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Old October 22nd, 2006, 01:12 PM   #1
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24P or 30P for DVD?

Is there a benefit to shooting in 24P or 30P for eventual distribution on DVD? Since the DVX100 shoots in 24P, 24Pa & 30P I was wondering which would be the better shooting mode for final use on DVD. Also will the dvd be truly progressive when authored?

I'm using Final Cut Studio 5.1 on an Intel Mac....any workflow suggestions?
(I don't personally need a film look as the videos will be 'Tutorial' DVD's- I just want the best possible image quality.)
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Old October 24th, 2006, 02:44 PM   #2
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Steve,

I am not an expert in this area, but since noone else seems to want to respond, I'll take a shot at it.

I assume from the fact that you consider 30P that you live in the NTSC part of the world, or at least produce for NTSC viewing devices. If you shoot in 24P, you have the option of storing 24 full frames per second on the DVD which is then mapped to a TV's frame rate using what's called a "pulldown" mechanism. Feature film DVDs do that since the source material is 24P. The pulldown may cause a tiny bit of jitter when there is motion (such as panning) in the picture, but it seems to be acceptable to most people. One advantage of storing 24 frames per second is that you need less capacity on the DVD (compared with 30 frames per second), so you can store a longer feature on a DVD. If you were to play back a 24P DVD on a PAL device, it would speed the display up to 25 frames per second, which again seems to be acceptable to viewers in PAL countries. Many filmmakers prefer the "look" that 24 frames per second gives you (more film-like).

If you record (and author the DVD) using 30 progressive frames per second, well, I think it's pretty clear what's going to happen. You have the best possible mapping from video frames to the cycles at which your NTSC device operates.

By the way, to my knowledge there is no such thing as a truely progressive DVD. The image on the DVD is always stored interlaced. Progressive DVD players can read the interlaced picture from a DVD and use the information from two adjacent frames to then output one complete frame and send it to a TV or projector progressively. This deinterlacing can be influenced and assisted by flags that the authoring software adds to the DVD. That's what they do with feature films (filmed in 24P) when they are transferred to a DVD, they store each original frame as two interlaced halfs of a frame on the DVD, and a progressive DVD player (i.e., one that's capabable of deinterlacing these two halfs) simply puts them back together the way they were at the beginning. Note that deinterlacers work very differently when deinterlacing DVDs that were authored from interlaced video material.

I believe that's it in a nutshell. Now it's time for the real experts to tell me what I got right and what I got wrong! :)

Hope this helps you!

- Martin
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Old October 24th, 2006, 05:35 PM   #3
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If the viewer has a progressive-capable DVD player, they will be able to watch without pull-down. Progressive-encoded DVDs simply have a switch that indicate which frames should be interpolated, and progressive-capable players ignore them to reveal the progressive footage.

It is better to encode in 24P than 60i for the simple reason that it takes up less space.
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Old October 24th, 2006, 06:29 PM   #4
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you need to decide what to shoot on based on the project. what are you shooting and would the respective looks of 24 or 30p be best? Both will go to DVD fine, but as already said, 24p takes up less space.
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Old October 25th, 2006, 07:47 AM   #5
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Quote:
Originally Posted by Martin Pauly
By the way, to my knowledge there is no such thing as a truely progressive DVD.
As far as I know, that's incorrect.

Unless I've been lied to, most (if not all) "Hollywood" DVDs are 24p, and the extra baggage needed to view on non-progressive monitors is done by the player itself.
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Old October 25th, 2006, 02:56 PM   #6
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Originally Posted by Emre Safak
If the viewer has a progressive-capable DVD player, they will be able to watch without pull-down.
And how exactly do they map the 24 original film frames to the 60 NTSC frames each second without using pull-down? Here is some suggested reading on this topic:

http://www.avdeals.ca/classroom/Proscanexplained.htm

According to this article (and my math), even with a progressive scan DVD player and a display device capable of displaying 60 progressive frames a second, the 3:2 pull-down is necessary. The advantage compared with non-progressive players is that no full frame sent to the TV by the progressive DVD player ever consists of two fields that are from two different frames of the original 24p film.

Quote:
Originally Posted by Daniel J. Wojcik
Unless I've been lied to, most (if not all) "Hollywood" DVDs are 24p, and the extra baggage needed to view on non-progressive monitors is done by the player itself
Daniel, if you take a look at the same article I referenced above, you'll find: "But sources which are truly progressive in nature are hard to come by right now. Movies on DVD are almost always decoded as interlaced fields yet all of the film's original frames are there, just broken up."

Another reference: http://www.allformp3.com/dvd-faqs/140.htm
A quote from there: "There's enormous confusion about whether DVD video is progressive or interlaced. Here's the one true answer: Progressive-source video (such as from film) is usually encoded on DVD as interlaced field pairs that can be reinterleaved by a progressive player to recreate the original progressive video."

- Martin
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Old October 25th, 2006, 03:36 PM   #7
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technical details aside, i like 30P for DVD output...basically, it handles motion more smoothly than 24P, which makes it a bit easier to work with, from the shooter's perspective. 30P is less film-like in its texture than 24P but more than 60i. it is a bit between the two. it's my favorite option of the three (on the XL2). pans can look jittery in 24p, and 60i is too video-ish. 30p is the good compromise. you should add some motion to 24p footage and see if it jitters or not or if that jitter bothers you....like someone mentioned, it can be a personal taste issue.
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Old October 25th, 2006, 03:54 PM   #8
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Quote:
Originally Posted by Martin Pauly
And how exactly do they map the 24 original film frames to the 60 NTSC frames each second without using pull-down?
They don't have to do any such thing, the viewer's DVD player adds the pulldown. Didn't you explain this yourself? Am I missing something?

It is entirely possible, and it is often done, to encode an MPEG-2 file at 24 progressive frames per second that will play back on a regular interlaced DVD player--because the player adds the pulldown upon playback if operating in interlaced mode. Since that's the case, why wouldn't a progressive player be able to play back the progressive MPEG on the disc simply by not adding the pulldown at playback?

If you doubt this is the case, Martin, then try encoding an MPEG-2 file using your authoring software's 24p preset(s), check it with something like GSpot (which will analyze the video and tell you it is 24 frames progressive), and then burn it to a disc and watch it play back just fine on an NTSC TV. :)

Quote:
Originally Posted by Meryem Ersoz
pans can look jittery in 24p
24p shouldn't look too "jittery" or "stuttery" (or whatever you want to call it) with faster motion if a 1/48 shutter speed is used. Film has been shot at 24 frames per second with a 180-degree shutter angle (ergo at a shutter speed of 1/48) since the "talkies" arrived, and no one ever complains about it looking jittery. I think that when people complain about strobeyness in 24p footage, 99% of the time they're talking about footage shot with faster shutter speeds--like the 1/60 which is common for interlaced video--and are not taking the shutter speed into account as a massive part of the motion equation.

If you still think your pans look jittery in 24p, then pan more slowly. Problem solved. :)

Also, for those interested: as noted above, 24p carries less image data with it (since there are fewer pictures per second) than 60i, so you can encode at a higher bitrate or fit more video onto a disc than would be possible with 60i. What hasn't been mentioned so far is that there are no such advantages with 30p. Players can't reconstruct a true 30p sequence; instead, they read 30p as regular 60i--with a single progressive frame being interlaced with itself, so that the same image serves as 2 fields. To DVD encoding software, 30p as recorded by NTSC cameras just looks like regular old 60i, and is treated exactly as if it were just that. Just thought I'd point that out in case it wasn't obvious.
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Old October 25th, 2006, 05:31 PM   #9
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"pan more slowly" is over-simplifying the issue. i think it depends on your application. if you're trying to shoot a kayaker running a slalom course, pan more slowly is not a solution....that's often the kind of thing i shoot. if you're going to film, then by all means, use 24p, if that's what your lab prefers. or if you're shooting a narrative with a bunch of dialogue, use 24p....but 24p is not always the best choice, and it's certainly not always the best choice for filming motion oriented subjects for DVD delivery....

these are all good tools to have, and it's a matter of picking the right one for the right job.
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Old October 25th, 2006, 06:06 PM   #10
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Quote:
Originally Posted by Meryem Ersoz
"pan more slowly" is over-simplifying the issue. i think it depends on your application. if you're trying to shoot a kayaker running a slalom course, pan more slowly is not a solution....that's often the kind of thing i shoot. if you're going to film, then by all means, use 24p, if that's what your lab prefers. or if you're shooting a narrative with a bunch of dialogue, use 24p....but 24p is not always the best choice, and it's certainly not always the best choice for filming motion oriented subjects for DVD delivery....

these are all good tools to have, and it's a matter of picking the right one for the right job.
Well, yes... 24p is usually best for narrative or other "cinematic" work, and 60i or 30p is usually best for "reality" footage like sports and so on. (24fps was fine for those things until we all got used to seeing 60i, but that's another can of worms.)

But that wasn't the point being discussed. :) You said in general terms that you felt that 24p is too jittery, and didn't make any allowances for different styles of shooting in any of what you said. My point was simply that too many of the people who argue that 24p is "jittery" also happen not to understand that 1/48 shutter speed is a big part of the effect. 24p with a 1/48 shutter will actually give you much smoother motion than many people seem to realize. I didn't mean to imply that you didn't realize this, just that it seems to be a common thing.
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Old October 25th, 2006, 06:15 PM   #11
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My research has me finding the 30P setting most suitable for my intentions. I do need smooth movements and prefer the higher resolution and sharpness 30P affords and having it end up as a progressive DVD is a plus....

...I plan on producing instructional DVD's on how to airbrush using my sponsors products (Alsa Corp. Paint) and the custom paint community is screaming for such instructional DVD's. I have a rather unique "photorealistic" style of painting allot of custom painters find difficult to emulate.

Thanks for the posts everyone- much appreciated.

(someday I hope to get back to my nature videography- but work comes first)
~~ In case anyone wants to see what sort of work I do- have a peek at www.stevenunez.com ~~
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Old October 25th, 2006, 06:25 PM   #12
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Originally Posted by Steve Nunez
I ... prefer the higher resolution and sharpness 30P affords and having it end up as a progressive DVD is a plus....
What I'm about to say is not about trying to convince you to shoot 24p, it's just a "for the record" kind of thing: 30p will give you no more resolution or sharpness than 24p. I'm a little puzzled by your statement that such would be the case.

You also mention that a progressive DVD would be a plus. See my earlier comments on 30p and DVD encoding. 30p on a DVD will look progressive in every way on an interlaced display, but is not truly progressive at the point of DVD encoding or playback since the encoder you use and DVD players will treat it as if it is regular 60i. You may in fact still see interlace "jaggies" with 30p (when shot on an NTSC camera) when viewed on a progressive display. It's a small, semantic difference in some ways, but one that is a valuable thing to understand if you really want to know what's going on "under the hood," or if you're hoping to preserve extra encoding bandwidth as you can with 24p--30p just doesn't work the same way.
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Old October 25th, 2006, 11:51 PM   #13
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I meant more resolution as when compared to 60i interlaced mode which only shows 1/2 the image at any given moment.

As for the 30P not being truly progressive on an NTSC monitor- I wasn't aware of that- I sorta recall a page somewhere where a guy posted both 24p & 30p can be made into true progressive scan dvd's....I'll have to look into this a bit further.

Thanks for the comments thusfar- much appreciated.
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Old October 26th, 2006, 10:07 AM   #14
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one advantage to shooting your own work is that it's easy to run a quick test comparing all three choices on an identical work of art in a controlled lighting environment. i shot a documentary on an artist, and i shot the artist working in 60i, because i wanted that extra resolution (he worked in sand, and i wanted to be able to see the specific granules), and the rest of it, i shot in 30p (talking heads, interviews, etc.). these mixed easily in the same 29.97 timeline. when i saw it projected on the big screen, i preferred the 30p look overall--too much shiny video taking up too much screen real estate. and the blow-up challenges the resolution anyway. but when i watch it on DVD on a TV or small screen, i think the blending works well. you might want to test how your camera and your artwork inter-play with each other a bit before you decide.

the FX-1 would be perfect for this, but you can't have it back! the magic bullet for the FX-1 is the 1/2 schneider black frost filter, which warms the image, gives nice skin detail but maintains the hi-rez.....
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Old October 26th, 2006, 01:27 PM   #15
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Originally Posted by Steve Nunez
I meant more resolution as when compared to 60i interlaced mode which only shows 1/2 the image at any given moment.
Spatial resolution is the same either way, because no one is looking at the screen for only 1/60 of a second. :) 60i's only spatial resolution disadvantage is that you lose a lot of res when deinterlacing (if desired and/or necessary). 60i's temporal resolution is actually twice that of 30p.

Quote:
Originally Posted by Steve Nunez
As for the 30P not being truly progressive on an NTSC monitor- I wasn't aware of that- I sorta recall a page somewhere where a guy posted both 24p & 30p can be made into true progressive scan dvd's....I'll have to look into this a bit further.
Well, nothing is truly progressive on an NTSC monitor, because NTSC is interlaced by definition; in order for anything to play in NTSC, some kind of interlacing is necessary--either directly applied to the footage (as with 30p), or in a "meta" sense in the form of pulldown (as with 24p).

DVD players insert pulldown (or "pullup") in order to play a 24p disc, because it is necessary to do so in order to fit 24 frames into 60 interlaced fields. But 30 progressive frames fits evenly into 60i, so no pulldown is necessary. Because of that, cameras record 30p to tape in a 60i stream, and there's no easy way to extract those frames and work in a 30p timeline, whereas you can do just that when editing 24p. Furthermore, DVD authoring software typically offers no project templates for 30p, because the standard 30p workflow is built around 30p being embedded in a 60i stream. While it is theoretically possible to author a 30p DVD, of course, the usual post-production software routes do not offer the option to export 30p in any way other than as a 60i stream. As far as I know, at least. I am not 100% sure, but I suspect that a true 30p disc would not play back on an NTSC DVD player. The players are designed to add pulldown to 24p, because that's the way Hollywood does it. But as far as I know, interlaced players are not equipped to play 30p back as NTSC-compatible video.

For the most part, the difference is purely academic anyway, because the results look pretty much exactly the same either way. The main difference is that 30p pretty much has to be encoded to MPEG-2 as 60i, and thus requires more encoding bandwidth than honest-to-god 30p would.

At the end of the day, none of this is as important as what looks best to you, or what works best for the project. But it's helpful to understand how all of these frame rate things work, because it allows you to make more informed decisions.
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