[MacDV] Re: 23.98 fps when using Cinematize or DVDxDV

[Aaron]

Dennis sent me the following response off-list, but only because of a misunderstanding that was later clarified. Since the questions raised have not been clarified on the list, I'm going to respond to him here, without deleting anything he wrote. (I've replaced his added right arrows with colons to make it a little easier to follow.)

>Date: Wed, 11 Jan 2006 08:33:15 -0800
>From: "Dennis R. Cohen" <drcohen at mac.com>
>Subject: Re: [MacDV] Re: 23.98 fps when using Cinematize or DVDxDV
>To: Aaron <macuser at aarons.fastmail.fm>
>
>On 1/11/06 at 3:48 AM, Aaron <macuser at aarons.fastmail.fm> transmitted
>the following electronic message:
>
>:>Date: Tue, 10 Jan 2006 16:32:34 -0800
>:>From: "Dennis R. Cohen" <drcohen at mac.com>
>:>To: macdv at listserver.themacintoshguy.com
>:>Subject: [MacDV] Re: 23.98 fps when using Cinematize or DVDxDV
>:>Reply-To: "A place to discuss digital video on Macintosh." <macdv at listserver.themacintoshguy.com>
>:>
>:>On 1/10/06 at 5:46 PM, whoisquilty <whoisquilty at gmail.com> the following
>:>electronic message:
>:>
>:>>Hello -
>:>>
>:> >I keep getting Quicktime files with 23.98 FPS when I convert a DVD to
>:> >MOV with both Cinematize and DVDxDV. I'm trying to create a NTSC file
>:>>from the DVD. The frame is sized to 720x480. But the frame rate always
>:>>comes out to 23.98. I ripped the files using Mac The Ripper 2.6.6.
>:>>
>:>>Any ideas what would cause this?
>:
>:I know nothing about Cinematize or DVDxDV, but I'll make an educated
>:guess about what's going on:
>:
>:If an NTSC DVD was created from a 24 fps movie, it really only
>:contains ~24 fps, along with a code that tells the DVD player to
>:create one extra frame for each four given ones. (Presumably, the DVD
>:player uses 3:2 pulldown to create the extra frames, but I don't
>:suppose it has to!) When a program is converting the DVD's MPEG-2 file
>:to a MOV (or AVI or MPEG-4) file for displaying the movie with a
>:computer, there's really no reason to put in the extra frames, so the
>:file is created with a frame rate of ~24 fps, as in the original
>:movie. (I'm not sure why it would be at 23.976 fps rather than 24 fps,
>:although 23.976 fps is exactly 4/5 of the NTSC frame rate of 29.97
>:fps.)
>:
>:(BTW, I'm curious why one would want to create a MOV file with a frame
>:rate of ~30 fps if there really are only 24 frames per second in the
>:original movie.)
>:
>A standards-compliant DVD requires 29.97 for NTSC and 25 for PAL.
>Although a significant number of players will play NTSC Film (23.976)
>rate content, those are NOT compliant with the DVD standard.

But a MOV file is not used (directly, at least) in a DVD, so how is this relevant?

>:>DVDxDV and Cinematize both default to encoding at what is called "NTSC
>:>Film" rate -- 23.976 fps.
>:
>:Do they do this even when the DVD was made from original NTSC video
>:with ~30 original frames per second? I doubt it, and would have a low
>:opinion of a program that did that, unless it were creating images to
>:be put back on film!
>:
>Yes, they do. 3:2 pulldown is a very common characteristic of many
>streaming and computer-based formats. For example, both DivX and xvid
>default to 23.976, although they will handle other rates. The 29.97 is
>specifically geared to television presentation, which is where DVDs were
>originally meant to be viewed (probably still the primary venue).

My understanding is that 3:2 pulldown is the method by which a ~24 fps film or video is turned into a ~30 fps NTSC video. So why wouldn't a program that was ripping ~30 fps NTSC video for inclusion later in another ~30 fps NTSC video just keep the original frame rate?

>:>If you check the frame rate of the VOB files
>:>ripped by MtR, you'll see they're still at 29.97 fps.
>:
>:According to what indicator?
>:
>Open the VOB in QuickTime Player and look at the "Info" (cmd-I) window.
>It will tell you the frame rate.

Do I need QT Pro and/or the MPEG-2 plug-in to view VOB files with QT Player? Is that why I can't view them now?

>:>DVDxDV refers to
>:>the as "3:2 Pulldown" -- you'll need to use DVDxDV Pro (or some other
>:>converter) to avoid the pulldown implementation.
>:>
>:>--
>:>Dennis R. Cohen
>:
>:If I'm right here, the program's that are creating the  23.98 fps MOV
>:files ARE avoiding "the pulldown implementation", since they aren't
>:creating any extra frames!

Am I right about that?

>:BTW, I found a fairly good explanation of "3:2 Pulldown" at
>:<http://www.dvdfile.com/news/special_report/production_a_z/
>:3_2_pulldown.htm> and intend to reread it when I'm more wide awake.
>:;-)
>:
>
>Enjoy. You can also find a wealth of information at www.videohelp.com.

Yes. It's one of a number of useful sites.

 - Aaron