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25fms to 24fms conversion

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Nic Lush
25fms to 24fms conversion
on Apr 8, 2012 at 4:18:30 am

Howdy hoping someone here can help.

I have a 1080 25fms E- Cinema file , 5.1 audio.

Im using Doremi's CineAsset ( will only convert stereo audio ) and easyDCP (will do 5.1 and image sequence)

Most cinemas will only accept 5.1. I have tried converting the movie but have I still get the frame skip every second...i cant seem to get the imagery converted to 24fms correctly.

Is there a DCP wrapping app that will ingest a 1080 mpeg with 5.1 and do the frame conversion...or software (After Effects) to convert 25 to 24fms correctly??

I had a play with Andrew K (VCP) Frame conversion plugin but i was looking at 190hrs of rendering :(

thanks for any help anyone can offer



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Jeff Brown
Re: 25fms to 24fms conversion
on Apr 8, 2012 at 2:27:05 pm

A common way to do 24 <--> 25 FPS conversion is to just reinterpret the footage as the frame rate you want. I.e., tell AE that your footage is 24FPS. Then: use audio software to make the soundtrack match without any pitch-shifting.
One caveat:
IF you are doing this for video-based playback (like BluRay), you may actually need 23.976 FPS and a corresponding audio file.

IF you are doing this for digital cinema, they may be happy with 25 FPS. Do you have specs from the venue?


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Dave LaRonde
Re: 25fms to 24fms conversion
on Apr 9, 2012 at 4:29:24 pm

[Nic Lush] "Is there a DCP wrapping app that will ingest a 1080 mpeg with 5.1 and do the frame conversion...or software (After Effects) to convert 25 to 24fms correctly?"

I'm not aware of one. But since it sounds like you're beyond the picture lock stage of your edit, you may be able to back up a bit and do a frame rate CONVERSION (don't conform!) in your NLE to either 23.976 fps or 24 fps: you'll naturally want to double-check your delivery specifications before you do this.

Re:Vision makes a plugin called Twixtor that should do the job for you, it's available for many different editing applications plus After Effects, and you can download a tryout version. You're probably aware that AE can't deal with 5.1 sound, so it may not be the best choice.

Sorry to learn that you chose the wrong frame from the start.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA

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Andrew Somers
Re: 25fms to 24fms conversion
on Apr 10, 2012 at 2:53:55 pm

I've used AE to covert feature films shot at 25 fps to 24 with no problems.

History: back in the days before inexpensive 24P cameras, independent filmmakers would shoot in PAL DV, and then convert that 25 to 24 fps, and this would result in a *very* film-like look. In fact, the very first version of "Magic Bullet" was targeted at this specific task.

The principal issue is that there is a 4% speed change in the footage. This 4% is a common issue in the interchange of media from NTSC and PAL markets. In general, the preferred conversion method from NTSC to PAL or vice versa uses 24 FPS as the intermediate stage. In NTSC to PAL, fields are dropped to bring the interlaced 29.97 footage down to 23.976i. Then this would be sped up 4.1% to 25 fps. PAL to NTSC used the reverse of this path.

In the case of music content, it might become necessary to use a pitch shifter (such as Lexicon PrimeTime) to adjust the pitch due to the 4% change.

Your case:

So, it appears what you have 25 fps HD footage? The conversion is simple: In Aftereffects you can:

1) Bring in the footage and interpret it as 23.976 (or 24.00 depending on your delivery requirement). However, in this method you will need to convert the sound in a separate application, such as ProTools (this is preferable to After Effects, as ProTools has substantially better algorythyms for sample rate conversion).

1b) In this method, bring the sound into ProTools and sample rate convert it. If your sound is at 48K at 25 fps and you are going to 24 fps, then interpret the sound as 46080 Hz, and convert to 48000. If you are going to 23.976, then interpret the sound as 46033.966034 Hz. See the attached PDF document for more conversion numbers.


2) Or, bring the footage in via AE, interpret it at its present rate of 25, and then use time remapping to convert it to 24 or 23.976.

Andy's List of Pulldown Numbers

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Andrew Somers
Re: 25fms to 24fms conversion
on Apr 13, 2012 at 5:00:02 pm

Chris said: "Your numbers are off, 104.2708333 is wrong, should be 104.2709376, so is 50050.0, should be 50050.05005005006. When you're talking about 2+ hour movies, a single frame can be off."

No, my numbers are CORRECT. Your numbers are off because you are ROUNDING.

In relation to pulldown, the true ratio is 1001/1000. This results in periodic decimals (infinitely repeating) for many of the conversion numbers.

For instance, the commonly used 23.976 is actually rounded from the periodic repeating decimal 23.976023976023976023976...

In practical reality, some software applications round off at three or four decimal places, though this is incorrect and will result in drift. Some will report the rounded number to the user, but will internally use the correct number at least out the the limits of double precision variables.

There are 172800 frames in a two hour movie - rounding at 4 decimal places will produce a drift of more than one frame over that period.

NOTE: 0.1% is only correct when pulling UP. When pulling DOWN, it is actually 0.0999000999000999000....% To understand this math, consider that if you take a value of 100 and increase it to 150, you have increased it by 50%. If you then take 150 and reduce it back to 100, you have now decreased it by 33.33333 % (this is a common concept for investors, that a 33% loss requires a 50% gain just to break even).

The "true rate" of 23.976 is

23.9760239760239760239760239760239760... (infinitely repeating)

When calculated on a calculator with 25 digits precision, the rate change from 25 to 23.976023976... is:

To keep a two hour film in sync within a frame, you need a minimum of 8 digits of precision (that is, 6 digits after the decimal point or 23.976023)

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Garrett Sergeant
Re: 25fms to 24fms conversion
on May 12, 2012 at 8:46:36 pm

If you are on a Mac then the easiest workflow is using the Final Cut Suite

Open your film in Cinema Tools and use the conform tool to translate your 25fps material to 24fps. This should take effect instantaneously.

The video file should work fine at this point in any program, but a lot of programs have trouble working with the audio. You will need to re-sample it in order for other programs to interpret it correctly.

Open the movie in Final Cut Pro and throw it into a sequence. Re-Export. Done. You now have a working, conformed, re-sampled movie.

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