24p to 25p or 25p to 24p

[Alexander Fijlstra]

Hi Everyone,

Can anyone give me some advice on the following:
We'll be shooting a shortfilm next month on the Red One and now we need to decide if we want to shoot 24p or 25p. I'm living in the Netherlands, so 25p would be te most straithforward decision for dvd/blueray output. But most of the filmfestivals in Europe only accept 24fps on film. So then we have to do the convertion to 24p.

In short, we need to output both 24p (for film) and 25p (for dvd/blueray)

Will there be any differences in the convertions? I read somewhere that the audio can get phase problems when converting from 25p to 24p.

Then i get to my next question, is t necessary to slowdown/speedup the complete audio and video. Isn't it possible to only convert the video to the desired framerate and speeding it up/down to the original audiolenght?

If anyone can shine some light on this, please do, thanks in advance.

 

[Graeme Nattress]

24fps <-> 25fps conversions are best done by speeding up / slowing down the video by the 4% needed, keeping a frame for frame correspondance.

For the audio, Europeans have lived with 4% sped up audio for ever. But you can now do the audio speed up / down and pitch-shift the audio back to where it was, for a pretty seamless conversion.

Graeme

 

[Craig W. Bickerstaff]

Shoot 24p and do the blu-ray disks in 24p for DVD you can go up to 25 but you may as well just do NTSC disks, these days pretty much any TV you come across will play back NTSC.
Converting from 24 frames to PAL will require the film to be sped up by a small fraction and this will increase the pitch of the sound to a small degree, you don't really notice unless you have the original to compare too so for most people they don't really care.

 

[Adrian Sims]

If you are editing in Premiere you can right click on a 25p clip (say a continuous .avi of your entire film) in the Project Bin and choose 'Interpret Footage'. Set the 'Assume This Frame Rate' option to 24 and you will notice the clip duration changes by the above-said 4% (movie runs 4% longer). Now drop the clip into your 24p timeline and you are good to go. Works in reverse as well (24p to 25p), but the movie will be 4% shorter in duration. Ideal for servicing both the European, Pacific and American markets - just change your running time on the DVD slick!

 

[Alexander Fijlstra]

Thanks everyone!

So the conversion will work, now the only question remains, will there be any quality difference if you're going 24 to 25 insted of 25 to 24. For me personally, i'll like to go for 25p. Because it's the standard, it's very handy in the whole creation process, and only at the very end there will be a conversion for filmprint. My only concern is the audio, especially after ready the following:

For example, if a project is shot at 25fps any film theatrical release will require a change to 24fps. For
the image, playing 1 frame per second slower is not an issue. The human eye cannot really see such
a small speed change.
However, if audio is played 1 frame per second slower the associated pitch change can become very
obvious. To overcome this audio tends to undergo a pitch change process, during or after the speed
change, to maintain the correct audio sound. The issue with this is that the process of changing the
pitch and adding new audio samples to slow the original 25fps audio to 24fps can introduce phasing
errors between stereo channels, making left and right audio go out of sync.
Speeding up audio - from cinema's 24fps to tv's 25fps is a far easier process as samples can be
removed equally from both stereo channels.

Anymore advice? I really appreciate the help.

 

[Kamran]

24p is always better choice when you are going to output to 35mm.
for DVD/Blueray mastering you can speed up your film (both video and audio).

What is your editing system? If you work with FCP, you can always use Cinema Tools for this kind of conversion. It is fast and straightforward.

Shooting in 25p is not a good decision for film out, film duration will increase (100min would be 104min)
and you must convert your sound to 24fps which in most cases will not yield perfect results.

Kamran

 

[Filip Vandoorne]

24 or 23,98 is perhaps better as universal master for HD, SD and cinema distribution.
- we are mostly used from american tv series seeing 24 of 23,98 been
speed-up to 25 fps.
switching from 25 to 24 would slow down the pace of the movie a bit. What is worst for your movie? slowdown or speedup? - also keep in mind that you total time will be different between the cinema 24fps and the SD?HD? 25fps versions
- for the offline and especially online, check that you viewing monitors have native support for 24,or use 23,98 because then it's more easily to do a 3:2 pull down to make a 59,97 hz signal for you monitors - although with the recent firmware update the blackmagic hdlink pro can make a very good conversion from 24 to whatever your monitor supports.
We use with succes the Eizo HD2442w with 23,98, 24 and 25fps natively.
Only for 23,98 and 25 it will be possible to do a realtime conversion to a standard definition CRT broadcast monitor during offline - could be important if you want to make dvd's during the edit proces, or will you use a computer for reviewing edits? if you really want to make 25fps dvd's during the edits, it will take time as you will each time have to do the conversion proces of video and audio. try to stay for reviewing on the editing workstation or make quicktimes for reviewing on computers - that could be connected to a large screen/projector.
- for digital cinema - dcp - 24 is used, but you can use Apple Cinema tools to conform you final film from 23,98 and 24 and 25 fps to whatever you need.
Do this conforming on a video-only quicktime, and do the audio conversion separately in Soundtrack, so there is no audio pitch change, and all remains exactly on 48khz and assemble then the modified sound and video back together in QT player or Finalcutpro
-during recording with an separate audio recorder, take care that audio is using the same timebase as the camera - 23,98 - 24 - 25 -Also, if they say 24 do they really mean 24 or 23,98??? finalcutpro is also mixing those up in the descriptions of the presets/easysetups ! check and doublecheck....
-if sound postproduction is done on another system, check beforehand that they can work with 23,98 - 24 or 25fps recordings and edl's/omf's/xlm's.