Yes it has been extensively tested, the write speed is a fixed rate. Not uncommon at all with cameras, many cameras use a slow write speed. Lots of things are possible but with the current software/hardware the write speed is limited. That is not the only limitation of the system, the video processor is another one as noted above.
Alan
Understand the other limitations, though given that the GoPro forces 480p secondary out versus the 720p (alleged at least) on the P3, there must be some differences. That and each implementation of the same chip tends to have slight differences.
On further researching... if you look at the tear-down of a GP Hero 4 Black, versus the Phantom 3 Pro camera, you'll see that while they do appear to both contain an Ambarella A9 SoC, the associated supporting silicon is different. There's always some package for RAM (often combined with some NAND), but there also appear to be at least 2 additional large packages on the Phantom 3 that are not included in the GoPro. Possible DJI is cheap, and rather than uses more expensive PoP, they're using more individual chips... but also possible the differences between the two are deeper than it appears.
As far as the sdcard performance, any links to where this has been thoroughly tested? I did a little searching, but couldn't find anyone who posted actual data on the P3 Pro/Adv. I'm out of my home country at the moment, without my birds, but can test it myself when back.
Unless I can find that it's positively been done before, I propose to do:
10-15 photos on each type of card, average it, and see the results.
Testing w/ JPEG vs RAW + JPEG and some of the burst/HDR shots as well.
I have two different Class 10 from different manufacturers, 1x UHS-1, and 1x UHS-3 cards. While I wouldn't bet money, I expect they won't all perform the same. This might be due the camera or might be due to the manufacturer of each MicroSD, but I'll do some quick stats and see if indeed higher speed cards decrease time between shots with any statistical significance.
My understanding is that "time between shots" is dependent on how quickly the Ambarella can flush the connected NAND to the MicroSD interface. Perhaps it's fixed... or perhaps it's more opportunistic.
The 60 mbit/s video limitation could be something further "up the chain", as
@ianwood suggests, and not dependent on the ability of the SoC to flush the NAND to the MicroSD. The internal ARM cores in the Ambarella are variable clocked (though it may not be variable from actual model to model), so perhaps there's some headroom to be found. Wild speculation at best.
