At NAB 2019, I asked the lead programmers at FiLMiC Pro whether the VFR (variable frame rate) recording situation remained the same, in order to help you —our reader— to both understand and follow best practice regarding framerates when shooting on iOS, and later editing and distributing it. At their booth in Las Vegas, FiLMiC engineers reaffirmed something that hadn’t been mentioned publicly since my 2017 article called Understanding iPhone framerates for shooting, editing & distribution. Ahead I’ll update that information.
Introduction
When you shoot video on iOS (including iPhone, iPad and iPod Touch), framerates don’t work the way they do on conventional camcorders, which use CFR (constant frame rate). That’s because iOS video recording uses VFR (variable frame rate) with only approximate targets, not exact framerates. This is true, whether you shoot on iOS with FiLMiC Pro or MoviePro. The way framerates work when editing video on iOS is also different, although when you share (export) from an app like LumaFusion, they can go back to the traditional way of handling things as CFR. Ahead you’ll learn how to handle iOS footage, whether or not you edit and grade your iOS footage on a traditional computer or on iPad/iPhone/iPod Touch.
Framerate workflow for iOS
1: Shoot with an app like FiLMiC Pro or MoviePro in the approximate target framerate.
As I have covered in great detail in many past articles (including Video framerates and the Tower of Babel: a translation guide, illustrated above), exact rates like 30.000 and 60.000 haven’t been standard since before 1953. Many standalone cameras and apps unfortunately round the standard 29.97 and 59.94 (also rounded numbers, but precise enough for our purposes) to the closest integers, “30” and “60”. In the case of physical, dedicated cameras, those rounded numbers usually refer to 29.97 and 59.94. In the case of apps in iOS devices, to my knowledge, all iOS camera apps including the iOS camera app, FiLMiC Pro and MoviePro shoot at VFR (variable framerate) for efficiency’s sake, and the framerate you choose before shooting is only a target, not a final framerate. Generally speaking, any shooting app that doesn’t offer you any framerate choice has a target of ±30 fps only. Both true 24.000 and 23.976 (aka “23.98”) are indeed standards today, and it’s important to know which to use when exporting (sharing), less so when shooting with iOS devices.
FiLMiC Pro, MoviePro and even the still not quite baked Adobe Rush have targets for ±24, ±25, ±30, ±50, ±60 and more. (I wish all iOS and Android developers would add the ± symbol in front of each framerate to clarify this.) So for this and many other benefits these apps offer, you should be shooting with FiLMiC Pro, MoviePro or some other professional app.
- If you want your final product to be 23.976 fps, shoot with ±24 in your desired shooting app. Of course, set the audio to 48 kHz. (Adobe: Please fix the raw audio sampling frequency in Rush.)
- If you want your final product to be 24.000 fps, shoot with ±24 in your desired shooting app. Of course, set the audio to 48 kHz.
- If you want your final product to be 25 fps, shoot in ±25 fps in your desired shooting app. Of course, set the audio to 48 kHz.
- If you want your final product to be 29.97 fps, shoot with ±30 fps in your desired shooting app. Of course, set the audio to 48 kHz.
Unless you are shooting and editing specifically for a 720p TV station, I recommend avoiding the use of 50p or 59.94p as a final delivery framerate, since its distribution beyond 720p TV stations is quite limited, with multiple millions of iOS and Android devices in use that can’t play more than 30 fps. Only a few of the latest devices can handle playback up to 50 fps or more. So if you innocently were to produce a final product of 50 fps or higher, most of your viewers will end up seeing half of your intended framerate, and the shutter speed you used when shooting will no longer match, and you would no longer have a consistent motion experience on multiple screens. Stay under 30 fps as a final delivery rate unless you are specifically producing for a 720p TV station, like the ±41 in the US I listed in this article or for a private showing where you know you can play at higher than 30 fps, aka a corporate presentation with an HDTV or projector that you know can support it.
2a: If editing on a traditional computer
If you are going to edit the iOS shot footage on a traditional computer, be sure to use a video editing app that definitely supports VFR source material (or transcode first). Since at least 2013 (if not earlier), FCP X has supported VFR, but Premiere CS6 did not. (See my 2013 article: Why Manuela returned to FCP after loving Premiere Pro CS6?)
My friend and seasoned video editor Rubén Abruña of EditingTraining.com has carefully confirmed that the latest versions of DaVinci Resolve and Premiere Pro CC fortunately now handle VFR properly (unlike the intolerable situation experienced by Manuel in the aforementioned 2013 article), and only occasionally Rubén had to correct for a small audio/video out-of-sync situation, i.e. 2 or 3 frames, but only occasionally. In Manuela’s case back in 2013, there was no consistency in the playback to be able to make such a simple correction.
In case you are still using the old Adobe Premiere CS6, it definitely does not support VFR. If you have problems with VFR footage in your editor, either upgrade to an editor that does support VFR, or transcode to a CFR (constant frame rate) using a program like the free Handbrake, and set it to output to the exact desired framerate, be it integer (like 24 or 25) or non-integer (like 23.976 or 29.97).
Set the project (timeline) in your software video editor manually for the desired target framerate. Do not let the project (timeline) set itself automatically based upon the first clip.
2b: If editing on iOS
The latest version of LumaFusion for iOS (which I have covered in several past articles) now supports non-integer framerates even at a project level, not just upon sharing/export as before. So if your version of LumaFusion offers non-integer framerates (or if you can update it in your iOS device), be sure to select the desired framerate manually as you create it, just as indicated in the above section for conventional computer editing. For example, choose 29.97 if that’s what you want. Note that currently, LumaFusion rounds 23.976 to 23.98 in the menu. Both numbers are actually rounded, and are used interchangeably in the industry, although I prefer to express it as 23.976 as covered in detail in this article.
- 23.976p (currently expressed as 23.98 in LumaFusion’s menu) gives you a filmic cadence while maintaining compatibility with broadcast television in NTSC or ex-NTSC regions, and is also compatible with the web, DVD and Blu-ray.
- Exact 24p is for film-out/DCP or web, not for TV broadcast or DVD. Exact 24p is also compatible with Blu-ray.
- 25p is a similar cadence as 23.976 or 24, but matches the television framerate in PAL and ex-PAL regions and also works for DVD and Blu-ray, although you may have to make it 25PsF (quasi 50i with the same information in each artificial field) depending upon the software you use to author the DVD or Blu-ray and how the user interface guides you. Only do the PsF thing if the authoring software doesn’t allow you to keep it native.
- 29.97p matches the television rate in NTSC and ex-NTSC regions and also works for DVD and Blu-ray, although you may have to make it 29.97PsF (quasi 59.94i with the same information in each artificial field) depending upon the software you use to author the DVD or Blu-ray and how the user interface guides you. Only do the PsF thing if the authoring software doesn’t allow you to keep it native.
Later, choose the matching framerate in the sharing step in LumaFusion.
See the related articles
- Video framerates and the Tower of Babel: a translation guide
- When exact 24 fps beats 23.976… and when it doesn’t
- FiLMiC Pro announces FiLMiC Audio app at NAB 2019
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