Find an explanation: 24 fps on projectors vs on TV/digital devices

[Winbert Hutahaean]

Hi all,

I am curios to know.

In a projector the speed is regulated 18 fps or 24 fps. That is to say if we speed up the projector's motor, therefore, the fps would be above that resulting picture will play faster and sound is pitching.

On the other hand, in the TV world fps is based on the color system, i.e PAL 25 fps and NTSC 30 fps.

Now, if we captured a film from a projector that run on 24 fps using camera that also run at the same 24 fps then when we play the result on NTSC TV is the fps becoming 30 fps (i.e faster) or still 24 fps?

Thanks for the explanation.

[Joerg Polzfusz]

In countries with 50hz, the film’s speed is simply increased to 25fps on TV. In countries with 60Hz, they are using the https://en.m.wikipedia.org/wiki/Three-two_pull_down

[Brian Fretwell]

I wonder if they still use 4/2 pulldown or just telecine to a figital fil at 24fps and use doftware to extract at 30 progressive or 60 interlaced. All standards converted TV shows are done that way when exchanged beteen PAL and NTSC countries now I have been told.

Several recent showings of the film "The Medusa Touch" in the UK have been so converted as to look as it looked as if it had been shot on 50fps video (it is widescreen and from the 1970's so could not have been).

[Alwyn Adkins]

if we captured a film from a projector that run on 24 fps using camera that also run at the same 24 fps then when we play the result on NTSC TV is the fps becoming 30 fps (i.e faster) or still 24 fps?

Disclaimer! My understanding is...

Answer: 24FPS.

I don't think there's such thing as an "NTSC TV" any more. The refresh rate for a TV/monitor might be 60hz (most standard computer monitors have 60hz refresh rate, probably because of the original US standard of 29.97fps) but a TV could have any refresh rate. My LG TV here has a refresh rate of 200hz and many European TVs advertise 100hz. Looking at the US market, there are 120hz refresh rate TVs, so it appears that the old PAL and NTSC regions tailor their refresh rates to the TV transmission standard.

"Pulldown" was/is required to broadcast film material ie 24fps material on the TV network, because the transmitted signal had to be 29.97 frames per second (reason explained in the second paragraph here). Normal pulldown consists of adding fields so that the 24fps film was transformed into 29.97fps for TV transmissions. There's a good description of Pulldown here, including a diagram showing how the added fields are created.

So, for cine, if you shot the 24fps cine at 24fps on your video camera, you'd have pure progressive video and it would play at 24fps on your TV (regardless of refresh rate) ie the "playing speed/motion" would be correct. Same-same 18fps cine; if you were able to capture it with no flickering, it would play at 18fps on your TV. It would be jerkier than 24fps film, as you're not getting as many frames per second to cover the motion, but it would still be correct.

Now, if you were to submit your captured 24fps cine (being now in video format), I assume the broadcast houses would apply Pulldown to make it compatible with the TV transmission standard of 29.97fps. This is why, with an NTSC DVD, you will see 3 clean frames then 2 jaggy frames if you watch it with a computer program that does not remove the pulldown.

So, for todays' world, I don't think there's such a thing as NTSC or PAL. Files will be (if processed properly, of course) simply be a particular FPS and that's it. Phones are a classic example. You can choose 30fps or 60fps as a base, and even then most phones will slow the FPS down to help with low light capture. You then go and play those files on any digital TV or digital screen and you'll get faithful reproduction of the speed without the fps being adjusted.

Another example of the global aspect of fps is Youtube: if you right-click on a video, you'll see the frame rate. I've seen 12, 18, 25, 30, 29.97, 50, 60. They all display nicely on both my TV and my computer monitor.

Lastly, older camcorders are "NTSC" or "PAL". I assume that's to ensure "compatibility" with the local TV standard, including making DVDs where you want to video fps to match the DVD fps so the authoring program doesn't have to convert the fps (similar to 24fps being converted to 29.97). After you've transferred the video, whatever framerate/fps it is, it just becomes another video file that will play correctly on whatever you play it.

[Winbert Hutahaean]

Disclaimer! My understanding is...

Answer: 24FPS.

You may be correct.

So if that is the case, when we speed up the video format during the editing, it will be now shown as 24 fps or now faster?

[Alwyn Adkins]

when we speed up the video format during the editing, it will be now shown as 24 fps or now faster?

By "speed up", do you mean that literally, so it plays faster ie faster movement, or increase the framerate ie the number of frames per second (of playtime)?

I'm not familiar with 24fps cine, but have done a lot of realtime 18fps work. I capture with my camcorder set at 1/50 of a second shutter speed and slow the projector down to 16.67fps to stop flickering. In processing (blended and duplicated frames removal), I end up with my video file at a running speed of 16.67fps, which I speed up to 18fps because that is the correct speed for the film.

In my editor, I would create a timeline of my final desired framerate (say 50fps) and then import my file. The NLE will show the correct length ie playtime, but now there's 50 frames in every second, not 16.67. Now because 16.67 is too slow, I'll then go to the speed control and increase it by 18/16.67=108%. I've now got my video running at the correct play speed of 18.

If you can capture at 24fps, there's nothing to do (obviously exporting at 24fps). If you capture at say 5fps with a frame by frame system, then whatever the original speed was eg 24, that is what the timeline should be set to. Then you should have the correct play speed.

Things get a bit head-spinny when you want to increase the frames in each second to smooth out the motion, but keep it playing at the correct speed (equiv of 18fps).

[Winbert Hutahaean]

By "speed up", do you mean that literally, so it plays faster ie faster movement, or increase the framerate ie the number of frames per second (of playtime)?

I mean the first one, olay faster like 0.5x or 1x.

[Ed Gordon]

...
Now, if we captured a film from a projector that run on 24 fps using camera that also run at the same 24 fps then when we play the result on NTSC TV is the fps becoming 30 fps (i.e faster) or still 24 fps?...

The clearest explanation of what is going on can be found in the link Joerg provided in Post #2 (https://en.m.wikipedia.org/wiki/Three-two_pull_down).

The confusion arises in trying to explain how a 24 FPS movie can be within a 30 FPS video file.

[Joerg Polzfusz]

There are actually four alternative solutions for the „24fps film in 30fps video“:
a) the video simply runs faster than the projected film
b) the video temporarily changes the framerate
c) the computer calculates the six missing frames per second and increases the speed to 30fps (there are several ways to achieve this - from simply blending two neighboring frames to using AI)
d) some film frames are shown more than once (see the „pulldown“-link)

[Ed Gordon]

...I don't think there's such thing as an "NTSC TV" any more.

Why NTSC and PAL Still Matter With HDTV

How digital TV and HDTV are linked to analog television standards

By Robert Silva

Updated on December 2, 2020

Even with the introduction and acceptance of digital TV and HDTV broadcasting and source devices (such as Blu-ray Disc players and media streaming), the old barriers to a universal video standard have not been removed. This article explains why the NTSC and PAL standards still matter.

Frame Rate

Although video is now mostly digital, the frame rate used in analog video systems is incorporated into digital TV and HDTV standards. In video (analog, HD, and 4K Ultra HD), as in film, the images viewed on the screen look like complete frames. However, there are differences in the way frames are transmitted by broadcasters, transferred through streaming or physical media devices, and displayed on a screen.

Lines and Pixels

Video images that are broadcast live or recorded are composed of scan lines or pixel rows. In film, the whole image displays at once. In contrast, the lines or pixel rows in a video image display across the screen, starting at the top of the screen and moving to the bottom. These rows display in either an interlaced or progressive format.


Interlacing or interlaced scan splits the lines into two fields. Odd-numbered lines or pixel rows display first, and even-numbered lines or pixel rows display next, producing a complete frame.

Progressive scan displays rows sequentially instead of transmitting rows as two alternate fields. This means both odd and even-numbered lines or pixel rows display in numerical sequence.

The number of vertical lines or pixel rows dictates the image detail. The more lines in an image, the more detail. The number of lines is fixed within a system.

NTSC and PAL

The two main analog video systems are NTSC and PAL.

NTSC is a 525-line or pixel row, 60 fields with 30 frames-per-second, at 60 Hz system for transmission and display of video images. Each frame is transmitted in two fields of 262 lines or pixel rows that display alternately (interlaced). The two fields are combined, so each frame displays with 525 lines or pixel rows. NTSC is the official analog video standard in the U.S., Canada, Mexico, some parts of Central and South America, Japan, Taiwan, and Korea.

PAL is the dominant format in the world for analog TV broadcasting and analog video display. It's a 625 line or pixel row, 50 fields with 25 frames a second, 50Hz system. Like NTSC, the signal is interlaced into two fields, composed of 312 lines or pixel rows each. Since fewer frames (25) display per second, a slight flicker in the image is sometimes noticeable, like the flicker on projected film. However, PAL has a slightly higher resolution and better color stability than NTSC. Countries with roots in the PAL system include the U.K., Germany, Spain, Portugal, Italy, China, India, Australia, most of Africa, and the Middle East.



DigitalTV/HDTV and NTSC/PAL Frame Rates

Although the increased resolution of digital and high-definition broadcast and video software content standards is a step up when comparing HDTV to analog NTSC and PAL standards, the frame rate is the common foundation of both systems.

In NTSC-based countries, 30 separate frames display every second (one complete frame every 1/30th of a second). In PAL-based countries, 25 separate frames display every second (one complete frame displays every 1/25th of a second). These frames display using either the interlaced scan method (480i or 1080i) or the progressive scan method (480p, 720p, or 1080p).

Where digital and HDTV evolved from NTSC is if frames transmit as an interlaced image (1080i), each frame is composed of two fields, each displays every 60th of a second, and a complete frame displays every 30th of a second, using an NTSC-based 30 frames-per-second frame rate. If the frame is transmitted in the progressive scan format (720p or 1080p), it displays twice every 30th of a second.

PAL-Based Digital TV and HDTV Frame Rate

Where digital and HDTV evolved from PAL is if frames transmit as an interlaced image (1080i), each frame is composed of two fields, each displays every 50th of a second, and a complete frame displays every 25th of a second, using a PAL-based 25 frames-per-second frame rate.

If the frame transmits in the progressive scan format (720p or 1080p), it displays twice every 25th of a second.
The Bottom Line

Digital TV, HDTV, and Ultra HD, although a big leap forward in what you see on a TV or projection screen, still has roots in analog video standards that are more than 65 years old.

As a result, there are differences in digital and HDTV standards in use throughout the world, reinforcing the barrier to a worldwide video standard.

Also, as conversion continues towards digital and HD-only transmission, many still have NTSC and PAL-based video playback devices, such as VCRs, analog camcorders, and non-HDMI equipped DVD players plugged into HDTVs (and 4K Ultra HD TVs).

Even with formats such as Blu-ray, there are cases where the film or main video content may be in HD, and some of the supplementary video features may be in the standard resolution NTSC or PAL formats.

Although 4K content is now widely available via streaming and Ultra HD Blu-ray Disc, 4K TV broadcast standards are in the early stages of implementation. TVs that are 4K-compliant must support analog video formats as long as analog video playback devices are in use.

Eventually, you may no longer use analog video devices, but that day isn't there quite yet.

Source: https://www.lifewire.com/why-ntsc-an...matter-1847856

[Brian Fretwell]

There are actually four alternative solutions for the „24fps film in 30fps video“:
a) the video simply runs faster than the projected film
b) the video temporarily changes the framerate
c) the computer calculates the six missing frames per second and increases the speed to 30fps (there are several ways to achieve this - from simply blending two neighboring frames to using AI)
d) some film frames are shown more than once (see the „pulldown“-link)

I'm sure that the creation of intermediate frames/fields predates "Artificial Intelligence" all "Smooth motion" TVs do this and the Dr Who restoration teeam developed "Vidfire" to make 25fps "Film telerecordings"(kinoscopes to US readers) of 50 field/second TV shows look like the originals as far as motion is concerned. As I said above all TV standards converters use this technology now, not drop or blend frames as in the past.

[Alwyn Adkins]

@Ed, did you read my post? I explained why I thought "NTSC" is no longer relevant.

As for that article, what, actually, was he trying to say? Sure, the technical description of Interlacing, NTSC, PAL are OK, but he fails so say why any of it is significant nor detail any problems with it from the user's POV.

For example:

Although 4K content is now widely available via streaming and Ultra HD Blu-ray Disc, 4K TV broadcast standards are in the early stages of implementation. TVs that are 4K-compliant must support analog video formats as long as analog video playback devices are in use.

Is this some sort of edict to TV manufacturers? What's the point of that statement? The whole article has no actual purpose IMO. It strikes me as just another Internet waffle-on.

The only reason pulldown (24fps to 29.97fps) exists is because of broadcast system requirements. If you're not broadcasting, it's irrelevant.

Back to Winbert's question, we do not need to apply pulldown to our cine videos (or adjust to 25fps). We do not need to do anything apart from create a file that plays at the frame rate of the source ie 18 or 24 fps. These days, regardless of the fps, it will play on any device out there, and it will display at the speed it was created at.

I mean the first one, olay faster like 0.5x or 1x.

Unless you change the play speed in your video editor, it will always display on a TV at the speed of the 24fps cine. Now the TV "might" be inserting frames or doing an internal pulldown, but you won't notice it, just like you don't notice the pulldown when you watch a movie on the TV. Whatever happens, you don't need to adjust the speed of your video file for any particular device.

[Nantawat Kittiwarakul]

Simply put - it's about frame rate conversion.

For 24 to 25 fps, it is usually done by simple speed change. Each individual frame remains untouched, just being played about 4% fast and that's it.
For 24 to 30 (or 29.97/59.94 for that matter) things start to get more complicated. It could be frame repititive (jerky/stutter movement), or frame blending (nasty blurry movement). Some new/better method would already had existed but those 2 old school still exist too - some local channels here still do that afaik.

[Ed Gordon]

@Ed, did you read my post? I explained why I thought "NTSC" is no longer relevant.

As for that article, what, actually, was he trying to say? Sure, the technical description of Interlacing, NTSC, PAL are OK, but he fails so say why any of it is significant nor detail any problems with it from the user's POV.
...

Alwyn, yes I did read your post. Here are reasons for the for the continued relevance of NTSC and PAL, as given in the article, Why NTSC and PAL Still Matter With HDTV.

Firstly, it is essential to understand the basics of NTSC and PAL. NTSC was primarily used in America, Canada, and parts of South America, while PAL was widely used in Europe, Asia, Australia, Middle East, and parts of Africa. Although both of them use different techniques for encoding color, they both use 25 frames per second as their frame rate.

Now, let’s talk about HDTV. HDTV is a digital television broadcasting system that displays video content in high resolution (720p, 1080i, or 1080p). It uses a different technique for encoding color known as YUV or YCbCr. While HDTV is a digital system, it is still compatible with analog systems like NTSC and PAL. Almost all HDTVs come equipped with a built-in ATSC (Advanced Television Systems Committee) tuner for digital television broadcasts and NTSC/PAL tuners for analog broadcasts.

One of the main reasons why NTSC and PAL still matter in the HDTV world is because of backward compatibility. Many older TV shows, movies, and video games are recorded in the NTSC or PAL format. While some of them have been remastered and digitized into HDTV, many of them still remain in their original format. Therefore, HDTVs equipped with NTSC/PAL tuners can still play these older analog recordings without any issues.

Another reason why NTSC and PAL still matter is for international use. While HDTV has provided a unified digital standard for broadcasting, there is still a mixture of standards worldwide. PAL continues to be the prevalent standard in Europe, Asia, and Australia, while NTSC is still used in parts of America, Canada, and some countries in South America. Therefore, HDTVs equipped with both NTSC and PAL tuners can be used worldwide without any compatibility issues.

Lastly, there is a significant cost difference between HDTVs with and without analog tuners. HDTVs equipped with NTSC and PAL tuners are generally less expensive than HDTVs without them. Therefore, for people who don’t want to spend a lot of money on an HDTV, buying one with NTSC and PAL tuners is a practical option.

In conclusion, while NTSC and PAL were developed for analog systems, they still have their significance in the HDTV world. Backward compatibility, international use, and cost-effectiveness are some of the reasons why HDTVs equipped with NTSC and PAL tuners continue to sell well in the market. Therefore, if you’re looking to purchase an HDTV, it is worthwhile to consider one with both digital and analog tuners

Does any of this matter to me? No is does not because I primarily use my TV as a monitor for everything I watch from discs or streaming. I don't watch live TV, but I do record selected broadcast TV via network attached ATSC tuners.

[Alwyn Adkins]

Does any of this matter to me? No is does not because I primarily use my TV as a monitor for everything I watch from discs or streaming.

Ed, that's been my point all along. Your type of TV has no bearing on watching your videos, even your ATSC recordings. Your TV will play anything, of any fps (provided the codec is accepted, of course).

We don't need to change our 24fps cine video to 25, we don't need to change it to 29.97, and we don't need to have a particular type of TV to watch our videos at 24fps.

Can I play an NTSC DVD on my PAL TV? Of course I can, provided my DVD player will play it. Can I play my ripped NTSC DVD MKV file on my PAL TV? Yes, of course I can.

As for your quote in red, again, if you want to watch TV broadcasts, then yes, you need a TV for your region. My original statement did not take into account that someone would be silly enough to buy or take a PAL TV in/to a NTSC country and expect to be able to tune in TV channels. In any case, he reckons TVs with NTSC AND PAL tuners continue to sell well; fair enough if you move around a lot and take your TV with you but otherwise... Our analogue TV system was switched off years ago. And he says HDTVs with PAL and NTSC tuners are cheaper than HDTVs without? Really?