Dropped frames in 4K recording

damienlovegrove · Aug 10, 2017

I understood that the Mavic Pro writes 4K at 60mbps (mega bits per second) and that is only about 8Mb per second. Well, I think the 60mbps must be a typo and they mean 60Mb/s as slower cards (600x) are dropping frames. I have a few Lexar 600x 32GB micro SD HC1 cards for my Phantom 2 GoPro Hero 3 and they worked fine. In the Mavic they drop frames so I decided to check the Sandisk Extreme 16Gb card that came with the Mavic and it doesn't drop frames. I then bought some Sandisk Extreme Plus 64Gb cards and they are fine too. Here are the results of testing these cards with the Black Magic Disc Speed Test utility via USB3 ports on MacBook Pro (mid 2015). All speeds are MB/s (mega bites per second)

Lexar microSD 600x 32GB: Write speed 40.7, read speed 89.6
Sandisk extreme 16GB: (came with Mavic) Write speed 64.6, read speed 90.8
Sandisk Extreme Plus 64GB: Write speed 85.3, read speed 90.4

I just thought I'd share to save you failing to save money by buying cards that are not up to the job.

Cherryhead · Feb 21, 2018

Buddy you saved my life

mdw · Feb 21, 2018

Mavic 4K video has bitrate 60 Mbps (megabits per second, not megabytes!). For completeness, megabytes per second should be written as MBps but the usual way is MB/sec or MB/s.

Nathan Hoover · Feb 21, 2018

Interesting - thanks for the warning. How do you notice the frames are dropped?

Memaddog · Aug 7, 2018

Nathan Hoover said:
Interesting - thanks for the warning. How do you notice the frames are dropped?

This just happened to me. I use a Samsung 64GB U3 card and even though it's rated at 60MBps write, when I started recording more 4k footage, I started seeing dropped frames. I noticed when I had the footage in Premiere. Just watching the clip via Quicktime wasn't obvious as Quicktime just duplicated the preceding frame to cover the missing one, but in Premiere, I get a nice solid green frame so it stands out. I think the safer bet is to use a card that's rated higher than the necessary speed.