PAL Avi to NTSC DVD works, but changes film length

[rkorkie]

I have been combing the forum for the last few days, and have had all the answers I need, except the one I'm about to ask.

I have an AVI which I wanted to convert to DVD, so I followed doom9's conversion guide. Everything went well until I authored the DVD to find that the audio gradually got more and more out of sync. Further research led me to find that I was dealing with PAL to NTSC in some respect.

I loaded the original AVI into VirtualDub to find it was 25fps. So, I researched Avisynth scripts, and used the following:

AviSource("film.avi", false) #added false cause avi has audio
AssumeFPS(23.976)
BicubicResize(720,272) #avi is 2.85:1, doesn't need PAL resizing.
AddBorders(0,104,0,104)
ConvertToYUY2(interlaced=true)

Thinking that this script would convert from PAL to NTSC and preserve the same movie length and quality, I encoded it and ran 2:3 pulldown on it. However, the movie went from the original 2h11min to 2h16min.

This is fine, because I was able to convert the audio using BeSweet using the PAL->NTSC preset, and the time lengths finally matched up and authored it with Scenarist and everything was in perfect sync.

However, during all this time, I haven't been able to figure out the real problem. Is there any way by changing the original AVI framerate in VirtualDub or using Avisynth scripts to not only convert from PAL to NTSC, but also to preserve the original movie length? Or is this simply a matter of math, and anything going from 25fps to 23.976fps will be proportionately longer in length?

Any help on this would be appreciated!! Thanx.

Ryan

[Zhnujm]

Theres nothing wrong with your method, its the normal way to do it, PAL movies are played a bit faster.
In fact, if your file is a cinema movie you have now the original playing time (2:16).
There are other ways to do this (framerate conversion) but this will be much worse than a simple slowdown/speedup.

Also this will only work with a progressive source, not with a truely interlaced PAL source.

[Siku]

Hi

The movie lenght changes because your FPS (Frames Per Second) chances. For example if your clip has 1500 frames and your FPS is 23.976 the lenght of your clip will be (1500/23.976=) 62.56 seconds. And if your FPS is 25.000 the lenght will be (1500/25.000=) 60 seconds. So that's why your movie has the lenght you described.

There is alternative ways to change the FPS, see this this (http://www.avisynth.org/index.php?page=FPS).

I hope my explanation is correct, if it's not, feel free to correct it! :)

Regards,
Siku

[rkorkie]

Thanx for the explanation guys. I thought that was the case. I'm just a perfectionist, so I try not to do things half-assed just to get it to work. I like to know exactly why something behaves a certain way, cause computers are 0's and 1's, so everything is black and white...not maybes.

Just fyi, and not to break forum rule #6, but I happen to be evaluating a pre-release copy of a certain movie with Neo, which I do have on pre-order, so I don't feel like I would be breaking any major laws!! ;-) Anyhow, just seemed strange that the AVI file was 25fps...I'm wondering if the original source was NTSC or not. I took a look at most other AVI's I have, and they are all pretty much 29.97. Oh well...

[Wilbert]

So, why are you breaking it then? Thread closed.