Do any movies use true 24p?

[Zombienietzsche]

Originally Posted by 4K2K

But surely a "progressive-scan" "120Hz" LCD HDTV doesn't use fields for output - it uses frames (and any interlaced footage on input will be converted by the TV to progressive before display, so again it won't output fields).

I still don't understand (and 1 field = half a frame).

Does a "120Hz" LCD HDTV output a 23.976Hz source from a Blu-ray player at 119.88Hz (23.976*5), and does it output a 24.000Hz source from a Blu-ray player at 120.000Hz? Or does it output everything at one rate - eg. 119.88Hz and for the 24.000Hz source omit an output frame every so often (ie. not do a full 5:5 pull-down)?

That is dependent on disc authoring, and whether or not you are being given the correct info. As the master provided can vary and use either 23.976 or 24.
SOME sets can do a 5-5 pulldown on 23.976 just like 24p. older sets do a 6-4 pull down there was a thread here for the longest time with lists of sets capable of displaying it properly.

https://forum.blu-ray.com/display-th...rame-rate.html

In short maybe, it depends on your tv, the disc, and the master used for authoring! ITS A PAIN you should read this thread as it is enlightening

http://www.avsforum.com/avs-vb/showt...1187090&page=4

Also if I made a mistake in regards to the use of frame v field, sorry its a bad habit.

But still for U.S. purposes 23.976 = 24

EDIT If anyone has concrete proof for a definitive answer I would like to see it.

[ghostdrknss74]

wow didnt know that, ill check on my list of blu rays which has the 24p

[Alex Pallas]

thanks for all the replies. i suppose it isnt terribly important like many of you have pointed out. i just like round numbers and would prefer the original framerate even if its not noticeable... i dont see why we should keep around the weird analog 23.97 frame rate when it could just be 24fps :S

[lagunaseca]

There is a lot of wrong info in this thread. One guy is talking about lossless audio when 24fps is about video only, and another guy is saying 23.976=24 and it's all "A/C oscilliation". Not sure what that means.

23.976fps is not the same as 24fps. 35mm films are 24fps, and in the old days black & white was broadcast at 24fps. When color TV came out they needed to be able to broadcast to support both color and B&W TVs. That's when they came up with the 23.976fps hack. Even I don't understand is completely but please see this Reddit discusstion:

https://www.reddit.com/r/explainlike...c6&sh=d7e5d8d9

Also see this YouTube video explaining it:

The History of Frame Rate for Film - YouTube

Ideally you want to have a round fps number to reduce complexity in processing the data (which saves time and money). Working with fractions is more time consuming than working with whole numbers. See FPUs (https://en.wikipedia.org/wiki/Floating-point_unit)

Studios need to stop authoring blurays at 23.976fps. So far all of the Bollywood blurays I've seen are 24fps and I haven't see any issues playing them.

In regards to audio, the reason why DVD's audio tracks are 48,000hz instead of 44,1000khz is because 48khz is evenly divisible by 24fps. 44.1khz was good for audio CDs, but when you have audio AND video you need even divisible round numbers to make it easier to process audio & video together. But the video on DVDs was still 23.976 becuase it was outputting analog video. With digital video there is no reason to have a fractional frame rate.

[ZoetMB]

Originally Posted by lagunaseca

There is a lot of wrong info in this thread. One guy is talking about lossless audio when 24fps is about video only, and another guy is saying 23.976=24 and it's all "A/C oscilliation". Not sure what that means.

23.976fps is not the same as 24fps. 35mm films are 24fps, and in the old days black & white was broadcast at 24fps. When color TV came out they needed to be able to broadcast to support both color and B&W TVs. That's when they came up with the 23.976fps hack. Even I don't understand is completely but please see this Reddit discusstion:

https://www.reddit.com/r/explainlike...c6&sh=d7e5d8d9

Also see this YouTube video explaining it: The History of Frame Rate for Film - YouTube

Ideally you want to have a round fps number to reduce complexity in processing the data (which saves time and money). Working with fractions is more time consuming than working with whole numbers. See FPUs (https://en.wikipedia.org/wiki/Floating-point_unit)

Studios need to stop authoring blurays at 23.976fps. So far all of the Bollywood blurays I've seen are 24fps and I haven't see any issues playing them.

In regards to audio, the reason why DVD's audio tracks are 48,000hz instead of 44,1000khz is because 48khz is evenly divisible by 24fps. 44.1khz was good for audio CDs, but when you have audio AND video you need even divisible round numbers to make it easier to process audio & video together. But the video on DVDs was still 23.976 becuase it was outputting analog video. With digital video there is no reason to have a fractional frame rate.

Sorry, there's a lot wrong in your post. Analog TV did not broadcast at 24 or 23.997. It broadcast at 30fps originally and had to switch to 29.997 when color came in. But all this applies only to analog TV. 24 fps movies were converted using what's called a 3:2 pulldown to 30fps (or 29.997 once color came in) for broadcast. You can lookup what that means..too many details to note here. TV shows recorded on video were recorded at 30fps (or 29.997).

The reason why color analog TV had to change the 30 fps rate is because the 3.58MHZ color subcarrier would absorb common phase noise from the harmonics of the line scan frequency. So they adjusted everything else except the audio and chroma subcarriers, including the frame rate. So they took the 30 Hz frame rate (not 24) and divided it by 1.001 to get 29.97.

But then they also had to adjust the SMPTE Time Code because at 30fps, an hour of timecode was longer than the wall-clock time by 3.59 seconds. That would lead to an 86.16 second error per day, something unacceptable for television scheduling, especially when it became automated.

So SMPTE "Drop-Frame" Timecode drops frame numbers 0 and 1 of the 1st second of every minute, except when the number of minutes is divisible by 10. Note that the video frames aren't actually dropped, just the timecode frames are dropped.

But drop-frame isn't actually used much anymore. I know this because I was responsible for the development of an application used by the industry that incorporated asset metadata, including SMPTE timecode. When we asked all of the clients whether we needed to support drop-frame, everyone said no (but I left it in anyway as an option).

As for audio, I can't say I know this with 100% certainty, but as an ex-recording engineer, I don't think the sampling rate has anything to do with the frame rate, so I don't believe that the 48 KHz sampling rate was chosen to "fit" 24 frames. I think it was just a matter of wanting a slightly wider frequency response. A 48KHz sampling rate can handle frequencies up to 24KHz and the 44.1 KHz sampling rate of standard CDs can handle frequencies up to 22KHz (the extra ".1" was for a margin of error on early filters). This is all based on the Nyquist Theorem where the sampling rate must be twice the highest frequency you wished reproduced. Also, while CDs are 44.1/16 bit, professional audio digital recorders have been 48/24 bit for many years now. (Some even sample at 96KHz). That's where the 48KHz sampling rate comes from. (If you have documentation proving otherwise in regards to the 48KHz sampling rate, please point me to it.).

[lagunaseca]

Originally Posted by ZoetMB

Sorry, there's a lot wrong in your post. Analog TV did not broadcast at 24 or 23.997. It broadcast at 30fps originally and had to switch to 29.997 when color came in. But all this applies only to analog TV. 24 fps movies were converted using what's called a 3:2 pulldown to 30fps (or 29.997 once color came in) for broadcast. You can lookup what that means..too many details to note here. TV shows recorded on video were recorded at 30fps (or 29.997).

The reason why color analog TV had to change the 30 fps rate is because the 3.58MHZ color subcarrier would absorb common phase noise from the harmonics of the line scan frequency. So they adjusted everything else except the audio and chroma subcarriers, including the frame rate. So they took the 30 Hz frame rate (not 24) and divided it by 1.001 to get 29.97.

But then they also had to adjust the SMPTE Time Code because at 30fps, an hour of timecode was longer than the wall-clock time by 3.59 seconds. That would lead to an 86.16 second error per day, something unacceptable for television scheduling, especially when it became automated.

So SMPTE "Drop-Frame" Timecode drops frame numbers 0 and 1 of the 1st second of every minute, except when the number of minutes is divisible by 10. Note that the video frames aren't actually dropped, just the timecode frames are dropped.

But drop-frame isn't actually used much anymore. I know this because I was responsible for the development of an application used by the industry that incorporated asset metadata, including SMPTE timecode. When we asked all of the clients whether we needed to support drop-frame, everyone said no (but I left it in anyway as an option).

As for audio, I can't say I know this with 100% certainty, but as an ex-recording engineer, I don't think the sampling rate has anything to do with the frame rate, so I don't believe that the 48 KHz sampling rate was chosen to "fit" 24 frames. I think it was just a matter of wanting a slightly wider frequency response. A 48KHz sampling rate can handle frequencies up to 24KHz and the 44.1 KHz sampling rate of standard CDs can handle frequencies up to 22KHz (the extra ".1" was for a margin of error on early filters). This is all based on the Nyquist Theorem where the sampling rate must be twice the highest frequency you wished reproduced. Also, while CDs are 44.1/16 bit, professional audio digital recorders have been 48/24 bit for many years now. (Some even sample at 96KHz). That's where the 48KHz sampling rate comes from. (If you have documentation proving otherwise in regards to the 48KHz sampling rate, please point me to it.).

Yes, you're right about broadcast not being at 24fps. Sorry about the bad info. But we both agree on why we have the fractional frame rates (because of color). Previous posters were mentioning different reasons of why we don't have 30fps, so I wanted to correct that.

As for the audio you ideallly want video fames to line up with audio "frames" evenly. It becomes time consuming to sync audio and video if the Hz aren't evenly divisible. Below are 2 articles I found. But as you said AV sync isn't the major reason for 48khz, it's just one of the many reasons.

http://www.tvtechnology.com/opinions...uestion/184354

https://www.provideocoalition.com/al...khz-learn-why/

[Wendell R. Breland]

Another reason to chose 3.58MHZ color subcarrier is the subcarrier itself will create diagonal lines on a black and white TV. If an even multiple of 30 was used then the subcarrier would produce vertical lines. IIRC, test showed the vertical lines were much more noticeable than diagonal lines.

[Wendell R. Breland]

As to 23.976 being = 24 it is not, see Table 1 in SMPTE 274.

Folks need to remember there is still a lot of NTSC video in use today hence 59.94 in the world of HDTV. Don’t know as fact but suspect BD uses 23.97 as it should work well on all ATSC sets.

[e_d]

Here's a related question: why are some European films that are filmed at 25 frames per second slowed down to 23.976 - 24 fps for Blu Ray? Why not leave it at 25 on the disc?

[Naiera]

American TVs wouldn't support that, for the most part.

[e_d]

But European countries support the 23.976-24? Interesting.

[Naiera]

Of course they do. 60Hz support was extremely common in the 90s and early 2000s on CRT televisions.

Most European Blu-ray releases are 23.976 or 24.000Hz. This would complicate things if our screens didn't support that...

[Caprica_U-87]

Found this thread when I was wondering why my region 2 "death of stalin" blu ray is 24.000 fps. Strange.