DVX to DVD

Jason Mann · March 1, 2004

I'm planning to shoot a small project on a friend's DVX-100. I've been reading, and realized I can reverse the 2-3-3-2 pulldown on capture into Final Cut Pro4. I'll be finishing the project on video and using DVD Studio Pro to burn it to DVD.

So should I bother to reverse the pulldown? My understanding is that I'd have to add a pulldown at the end before burning the video to DVD right? Or else my video wouldn't play back on a standard TV? (Or am I way off on that?)

So are there any visual advantages or drawbacks to editing a 23.98fps sequence and then outputting a 29.97fps final project to mpeg2 vs. editing and finishing entirely at 29.97?

And do I get some kind of most-questions-per-post bonus?

Alvin Pingol · March 2, 2004

Reverse pulldown and encode MPEG2 at 23.98fps. Be sure to enable "Enable 3:2-pulldown on playback" (or something similar to that) on the encoder.

The DVD player will automatically add the pulldown for standard NTSC signal.

This is why most DVD players have progressive out for HDTV's, because the 24P MPEG2 stream is progressive and doesn't need to be interlaced for the progressive display. I am 99% sure that DVD players do not do IVTC for the progressive outputs.

Also, encoding at 24fps (a) saves space on the disc since it's 6 less frames per second, and (b) eliminates need for special paramaters needed to encode interlaced signals.

Phil Rhodes · March 2, 2004

Hi,

Well, any MPEG-2 decoder has to be able to handle interlaced streams anyway - it's perfectly allowable to have video-originated DVDs, in fact you are supposed to be able to flick from one format to the other within an MPEG system stream.

I think the whole NTSC progressive encoding thing is just to avoid field duplication.

It also makes region 1 DVDs a lot easier to run on PAL players, since the PAL player can simply run it at 25fps and rescale the frames. Obviously this would only be done under laboratory conditions to test the architecture, since any practical use of the procedure might upset the DVD association. Cough. Cough.

Phil

Alvin Pingol · March 3, 2004

Hi Phil, is MPEG2 encoding (default) field based, or frame based? I originally thought it was the latter, hence the comment about the "special paramaters."

But if it is field based, I could see why one would be able to switch between progressive and interlaced in the same stream (of course, it would still be possible had the stream been encoded frame based, but the compression would struggle with all of the interlace lines).

Phil Rhodes · March 3, 2004

Hi,

Either; you tell the encoder what you want. MPEG-2 encodes each field as a separate image with interlaced source footage. For the same frame rate (compare PAL interlaced video to PAL 25fps film, for example) interlaced material does not compress quite as well, since the 8-pel-square block for a field image is 16 TV lines high. Redundancy between vertically adjacent pels is reduced because of this.

MPEG-1 used a zigzag scanning path to convert the 2-dimensional array of block values into a more easily-encodable one-dimensional string - starting at the top left hand corner of the block and moving in a zigzag pattern. MPEG-2, which supports resolutions sufficient to encode interlacing, has an alternate entropy scanning pattern which provides better performance for interlaced video.

Phil

Alvin Pingol · March 4, 2004

Ah, I see. Thank you very much.

Jason Mann · March 4, 2004

Well, I've started working on this project and I wanted to test how the footage looked by capturing, cutting and outputting the same footage both with the pulldown removed (23.976) and without (29.97).

In Final Cut, unless my eyes deceive me, I see a huge difference. The 23.98 stuff looks much better for motion and the jagged interlace lines are gone. The same is true for the MPEG2 files I output using Compressor (one at 29.97, one at 23.98)

Here's my problem: When I imported both movies to DVD Studio Pro, they both showed up as 29.97 fps. I double checked the actual .m2v files and the progressive one is a true 23.98 file. So did DVDSP convert the frame rate when I imported? Or is it confused? And if so, is it possible to have 24p material on a DVD?

What I thought I understood from before was that the DVD player would add a pulldown. Maybe it's the program that adds it? Help!

(thanks in advance)

Alvin Pingol · March 6, 2004

It is completely possible to have a 24fps stream on disc. I think what you're seeing is that the application is automatically adding the MPEG header data that tells the DVD player to perform pulldown, and therefore shows the file's framerate as what it will appear on an NTSC set (29.97).

If you're still not sure, just burn a DVD with a little bit of both. The worst I think could happen is if the player speeds up the 24fps video to 30, but I doubt it would happen...