Can 720 30p be converted to look like 24p?

[Steve Mullen]

Originally Posted by Barry Green

DVD players can encode two types of footage streams: 24p, or 60i. So if you shoot 30p, you'll be using the 60i file encoding method. And your footage will be displayed as sequential fields, not as whole progressive frames.

1) The 30p will be carried within 60i -- but 30p does not become 60i.

2) It will NOT be displayed as sequential fields because a non-CRT can't display fields!

So the odd and even lines (not fields) will be reassembled back into a frame. The frame will be repeated twice. Just like 25p becomes 50p or 100p for display. No 2:3 pulldown judder at all. Only the natural strobing which is an eye tracking artifact from 24p converted to film, or from 25p, or from 30p.

Film, 24p, and 25p are identical except for the rate the frames are presented. The difference in rates may or may not be significant. But that's an issue of what look you want. And, how much work you want to go to edit your video. For example, some programs will incorporate 60i video -- it's a lot simpler to deinterlace 60i to 30p. Others may need to incorporate film. In which case 24p will be more compatible.

It's still a matter of taste. And, a matter of effort.

[Thomas Smet]

But if the DVD specs do not allow a 30p format will a digital display know how to convert 30p to 60p by duplicating the frames? The question here isn't if 30p in general will display but if 30p on a DVD will work correctly. As far as I know you cannot do a 30p DVD where the flags will be set so the DVD player will add a 2:1 pulldown to duplicate the frames and turn it into a 60p stream. I thought DVD pulldown only worked on a 60i sequence. Again I could be wrong here so hopefully you can clear this up.

If you can do a true repeat flag 30p DVD then what steps should be made in order to do this? I'm sure most people just assume to make a DVD as normal without setting the correct progressive flags. If you make a normal DVD from 30p it in the end wouldn't be much different than a 60i DVD.

Finally do most encoders know to treat 30p video as 30p with the flags? I would think that if this is a valid DVD spec some encoders might be dumbed down since it isn't a very common spec.

[Stephan Ahonen]

30p on a 60i screen should show up as proper 30p without artifacts. When the monitor scans two fields that are really part of the same frame, the effect in the end is that it has really scanned one complete frame because there is no temporal difference between the fields.

[Steve Mullen]

Originally Posted by Thomas Smet

If you make a normal DVD from 30p it in the end wouldn't be much different than a 60i DVD.

It's exactly the same which is why you do not need to do anything special. No worries about encoding. No worries about decoding. (Which dosen't mean that some software can't do 30p.)

But, that does not mean it isn't a 30p DVD! That's because what makes video progressive is the CCD and the process of encoding and the process of display. It is not the means of recording to tape or to DVD.

Specifically, when 30p is ENCODED the progressive video is far more efficiently compressed than interlaced video. That's the virture of 30p vs 60i. That is the DIFFERENCE.

Once encoded, remember that 60i is 30 FRAMES/S exactly as is 30p.

To display, the 30fps is doubled to 60Hz for display.

[Gary Williams]

And by the way I have shot nature footage at 30fps even though it was not 24fps I personal think you can get a film look to it by tweeking the settings in the camera. Some of the footage I have shot at 30fps I personaly think and others have said that looks like film, they actualy thought I shot the footage at 24fps. No one has ever said they thought it looked like video nor do I think 30fps looks like video at all and I also do not think 24fps looks allot better than 30fps. If your not going to convert your project to film I think 30fps is just fine and looks great and is easy to edit. I think that is pretty much what Steve was saying earlier, but if Im wrong Im sure Steve will correct me.

As you can tel I think allot.

[Rob Stiff]

Gary, do you use Final Cut Pro?
Is there a special/optimal formula using Cinema Tools
to convert 30p to 24p and get that further film look?

Does anyone have any results or side by side comparrisons
for the related topic?

[Steve Mullen]

Originally Posted by Gary Williams

f your not going to convert your project to film I think 30fps is just fine and looks great and is easy to edit. I think that is pretty much what Steve was saying earlier, but if Im wrong Im sure Steve will correct me.

You and I are thinking alike on this matter. I've not mentioned this option for several reasons:

1) I expected full 24p support from everyone by NAB.

2) I had not focused on incorporating legacy material into HD.

3) I was expecting a very harsh counter attack.

My version of history is that the desire for 24p came from those who wanted to make films. When Panasonic released the DVX100 it gave folks the chance to shoot real 24p. Filmmakers were overjoyed. The correct mode for going to film was 24PA. But, lots of folks shot 24P and liked the look -- even when they weren't going to film. Suddenly, everybody wanted 24p "video."

Since many of these folks had no technical background, they really never worried about "pulldown." They liked the "look."

During this period the world transitioned from SD to HD and from interlace to progressive displays. I think it's fair to say that many of those buying 24p HD cameras have zero experience with HD and many may not have big-screen HDTVs or huge-screen projectors.

With neither a technical understanding nor experience, they have no choice but to follow the trend and listen to "experts." Shooting 24p is a "faith-based" effort.

I suspect that a large proportion of those shooting 24p would be far better off shooting 30p. This is particularly true if interlaced material needs to be incorporated in your production. Likewise, it you are going to export to HDCAM or DVCPRO HD, your 30p timeline moves to 60i with no issues. Likewise DVDs are easily made.

Folk's should understand that carrying 30p within 60i does NOT change the nature of 30p. The display will make a frame and display it twice -- just like a film projector does. In short, 30p is automatically handled in a 60i world. Just as 25p is handled in a 50i world.

If you use a 1280x720 display, you will have a pixel-for-pixel transfer from the CCD to the display. (This is also true of 24p.)

If there is ANY chance you'll be going to film -- then obviously you should shoot 24p. Or, if you incorporate telecined film (which has 2:3 pulldown) you want to remove the pulldown and place in a 24p timeline.


Lastly, for those too young to remember:

In 1955 the Todd-AO 70mm film system used a 65mm negative running at 30fps. The first major film shot in Todd-AO was Oklahoma!. This print was shown in big theaters in major citites. (The second film was Around the World in Eighty Days.) For general release, they also shot Oklahoma! in 24fps Cinemascope on 35mm stock.

Here's a comment on how 30fps looked: "The difference does not seem great, but the sensitivity of the human eye to flickering declines steeply with frame rate and the small adjustment made the film appear noticeably less flickery, steadier, and smoother than standard 24fps." Does seem anyone thought it looked like "video." :)

Now, can you imagine if the 30fps were compared to 24p WITH pulldown. If real 24fps appears less stready than 30fps, image how much less stready 24fps with judder will look.

But, if you want that judder look, fine. But please don't call it "film look." It is Telecined look." Film does NOT have judder.

Want to see 30p?

The Oklahoma! DVD features a transfer from the 30fps Todd-AO print. The DVD material is decoded as interlaced fields, but unlike video, pairs of fields do belong together. Therefore the DVD player uses 2-2 pulldown where pairs of fields are woven together and each displayed twice (2-2-2-2).

[Gary Williams]

Originally Posted by Rob Stiff

Gary, do you use Final Cut Pro?
Is there a special/optimal formula using Cinema Tools
to convert 30p to 24p and get that further film look?

Does anyone have any results or side by side comparrisons
for the related topic?

Yes Final Cut Pro is my choice for editing but I do not convert to 24p I shoot and edit at 30p State Park and nature videos stuff like that. I like the look I get with the settings I have in my camera for those particular types of shoots, plus you can always make adjustments in post if you want to tweek your look a little more. I dont shoot in 24p and I will probably never use 24p I like a film look or flaver to my video and I think I have achieved that just fine at 30p friends who have seen my work say the same thing. So if I like it and they like it then that soots me just fine. If I ever want to shoot a documantary or something I know I will bump up to film then I always have the option to shoot at 24p but I dont think I need to shoot 24p to get a film flavor to my outdoor work.

[Steve Mullen]

Originally Posted by Rob Stiff

Gary, do you use Final Cut Pro?
Is there a special/optimal formula using Cinema Tools
to convert 30p to 24p and get that further film look?

I think you've got the answer -- there is no need to convert 30p to 24p to have a film look. And, you can't do it even if you wanted to.

[Andrew Young]

There has been a lot said on this topic already, so forgive me for adding a little more hot air to an already wilting subject, but here goes…

For me, 24 & 30 definitely have their aesthetic differences, and each also has their useful applications. On a number of occasions I have shot film at 29.97 because it was going to be telecined and we did not want pulldown artifacts. The transfers looked great. Nobody said the stuff looked like video, but the material did feel more "real" than 24.

Obviously, there are a number of factors both artistic and technical that contribute to a "film look," but on the digital camera side I believe it has at least as much to do with progressive capture as it does frame rate. For me, there's a bigger difference between 60i and 30p than between 24p and 30p. Of course, at very high frame rates progressive capture can start to mimic the temporal sampling of interlaced video. I have seen this when I shot something at 100 to 200 fps (on film) and then sped it up in post to bring it back closer to real time (oops, I shouldn't have over-cranked when that bear was yawning). Believe it or not, the stuff starts to look like video. Very weird, indeed. Obviously, temporal sampling and shutter speed play a huge role in the "look."

Anyway, since the reasons for not shooting 24p have been eloquently stated above, let me stand up for the beleaguered frame rate and state a few reasons why I often choose to shoot 24p (besides the filmout argument):

1) to me 24 fps feels more like an abstraction of reality than 30p or 60i and in that sense it feels more like storytelling than say, reporting. It goes back to the whole temporal sampling thing. Like using diffusion, or playing with shadows, I find temporal under-sampling to be more conducive to story telling. It takes me on a journey more readily than the faster, more reality-like rates.

2) when 24 fps is the time-base of your project you can do more with slow motion. All of a sudden, 30p is a nice mild slowdown and 60p (I'm holding my breath for the HD250) is a really nice 2.5x slowdown. Not everybody cares about this, but if you do, basing your project in 24p really helps.

3) 24p is more bandwidth efficient, offers more bits per frame, takes up less hard drive space, renders in less time, is less processor intensive (yielding better realtime performance) and produces better encodes per unit of storage. - Of course, if you can't edit it without transcoding to another format, you can toss the storage part of this argument out the window:).

4) And of course, there's the filmout argument. No progressive rate other than 24 or 25 should ever be used when going to film. Period.

Yes, 30p may be a better aesthetic or practical choice for many kinds of projects and I do often use it. But 24p is alive and well in my tool kit. Isn't it great to have choices?!

[Steve Mullen]

Originally Posted by Andrew Young

Believe it or not, the stuff starts to look like video. Very weird, indeed. Obviously, temporal sampling and shutter speed play a huge role in the "look."

Wow! When I visit Asia, most of the TVs have refresh rate of 100Hz to avoid flicker. That means each frame is repeated twice. Now this is not the same as shooting at 100fps, but it does mean the eye is being zapped 100 times/second.

I was watching an American detective show uses a lot of handheld camera work. Lot's of camera motion. It looked like it was shot on video!

I too believe that when the frame rate gets to 60fps (60p) [or maybe 50p] we really capture reality. And, I agree that as the rate goes to 24p, we move further away from reality. Clearly, at 24p we reach the ideal point. And, also I agree 30p is more real than 24p.

Buy why? And, is it true for everyone? Can other factors override rate? What happens if we turn on the Motion Filter and add a bit of weird blur?

And, what happens when we go slower than 24p. Do we enter "dream state?" (Yes -- I think.)

I'm curious, what role you think pulldown does. When we go to film we don't oulldown judder, yet when we watch 24p as video we do have "judder." So 24fps film really isn't exactly the same as 24p video.

[Thomas Smet]

24p is also much better for rotoscoping. I for one really hope Hollywood never goes to 60p for this reason alone. It would take 2.5 times longer to rotoscope a 60p source compared to a 24p source.

Also 24p has the advnatge of converting to 25p or 50i very well compared to 30p. This means better global distribution even if it never goes to film but does go straight to DVD.

Converting 30p to 25p would have the same problems as trying to convert 30p to 24p.

24p really is the perfect universal format.

24p to 24p
24p to 60i with pulldown
24p to 60p
24p to 25p with a 4% speed shift
24p to 50p with a 4% speed shift and a 2:2 pulldown.

You may not go to film but why would you want to limit yourself to a U.S/Japan market?

About the only thing you cannot get from 24p is 30p but why would you need to? As much as we might compain about the jutter with 24p and 3:2 pulldown the fact is that most people are used to it. Every Hollywood VHS since the 80's has been done like this. Every Hollywood DVD is like this. Most TV drama work is like this as well along with a lot of the higher end TV commercials. Seeing this jutter is something we have all been used to for a very long time.

I would really like to know what the percentage of stuff shot on 24p really is on Network TV.

[Steve Mullen]

Originally Posted by Thomas Smet

24p is also much better for rotoscoping.

24p really is the perfect universal format.

These are both very good points, but you talk as if someone was attacking 24p. No one is. It's the other way around.

I suspect most of those making money with any low cost HD camcorder are not making product they plan to sell world-wide. Nor will it ever go to film. Nor, will it involve rotoscoping. It's a high-quality version of stuff they have to this point been making in SD -- likely for very local consumption -- often viewed in SD at 60i.

Isn't it obvious that anyone who is shooting product that NEEDS to be 24p will be smart enough to shoot 24p? Give folks some credit.

My point is a simple one -- everything doesn't have to be shot at 24p to get a very high quality look. Do you really want a "Come on Down" commercial to look like Gone With The Wind. Maybe? But, maybe 30p is better. And, 60p might be FAR BETTER. Especially for an off the road SUV commercial.

[Andrew Young]

Originally Posted by Thomas Smet

24p really is the perfect universal format.

This is a really good point that I completely neglected, Thomas. Glad you made it.

I think most people accept that "film look" is catch phrase that means a lot of different things to different people, and that frame rate it but one of several factors contributing to it.

Steve, it sounds like your points are 1) that shooting 24p doesn't always mean watching 24p and 2) that not everyone needs the qualities and advantages that 24p imparts and given that 24p is currently a hassle for HD100 owners and that 30p can look perfectly pleasing, it may be a simpler choice for some users.

I think we all speak to our own set of imaginary readers when we post (at least I do). I guess that's the whole point of forums like this - for people to hear others views and figure out where they fit in.

[Chris Hurd]

Well said, Andy, and many thanks! Much appreciated,