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User profile for user: jerikofox
jerikofox Author
User level: Level 1
4 points

Pan with iPhone (30fps) video jerky in 25fps

I've done earlier projects with mixed fps on timeline with no problems. Now the one I'm doing is meant to be burned on DVD and BD and that's why it needs to be put out in PAL standard framerates. This project is the first I've done using only video that has been shot with iPhone 4S. I've noticed that when I do a horizontal pan with iPhone the video comes out very disturbingly jerky in 25fps. I've tried to do the project in 30fps and change it during creating the disc image (with Toast). I've tried to do the project in 25fps to begin with. I've tried to do the project in 30fps, export in mp4, import and create new project in 25fps. Everything ends up with the same result. (One thing I haven't tried yet is to edit on 25p instead of 25i, but I don't know if that makes any difference.)


So, what I'd like to know is that is it even possible in any way make my pans more smooth – as they appear in 30fps. I don't have all the originals in the iPhone anymore, but of course in my FCPX folders there are the camera native files. Or is it just a pure fact of life that pans shot with iPhone is not ever going to look nice in 25fps. (Since iPhone 4S doesn't seem to give an opportunity to choose the frame rate.)

iMac (27-inch Mid 2010), OS X Yosemite (10.10.3)

Posted on May 10, 2015 6:02 AM

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7 replies
User profile for user: David Bogie Chq-1
David Bogie Chq-1
User level: Level 7
26,590 points

May 11, 2015 10:55 AM in response to jerikofox

I'm not sure what optimizing using FCP's optimize function will do for you so post back if Ben's idea helps.


When you convert frame rates, you have options to blend frames, create new frames, or throw frames away--depending on the software you're using and how much money you throw at the software. ReVision will analyze vectors of individual pixels and create frames where none existed. And it's expensive.


A 30fps pan that takes 4 seconds to complete, contains 120 frames of moving video with maybe some motion blur depending on your shutter speed and how many degrees of arc you're covering, how fast the camera is spinning, in 4 seconds.

If you play those 120 frames back at 25fps your clip will be a bit less than 5 seconds long. That may not be what you need or want. To play that same clip back in four seconds at 25fps will only display 100 frames of your video. Your software might attempt to speed up the clip to fit, throw away 20 frames for you, or attempt to blend frames so your 120 frames will be sm-oooo-sh-ed into 100 frames. If you have some motion blur in your original 120 frames, that blur will not be consistent in the blended frames; it cannot be, there will be some hiccups.


So how do you get a smooth 25fps pan with your iPhone shooting 30fps? What if you work backwards? You still want a pan to last four seconds, 100 frames. If you shoot a 100 frame pan at 30fps it will play too quickly. How about if you double the frames you shoot at 30fps and speed the clip up by 200%? That is, shoot a 200 frame pan (not quite seven seconds) and double the speed so it runs at your desired 100 frames. Do that with frame blending activated.


I have no idea if that would work but I know the visual results of speeding something up are often less obvious than if you slow it down or throw away frames. Your software either shows away every other frame or blends them for you. Either way, it's a mathematically consistent operation that helps hide the manipulation of the frame rate change.


Hope you find a good workable solution. Please come back and tell us how your worked it out.

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User profile for user: jerikofox
jerikofox Author
User level: Level 1
4 points

May 31, 2015 4:13 AM in response to David Bogie Chq-1

The files were optimized (forgot to mention that earlier), so that really don't change a thing.


One of my friends said that if I could convert to 30fps to 150fps and then back to 25fps I might get a smooth result. But my software is not able to do that and I don't think it's doable with good quality in any cheap way.


So, inspired by David's comment this is what I ended up doing:

I made a 25i project with my 30p videos. Then I checked every clip if it appeared to be jerky. Basically every clip with any kind of pan was, other were ok – even though there were moving people etc. So, moving objects seems to transform smoothly from 30fps to 25fps, moving the camera...not so smoothly. With the jerky ones (pans) I chose from retime options to conform the speed (Automatic Speed). Meaning it will play all the frames – making the video run with "83% slow" setting. Just like David said above – to play that 4sec clip 5sec. Mostly I was using a background music, so distorting the audio didn't matter. Though I noticed that the audio didn't suffer that much. Distant speak did turn out to be more unclear, but people talking near the camera still sounded quite natural.


Just in case of someone bumps into this same problem in the same kind of situation – having a project already done: I copied the whole shebang from the timeline and created a new project with HD 25i settings. Then I pasted the copied timeline content to my new project. I had to trim the clips from here and there to make them fit the music, but I got the whole thing done with a 23min project during one evening. So, I really think it was worth the time to make this, because now the project looks nice and smooth on PAL DVD and BD.


And hats off to David for giving me something to start with.

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User profile for user: jerikofox
jerikofox Author
User level: Level 1
4 points

May 31, 2015 8:14 AM in response to jerikofox

Another option would be to change the conforming settings:

Final Cut Pro X: Conform frame sizes and frame rates


In the chapter "Choose a method of conforming frame rate" is shown different settings for Rate Conform (option which I was earlier unaware of). Default is Floor, which in this case (panning and changing 30fps to 25fps) caused the video to seem jerky. Nearest Neighbor seems to result the same (if not worse) jerking. Frame Blending reduces jerking, but causes the image to be more blurry – like it would be a bit out of focus. Optical Flow creates nearly as good result as the Automatic Speed (which I told about above), but it takes clearly much longer time to render.


So, my final statement would be that Optical Flow is good option for Automatic Speed. Automatic Speed gives slightly better quality, but lengthens the clip. Optical Flow is nearly as good and takes long to render.

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Pan with iPhone (30fps) video jerky in 25fps

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