.. so haven't gotten there yet. but the output seems pretty good.
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user



Joined: 19 Feb 2002
Posts: 72

PostPosted: Wed May 15, 2002 12:04 am    Post subject: Reply with quote

Heh, thanks... yeah, SC was from VHS. I had really good source tapes, which helped tremendously. Smile

I think I'm forgetting something very basic about encoding, but is the data rate constant? I thought for SBC and divx4+, Nandub and/or the codec decides how much data to give each frame, depending on the amount of motion in the frame and whether it's a keyframe or not... and thus the specified data rate is just the maximum that the codec can use, but not a requirement to constantly encode at that rate.

But of course, having 6 less frames per second will mathematically result in a smaller file or a file that's the same size but with more data in the frames. I just don't know if it's possible to encode to a fixed file size.
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Chung



Joined: 04 Mar 2002
Posts: 79
Location: North Carolina, USA

PostPosted: Thu May 16, 2002 6:16 pm    Post subject: Reply with quote

Well, from the numerous encodes I seem to have been doing lately, I can guess a filesize and the rate needed.. or vice versa.. sometimes though, I see a really odd one where the result is 20mb off or something.. dont understand that one. About SBC, no idea.. never used it.. but from what I remember reading.. it switches low/high motion mpeg4 to acheive a better rate for those particular scenes? I really dont know.. only read briefly about it once.

Guess I'll just have to play with ivtc and encoding some more.. need to figure out how to tell when to use it or not... I guess obviously, not when it's pure progressive.

--Chung
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user



Joined: 19 Feb 2002
Posts: 72

PostPosted: Thu May 16, 2002 8:15 pm    Post subject: Reply with quote

Chung wrote:
About SBC, no idea.. never used it.. but from what I remember reading.. it switches low/high motion mpeg4 to acheive a better rate for those particular scenes? I really dont know.. only read briefly about it once.

Yeah, as far as I know SBC does codec switching per frame if it thinks that's optimal, hence the need for 2 passes when encoding.
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manwithbeard
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PostPosted: Wed Sep 11, 2002 12:58 am    Post subject: Reply with quote

I've noticed a big difference between 23.976 IVTCed and the full 29.976FPS Deinterlaced. 24FPS IVTC's quality is much better, because like said, reduces the number of frames to be compressed for the same bitrate. As for deinterlaced full 30FPS, you are looking at first adding the deinterlacer, which can result in a quality drop most of the time, and then you are compressing more frames.

When it comes to Anime, Inverse Telecline is the way to go, because they are almost always mix mode. Now, there are sometimes when IVTC fails, because they have too much interlacing and thus would need a deinterlacer of some sorts (I understand Eva is like this). If you want to know when to IVTC, just check what DVD2AVI says. It'll say whether it's FILM or NTSC. Sometimes, It's 75-85% NTSC and 25-15% Film and sometimes it's just NTSC. In anycase, I find making an AVS file with the decomb.dll in the plugins works for whatever process you make. SVCD or AVI. Though, with SVCD, you really don't have to do either deinterlace or IVTC, but it's quality is better. Personally, I make things easier on myself and use Gordian Knot's AVS creator and just open that in virtualdub or TMPGEnc. (You may want to open it in notepad first and delete all the lines with # in front of them. Though these are ignored, you have a better chance of getting an avs script error if you leave them in.) And for SVCDs, I just use DVD2SVCD program. It's great like it is. Longer way would be to use [Like mentioned.] TMPGEnc's IVTC, by opening the d2v file in it and settings. There's a nice long walkthrough on doom9's site explaining both easy and manual way.

In the long run, you want to IVTC, only deinterlace when IVTC fails. Always try to IVTC before deinterlacing.

As for captured VHS to other, just set your framerate with your capture card. If your capture card doesn't have an auto deinterlacer... it sucks. Personally, 15fps works for captured anime. Since it's animation and actually runs on a less frame rate. Unless of course you are planning on doing VCD/SVCD, then chose 23.976fps and just convert the captured video in TMPGEnc or DVD2SVCD (with the avi2svcd option) using TMPGEnc or CCE. Since they have to be 23.976/29.976. (If your capture card sucks like mine, you probably would want to add a few filters and choose VCD.)

Now, if you got a hold of interlaced avis... You are pretty much set on using deinterlacer. Decomb doesn't help at all. Neither does TMPGEnc's. I've tried both. Blend fleids in Virtualdub and DVD2SVCD works pretty good. I had a good chance to test it on a Rurouni Kenshi OAV set I got in a trade. (First converted to AVI and my computer crashed, then converted to SVCD, because well, it's a cool anime and I have a DVD player that plays SVCDs.)
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