PAL 25P to NTSC 24P conversion - please help

peter-sieben wrote on 3/25/2004, 10:40 AM

Hello,

I've posted my question below as I haven't seen a reply on my question on the support website so far, and I am running out of time. I hope somebody can help me out.

My question relates to the PAL to NTSC conversion. A short movie I made has won a prize at an American film festival. Within one week I fly over from The Netherlands to the States to visit the festival and play the dvd on the big screen. The dvd I made earlier for the festival contains a previous conversion from my PAL footage to NTSC, but I was forced to convert the 25P progressive PAL footage to interlaced NTSC video to make the video not jerkey/stuttering.
(BTW: the footage is widescreen letterboxed video coming from the DVX100 PAL camcorder.)

Now for final playback at the festival I want to obtain a dvd with the best PAL to NTSC conversion I can get with Vegas. I'd like to preserve the progressive footage, so the best what I can think of is convert from 25P PAL to 24P NTSC. I've read the 24P white papers on Vegas and asked a question on Creative Cow forum. But whatever I try, I get stuttering video, visible with motion in the video (I check the MPEG output with Power DVD as I suspect my Windows Media Player playback NTSC material not very accurate). Like it's catching up repeatingly (every second or so).

Is anyone able to provide me a detailed step by step instruction how to do a succesful conversion to 24P NTSC MPEG2? I don't like the duration of the film changed, is that possible with a succesful conversion?
Really hoping to hear from you, many thanks.

Best regards, Peter Sieben

Comments

TVCmike wrote on 3/25/2004, 6:03 PM

Hi Peter,

This is a toughie. Although I have not personally tried this, I would suggest you try two things.

The first is to convert from PAL 25fps to NTSC 29.97fps, then back down to 23.976fps NTSC film using 3:2 pulldown. I honestly don't think you're going to get the quality you want. I'm assuming also that you want "NTSC Film" frame rates of 23.976fps and not true 24fps progressive scan, and I don't know how critical this is. I'd try this with a couple of small sections of your production when you do a render to save yourself the time.

EDIT: I should've been more specific about this, but I believe a standalone MPEG-2 encoder/DVD authoring program (TMPEGenc DVD Author) has the settings that you need to deal with automatic 3:2 pulldown. Theoretically it should be as simple as dropping frames/fields out of the MPEG-2 file that gets converted to . Again, I'm not sure about how acceptable the quality is going to be unless you have your original non-MPEG-2 source, which would be the ideal step-off point.

The other is to bite the bullet and to slow it down, as you suggested. This will affect the audio quality somewhat, and I know that you may have sensitivity in terms of presentation time. However, if it comes to this, you might want to do some creative editing. It's only a 4% difference in the end, though for some productions that's far too much.

As a last resort, maybe you can print it to 16mm film and do a cinetele conversion at a professional outfit. Cheap it is not. Maybe it's your only choice, however.

RBartlett wrote on 3/26/2004, 12:04 AM

You need to reverse what a Hollywood PAL 24p film does when played back on a 25p/50i European deck+TV. Many of course are and have playing times just that bit shorter than their US NTSC counterparts (480p/i).

The film being increased by 4% shouldn't be objectionable when doing so will be the single most important reason why you'll get smooth motion and resolution integrity.

I wouldn't sample up to 59.94i then down to 24p for the earlier reasons.

The thinking is straightforward, the workflow isn't and Vegas doesn't seem to appreciate your plight.

For every second on an NTSC 24p timeline, 24 of the original 25 frames need to be placed down. You can judge on the second or check that the tail end of your movie finishes 4% longer than your PAL timeline.

To watch out for:
Those little notches are your enemy, you don't want to repeat the movie at the end! Be careful when you drag out your clip later in my explanation.

Audio will need a pitch conversion once you've got the above right. 4% upfrequency.

There should be an import or export switch that force things to go right. You are probably fighting Vegas' automatic modes right now.

The video the most obvious workflow would be to save out your movie as PNG frames from another app and import those onto the 24p timeline (with your new stills image length set for 0.041666666666666666666666666666667 secs). Then crop (etc) from 576 to 480 could occur at this point in time. This is also a diabolical workflow.

I would look to the playback rate setting on the PAL AVI you insert. This will then need extending (ctrl drag right) to the Vegas fathomed clip length and the audio upped in frequency. Check the length matches your intended 4% time stretch. A rate change to 0.96 appears to do the job cleanly. The manual for play rate and undersampling has no consideration for frame rate adaptation. Perhaps this will be more accurately described and handled in Vegas5. It is very difficult to even buy a 24p camcorder in PAL countries.

"Match source clip to project frame rate to preserve frame integrity" should be an import option, IMHO.

BJ_M's post here suggests that changing the playrate from 24p to 25p in Vegas can result in an error of .001 (in seconds not frames I think).
here

Spot|DSE wrote on 3/26/2004, 6:39 AM

Try this:
Create PAL Progressive Project in Vegas (new one)
Deinterlace mode to Blend
Change video playback rate to .959 (4% slow)
Drag audio to match length of video
Disable resample for video
Set Best Quality Resample for audio
Right click audio and set to "change Length/preserve pitch" at a quality of Speech 1. You may need to tweak this a little bit depending on source material, but shouldn't have to.
Render at Best setting as a 24P MPEG
You can also do this with an intermediary such as rendering to Uncompressed without effects, dropping that media into the new project, applying FX there. But I think you'll be happy with this, just by changing the project settings, pasting in the old project onto the new project, making these adjustments.

RBartlett wrote on 3/26/2004, 7:24 AM

Is de-interlacing important if the original is 25p?

Or does it provide a certain look, or just a universal technique?

25p is the unwanted NLE mode in Vegas and DVD-Architect.
I blame those DVD Forum/Consortium folks then Sony, in that order!
After this effort, Pesie will re-insist on the length of the movie remaining unchanged....

peter-sieben wrote on 3/27/2004, 6:34 AM

Hi guys,

A lot of information for me to check out and test this weekend. I'll get back to you with my results. Many thanks for all comments made!

Best of wishes,

Peter