Confused with IVTC

[hacker_on_fire]

I am confused about a couple of things. I was hoping that you could reassure me about:

1) does pal = 25fps and ntsc = 29.970fps, cos i got a film at 23.97. So what would this be?

2) what is ivtc used for. Also in Doom9's guide it says when you save a dvd2avi project in Gknot to avs IVTC can be activated by choosing it under the Field Operation section & typing a code in the edit mode.

However the edit button cannot be pressed if i select 'Both' under the trim section.

Also i cannot select Inverse Telecine as it does not appear under the field operation.

3) In doom9's guide it says if you perform IVTC, you must change the framerate. How? & Why?


I know its a lot of questions, but this has been in me for a long time, waiting to come out? Help?

[khp]

Re: Confused with IVTC

Originally posted by hacker_on_fire
1) does pal = 25fps and ntsc = 29.970fps.

Correct, 23.97 means that you have a 'film' encoded DVD. A DVD player will convert this to 29.97 'on the fly'. The best way to convert such DVDs is to select force film in DVD2AVI. This will decode the vobs at 23.97 instead of 29.97.

Originally posted by hacker_on_fire
2) what is ivtc used for. Also in Doom9's guide it says when you save a dvd2avi project in Gknot to avs IVTC can be activated by choosing it under the Field Operation section & typing a code in the edit mode.

However the edit button cannot be pressed if i select 'Both' under the trim section.

ivtc is used to bring down the frame rate from 29.97 to 23.97.
If you select 'Both' in the trim section, you must open the avs file in at text editor after saving them, in order to edit them.
But if you selected 'force film' in DVD2AVI, this not relevant.

Originally posted by hacker_on_fire
Also i cannot select Inverse Telecine as it does not appear under the field operation.

DVD2AVI does'nt do ivtc.

Originally posted by hacker_on_fire
3) In doom9's guide it says if you perform IVTC, you must change the framerate. How? & Why?

To get Vdub/Nandub to set the correct framerate in the avifile. And to properly calculate the bitsperpixel value.

[hacker_on_fire]

Why would you want to convert the file from 29.97 fps to 23.97 (IVTC)?

I know its not in DVD2AVI, but i cant find it when saving it to avs via Gknot (see pic below)

Also so your saying, after i save it to .avs, you encode it in divX3 using Gknot and then change the framerate? I dont see the point after it is encoded to change it to 29.70 fps

[hacker_on_fire]

dope, heres the attatchments:

one from doom9's guide showing you can select Inverse Telecine

the other a pic when i try save it to avs before encoding it (which shows no option for Inverse Telecine)

[hacker_on_fire]

i cant post 2 pics at one time, so heres them in one file

[khp]

Originally posted by hacker_on_fire
Why would you want to convert the file from 29.97 fps to 23.97 (IVTC)?

Because the 29.97 fps movie was 23.97fps before it was telecined. And ofcause it means that there are 20% less frames in total which ofcause makes the movie more compressable.

I suggest you read this article for a full and indepth explanation of this stuff.

Originally posted by hacker_on_fire
I know its not in DVD2AVI, but i cant find it when saving it to avs via Gknot (see pic below)

OK sorry my mistake, it was propably in a earlier version, maybe the wef removed it because it did'nt work properly.

It's my impression that you need to do a little manual tweaking to get ivtc working in avisynth. There are several different plugins for avisynth that will preform ivtc, but I don't think any of them can give you perfect results, without some tweaking to get the field order right. I think the best place to learn more on this is the avisynth forum at www.doom9.org

But I'am propably not the best person to talk to on this, I live in a pal country, and I have next to no experience with NTSC DVDs.

Originally posted by hacker_on_fire
Also so your saying, after i save it to .avs, you encode it in divX3 using Gknot and then change the framerate? I dont see the point after it is encoded to change it to 29.70 fps

No no, you should not change the framerate after encoding.
If you use forcefilm in DVD2AVI or do ivtc in avisynth you must set the framerate to 23.97 in GordianKnot before encoding.
Otherwise you must select 29.97.

[hacker_on_fire]

ok

the film i'm encoding is film% so i have chosen forced film in dvd2avi. I have chosen 23.97 in Gknot. So it should all be ok.

Also doing ivtc is better. Cos on another film it is 29.970 fps. I should select nothing in dvd2avi. But i should make sure when i load the dvd2avi projetc that Gknot regonises it as 29.970fps. Also when converting it in avisynth (in Gknot) i should do ivtc which will convert it to 23.97fps.

Thanks Alot that just needed to be cleared up.

[khp]

Originally posted by hacker_on_fire
Also doing ivtc is better. Cos on another film it is 29.970 fps. I should select nothing in dvd2avi. But i should make sure when i load the dvd2avi projetc that Gknot regonises it as 29.970fps. Also when converting it in avisynth (in Gknot) i should do ivtc which will convert it to 23.97fps.

As I said, doing ivtc in avisynt is a bit tricky, and I can be of absolutly no help with this.

The other option with 29.97fps DVDs would be to use 'Smart deinterlace' which will remove most of the interlace, but will keep the 29.97fps.

If done correctly ivtc can give you perfect results, but 'smart deinterlace is easier to use. Which metod you choose to use is up to you.

[hacker_on_fire]

thanks a lot

i got a guide from Doom9 showing you how to do ivtc in Gknot

Thanks