iphone XR jerky/skipping/stuttering playback and rendering

Hi

I am hoping someone can help here.

The problem:
When playing an iphone XR clip on the DR timeline and when playing a copy of the same clip rendered by DR, outside of DR (using say VLC or any other video player), the clip appears to be skipping/stuttering. The original clip played on VLC or the windows default player works fine and plays without any skipping.
In other words, the problem occurs:
- When playing the clip on the DR timeline
- Playing rendered output from DR, on any video player outside of DR (VLC for example)
This problem appears to be isolated to the iPhone XR and perhaps other iphones.

Background
I edit videos for my daughter who is a teacher. She gets video clips from many different sources and I edit them into a video for display at the school. My daughter has said that the videos I render play jerkily on their video player and I have been able to replicate this on an Android TV playback device. I assume many of the parents and teachers who provide video clips use iPhones.

Not all the videos I render have problems. Any video which I have done based on one of my video cameras or from my Sony or Canon DSLR play well without issues.

To be more specific, I have uploaded 2 clips to the cloud to demonstrate the problem.
- The original from the iPhone XR clip (1920 x 1080, 60.02fps)
- The same clip processed by Handbrake v1.6.1 (1920 x 1080, 60fps)

My Workstation
Windows 11, 64Gb RAM, RTX3060 with 12Gb graphics, i7-8700, 8Tb SSD and M2. With this configuration I can easily (smoothly) play videos from my Sony A7 IV at 4K/50fps on the DR timeline without any of the issues I encountered with iPhone XR clips. Videos render without any issues.
I am using DR 18 Studio. The problem has presented itself in all versions of DR including 18.1.3 which I downloaded yesterday.

What I have already tried
I have tried the following with no improvement
Performance: Both proxying and generating optimized media. This does not explain why the rendered clip is also jerky.
Variable frame rate: The clip downloaded from the iPhone XR has a frame rate of 60.02. I used Handbrake to convert the clip to a frame rate of 60. Both clips play smoothly in VLC.
Timeline frame rate: Tried different timeline frame rates including 60, 30 and 24.
Rendered output: Have tried different output formats (quicktime, MP4), different codecs (h264/5, DNXHR), different frame rates (60,30, 25), fixed and variable bit rates, and lookahead.

Video files
The clip named "Original.MOV" is the file as downloaded from the iPhone XR. The file named "Extract with HB.mp4" is the Original.MOV clip processed by Handbrake. The only option I selected in Handbrake was the change to 60fps. The 2 files have been zipped. The zip file can be accessed from Dropbox or OneDrive.

https://www.dropbox.com/s/pmqf839yet35g ... R.zip?dl=0
https://1drv.ms/u/s!ApTfRwDjlD3gif4i9cs ... A?e=fL86CB

Any help would be appreciated

thanks
Greg

Since you mention playback on a TV, it might be because the frame rate of the clip is 60fps and you're in a 50Hz country.

Modern TVs can usually switch to match the input frame rate but a lot of playback devices will be setup to output a fixed frame rate regardless of the video content. If it's set to 50 you will get motion artifacts playing a 60fps video.

Since you mention playback on a TV, it might be because the frame rate of the clip is 60fps and you're in a 50Hz country.

Thanks Roger
I don't think it relates to the TV refresh rate. The original file plays OK on the TV and computer. Its only the rendered video that has a problem. My Samsung S20+ videos recorded at 60fps work fine. The problem occurs in the timeline and the same problem with the same jerkiness occurs with the rendered clip (ie delivered by DR).

regards

Unfortunately, your original frame rate is not constant, like from most smartphones.
I can reproduce that occasional jerkiness here in DR, but I’m not sure you see the same. It’s rather like the stabiliser trying to catch up with panning. And then, you have some pulsing of the light on the walls from the frame difference. I'd suggest avoiding smartphone footage, if you can.

If you have an Apple computer around, its simple editing app iMovie might be able to handle the iPhone footage better than DR.

Unfortunately, your original frame rate is not constant

Thanks Uli. I did convert the footage to 60fps using Handbrake so I was wondering if you were able to check the second clip. Both, unfortunately for me, had the same problem. I am not sure what it did with the extra frames

I checked both. While I read from some folks here that they can work with phone footage without difficulties, I've seen similar issues again and again.
You may want to try FiLMiC Pro. While I have the legacy version only, some folks claim that it can record constant frame rate on recent phones. Plus, you can set it to 25 or 50 fps.