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

[Thomas Smet]

Besides film doesn't 24p have an advantage over 30p on DVD's as well?

I thought 30p DVD's only worked as 30p put into a 60i mpeg2 stream. When this is watched on a progressive display the 30p frames would get bob and weave thinking that it was 60i. This means highly reduced vertical resolution with no framerate gain since there is no second field of data.

I thought progressive DVD players only looked for the 24p. I thought I read somewhere that 30p with true progressive frames and progressive flags wasn't in the DVD spec. I could be wrong here though. Maybe I should try burning a 30p DVD tonight and see what happens.

[David Parks]

Therefore, you should be able to get a TRUE film look using 30p. In fact, a more true film look than shooting 24p!

Unless you really go to film, shooting 30p -- with each frame presented twice upon video viewing -- is very much like film where each frame is flashed twice by the spinning shutter. You get the SAME strobing artifacts.

You get nearly the same shutter speed and nearly the same frame rate.

That's the virtue of 30p -- plus no editing issues.

In fact, a lot of 16mm/35mm projects that I've been involved with was shot with a cinemacontroller running at 29.97 and transferred via Rank or Datacine to DigiBeta
(w DiaVinci Color Correction) at 29.97, so we would get a sharper look. Like stated earlier it is more expensive)

I've noticed that 24p looks softer than 30p.

But so far as going 30p back to 24p, I don't know if a transfer house can do that with progressive yet.

[Barry Green]

Several claims made in this thread are ... well... just not right.

First: 30p doesn't look more like 24fps film than 24p does. The assertion is simply nonsense. 30P never looks like film. It looks like a halfway hybrid of film/video. 30P may look like film that's been shot at 30fps, but that's a very rare case, as Charles pointed out.

Second, yes 24p DVDs have a definite advantage over 30p on DVD. DVD players have been designed from the beginning to work with 24p footage; it's one of the requirements Hollywood insisted on. So you can author a 24P DVD from 24P footage and it will play back at 24fps on a progressive monitor, or with 2:3 pulldown on an interlaced monitor. You can store more footage in 24p on a DVD, or use lower compression to get better quality out of the same amount of runtime. And the compression is cleaner and more efficient than the 60i compression.

Third, the assertion that you never see 24p outside of a movie theater is just wrong. If you've ever watched a DVD on your computer, or played a DVD on a progressive DVD player to a plasma, LCD, or other progressive monitor, or watched a movie trailer on the web, or... well, basically watched on anything other than a CRT, you've watched 24fps with no pulldown and no interlacing.

Fourth, we're extraordinarily accustomed to watching 24fps footage with pulldown. Every network drama, every sitcom, every movie-on-TV, every VHS hollywood movie, every DVD we've ever watched on a regular CRT television for the last 50 years has been 24fps with 2:3 pulldown. And that's the look that 24p cameras deliver. To argue that 30p footage looks more like film on our televisions than what actual film looks like on our televisions is... well, it's just wrong.

24P gives you options. It looks like film. It can be authored to a 24P DVD. It can be transferred to film. It can be easily converted to PAL 25P. It's the "universal" format.

30P is basically an orphan format. Makes for a lousy conversion to PAL, can't be converted to film well at all, and looks like a hybrid cross between film and video, offering the worst of both worlds. It's a choice, it's an option, but there's a reason that it's a rarely-selected choice.

If you want your footage to look like film, shoot 24p (or, in EU, 25p).

30P is best reserved for either a) a mild overcranked slow-mo look when inserted into a 24p project, or b) a smoother-motion alternative to the strobier 24p, when shooting events that you don't want to have look like film.

[Stephan Ahonen]

Even if you are watching on a progressive scan monitor, you're not necessarily avoiding pulldown. Watching movie trailers on the internet, for example, unless your computer monitor is scanning at 72 or 96 Hz, there is definite pulldown, and possibly image tearing (when a frame advances in the middle of a scan) occurring.

[Rob Stiff]

Barry, thank you for taking the time to make things clear.
I think it is safe to say most people who bought
the HD-100U cameras are due its true
720 24p ability.

30p looks like home video compared to 24p.

I use FCP and have to do some twisted things
to edit the 24p footage. Apple & JVC have taken
so long to provide any real turnkey solutions.

NAB came and went, and nothing immediate....

Just trying to learn more "workarounds" to get
the best results until FCP supports our 24p format...

[Barry Green]

Originally Posted by Stephan Ahonen

Even if you are watching on a progressive scan monitor, you're not necessarily avoiding pulldown. Watching movie trailers on the internet, for example, unless your computer monitor is scanning at 72 or 96 Hz, there is definite pulldown, and possibly image tearing (when a frame advances in the middle of a scan) occurring.

Well, image tearing, yes, but pulldown?

You're seeing 24 frames played per second. There's nothing added to round out that sequence (which is what pulldown is). 24 times per second you'll see a different frame displayed.

I mean, in the movie theater you also see a bit of an effect from the fact that the shutter closes, and not instantaneously -- it's a rotary disc, so it closes from the top to the bottom over the course of typically 1/48 or 1/72 of a second. But you're still seeing only 24 images per second. And that's what the computer monitor is giving you -- 24 discrete images per second, equally spaced in time at 24hz intervals.

Pulldown is a way to round out the sequence because 24 frames doesn't divide evenly into 60 fields on TV.

It would be correct to say that you're not seeing 24 full frames displayed for 1/24th of a second artifact-free and flicker-free, even in the movie theater, due to the way TV screens draw and due to the way film shutters close. But pulldown is a separate concept; pulldown is how the JVC embeds 24fps within its 60fps data stream on the analog outputs -- one duplicated frame out of each group of four. But that's not what happens when you watch a 24p DVD or 24fps film projected.

[Brian Luce]

I had the impression the HD100 records a true 24fps, something like the hvx's 24pN. But now you're saying it capturing 30 and flagging six frames?

[Barry Green]

No, the HD100 scans a true 24fps signal. But HDV 720p doesn't provide a recording format for 24fps, its only options are 25, 30, 50 or 60. So in 25p mode, yes it's just 25 frames and only those 25 frames (AFAIK). But in 24p mode, it's 24 frames carried within a 60p data stream. Sort of like the HVX does in its "over 60" mode, but much more efficiently, because the "pulldown" frames aren't actual recorded frames that take up bandwidth; instead they're just "repeat flags".

So almost all the available bandwidth is used to record only the 24 frames, but it's not transporting a 24p stream, it's a 60p stream. Some editors recognize the files as a 24p stream and know to ignore the pulldown/repeat flags, other editors or programs recognize it as a 60p data stream.

For all practical purposes it is indeed using its bandwidth to only record the 24 frames, as the pulldown flags don't really change anything.

[Ben Brainerd]

Originally Posted by Barry Green

Second, yes 24p DVDs have a definite advantage over 30p on DVD. DVD players have been designed from the beginning to work with 24p footage; it's one of the requirements Hollywood insisted on.

At the risk of Thread-jacking, I must admit that I'm confused here. I may have missed something, but the way I'm reading the 24p/30p DVD thing is that a progressive player, hooked to a plasma/LCD/other progressive display will display 24p. But 30p footage HAS to be converted to 60i? Or am I just completely off base here?

I know there are numerous displays out there that can handle 30p, but it seems to be a bit of a moot point if the only way to actually get 30p into them is via the camera or a computer.

[Stephan Ahonen]

Originally Posted by Barry Green

Well, image tearing, yes, but pulldown?

You're seeing 24 frames played per second.

If you watch a film broadcast over NTSC you're seeing 24 frames played per second as well. It's just pulled down. Your monitor, regardless of whether it's CRT, LCD, Plasma, whatever, scans at a fixed rate per second just like a regular television. Unless your monitor is refreshing at an exact multiple of the source framerate (i.e. 72 Hz for 24p content), your video card has to either pull it down or simply put up a new frame every time it gets one regardless of where the monitor is in its refresh cycle, resulting in tearing.

You can set the refresh rate of most CRT monitors to avoid this. I'm not sure about LCDs, having never owned one (I don't trust their color). Monitors made for modern home theater setups can generally change their scan rate depending on what kind of content they're trying to display.

[Steve Mullen]

Originally Posted by Ben Brainerd

But 30p footage HAS to be converted to 60i? Or am I just completely off base here?

Non-CRT displays are 60p. 24p must have 2:3 pulldown added to get to 60p. 30p must have 1:2 pulldown added to get to 60p.

[Steve Mullen]

Originally Posted by Stephan Ahonen

Monitors made for modern home theater setups can generally change their scan rate depending on what kind of content they're trying to display.

High-rez. computer LCDs, in fact all LCDs, plus plasmas and DLP run at 60p.

Which means only a few LCD computer monitors and CRT monitors run faster than 60Hz. Everything is converted to 60Hz.

The ideal would be 72Hz since 24Hz could simply be repeated 3X. But, technology isn't quite able to do 72Hz yet at a reasonable price.

Interesting. Neither Sony or Panasonic even make CRT monitors for video so the color issues are really gone. Black level is the remaining problem.

[Barry Green]

Originally Posted by Ben Brainerd

But 30p footage HAS to be converted to 60i? Or am I just completely off base here?

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.

[Steve Benner]

Originally Posted by Steve Mullen

High-rez. computer LCDs, in fact all LCDs, plus plasmas and DLP run at 60p.

Which means only a few LCD computer monitors and CRT monitors run faster than 60Hz. Everything is converted to 60Hz.

The ideal would be 72Hz since 24Hz could simply be repeated 3X. But, technology isn't quite able to do 72Hz yet at a reasonable price.

Interesting. Neither Sony or Panasonic even make CRT monitors for video so the color issues are really gone. Black level is the remaining problem.

So even when I watch a 24P Quicktime file, a pulldown is being used?

[Brian Luce]

I'm no longer certain after reading this when one should employ 24p. Is it for filmout only?