Benchmarking and comparing video rendering times on the iPad Pro

I do a lot of video editing, mostly using Premiere Pro on my desktop or laptop, though I’ve been increasingly using my iPad/iPhone for small edits like sharing with friends or on social media, etc. As time goes on I’m beginning to wonder how feasible it is to do some more serious editing on iOS. Each of my iOS devices handles 4K video from my Panasonic GH4 or Phantom 3 quadcopter with ease. They play it perfectly, and hardly drop a frame even when scrubbing through videos. Rendering video projects is also impressively fast, and with that in mind I decided to run a few benchmarks.

I’m comparing quite a few devices, basically anything I own that will run Premiere or iMovie. The devices are:

- Desktop 'Hackintosh', Core i7 2600, 16GB RAM and (an ancient) AMD 5770 GPU
- MacBook Pro, Core i7 4850HQ, 16GB RAM, Nvidia GeForce GT750M
- Surface Pro 3, i3 4020Y, 4GB RAM, 64GB storage
- iPhone 6S Plus, 2GB RAM, 64GB storage
- iPad Pro 9.7-inch, 2GB RAM, 32GB storage

Each device is running the latest version of its OS.

Details

I made a simple video project using two 4K videos, shot on the Panasonic GH4 at 24fps at ~80mbit/s. I imported the videos straight from the SD card on each device (using the Apple SD Card to Lightning Adapter for the iPad/iPhone).1 I created as similar a project as I could on each device/program, using iMovie on the iOS devices and Macs, then Premiere on the Macs and the Surface. The bitrate for rendering on each device was set to ~23.5mbit/s, exporting at 4K/UHD. I tried to use the fastest possible settings on each device; in iMovie on the Macs, I chose the ‘fastest’ option; in Premiere I chose ‘VBR, 1 pass’ and left ‘maximum render quality’ unticked. Additionally, for Premiere I rendered twice on each device – first using the GPU/OpenCl/CUDA and again using the CPU.

I also made sure to close all other open programs on each device, and leave some time between repeat tests to account for any thermal changes.

Results

The results are pretty interesting, and once again the iOS devices impress me. Here they are from fastest to slowest:

- 00:38.15 - MacBook, iMovie
- 01:24.47 - iPad, iMovie
- 01:29.46 - iPhone, iMovie
- 04:11.41 - Desktop, GPU, Premiere
- 04:40.05 - Desktop, CPU, Premiere
- 04:44:48 - MacBook, CPU, Premiere
- 04:56.95 - MacBook, GPU, Premiere
- 05:43.34 - Desktop, iMovie
- 13:00.59 - Surface, CPU, Premiere
- 13:03.54 - Surface, GPU, Premiere

Conclusions

The MacBook with iMovie clearly beats the rest. However, while the iOS devices are a bit slower, they beat the other combinations by a wide margin. My assumption here is that there’s a hardware h.264 encoder of some kind, that’s getting used by iMovie on the iOS devices and the MacBook. The Hackintosh is at a disadvantage in that respect, and it seems like Premiere doesn’t make use of it on the MacBook either. While this test focuses on render times, I feel that the results are largely in line with my experience of the performance of each app in general usage. Scrolling through clips, trimming and doing other basic edits feels much smoother on the iPad than in Premiere.

Looking at the rendered files, I don’t see much appreciable difference in quality between them. It would be nice to have the option to output at a higher bitrate on the iPad, but the video output by each device still looked pretty good.

While the MacBook is comparable to my ageing desktop in speed using Premiere, its fans run at full speed the entire time. The desktop feels better-suited to longer workloads as a result – to avoid both thermal throttling, and excessive wear and tear from the (quite intense) temperatures the MacBook reaches. The iPad did heat up a little, though considering the differences in TDP between the chips, it’s never going to get as hot as the i7s.2 It would be interesting to test it over a longer time period to see if it does have to throttle eventually.

Coming back to the iOS devices though, I really would like to see Final Cut Pro or a fuller version of Premiere become available for them. It’s surprisingly un-cumbersome making edits with a touchscreen (helped even more by the Pencil), so it would be great to have the ability to do some of the more advanced things that one would expect in Premiere.3 I’m aware there are lots of other video editing apps for iOS, and I’ll maybe do a follow-up post comparing speed/features between them.

Here’s a quick comparison shot of the three versions. I’ve also uploaded a screenshot from the iPad render, the Desktop+Premiere+CPU render, and the MacBook+iMovie render. If anyone is interested in the actual video, here’s the one rendered by the iPad.

comparison

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  1. The iPad imported the files in 34.62 seconds and the iPhone managed it in 24.96. I wonder if the iPhone has faster storage, and the iPad Pro’s slower storage negates the need to support USB 3.0 like the larger iPad Pro?
  2. I don’t know the A9X’s max TDP, but it’s going to be a lot lower than the 47W of my laptop’s i7, or the 90W of my desktop’s.
  3. I won’t start comparing the differences between iMovie and Premiere, for anything other than basic transitions and timeline editing they’re obviously worlds apart.