Editing 4K on the new 15″ MacBook Pro

When the new Mac Pro was previewed at this year’s WWDC, Apple said it would be great at editing 4K.   4K is the next size up from HD – twice the pixels horizontally and vertically: four times the detail. UHD is the consumer brand name for TVs that can show 3840 by 2160 pixel footage.

Apple also mentioned that a new version of Final Cut Pro X is being prepared to make the most of the new machine. However, Final Cut Pro users have been able to create high resolution timelines since the mid-00s.

Although it has been possible to create 4K timelines for many years, smooth editing of 4K footage requires instant playback of more than one stream of video footage at once. For example if you had clip A transitioning to clip B while clip C is overlaid as a picture in picture, your editing software would have to play back clips A, B and C at the same time – changing the transparency of clips A and B while scaling clip C.

Up until now, there have been two strategies of dealing with high quality video on systems that are too slow: wait for the computer the render the video to a single combined clip which can then be played back, or to make lower quality versions that can be edited without rendering.

What could the next Mac Pro / Final Cut Pro X combination bring to 4K editing? The ability to import 4K clips and to work with them instantly – playing more than one at the same time without having to wait for rendering.

Two problems need to be fixed to make this work – fast enough hardware to decode large amounts of video information and a fast enough connection to the storage to get large amounts of data onto the screen.

This week I received my new 15″ MacBook Pro. As the SSD is now connected using PCIe instead of SATA, I knew that its storage connection speed would be much faster. Here is the result of using Blackmagic Design’s Disk Speed Test application:

To give some perspective, I recently added a 750GB SSD to my SATA-connected mid-2009 17″ MacBook Pro. The Disk Speed Test result was 206 MB/s write and 265 MB/s read.

[Tuesday update: Mac4Eevr and 9to5Mac report that the SSD speed on my Mac is even faster than is reported here. The hint from the screenshot above is the the Blackmagic software reported that write speeds are faster than read speeds – which is very unlikely given SSD technology]

This new faster PCIe connection method is the same as the one advertised for the Mac Pro coming in December. Does that mean the new MacBook Pro can edit 4K video smoothly? It will do if the GPU is fast enough.

I decided to test to see if my new Mac can edit 4K well.

I don’t have a 4K monitor or a UHD TV (which can be connected to the new MacBook Pro using the HDMI connector), so I simulated a 3840 by 2400 display using QuickRes – a shareware app from thnkdev. As far as Final Cut Pro X was concerned, a bigger than 4K screen was attached.

I generated 4 two minute 23.98 frames pet second 4K clips which I encoded as ProRes QuickTime movies – 7 GB each. The rotating globe helps to see how smooth playback is. Behind the globe is randomly generated noise which is harder to decode from the source files.

I imported them into Final Cut Pro X without creating proxies or making optimized versions. I turned off background rendering.

As I don’t have a 4K camera, I set up my Canon 5D Mark II (on a wobbly tripod) to record the results:

Click the cog (to the left of the YouTube logo) and choose the 1080p version from the pop-up menu.