I just did the following experiment to measure Spark video latency :

I take a small flashlight
The Spark is film the control device
The flashlight is next to control device as seen on attached picture
I'm filming the whole thing with an external device
Then I turn light on (cf. attached video sequence)

Repeat the sequence to be able averaging

In video editing software, I then count the number of frames it takes between first frame with the flashlight on, and the first frame with the "picture in picture" flashlight on
(this gives twice the frames latency). My external filming device is 29.97 fps, so latency in seconds is then "frame count" / 60

Some results : I've been doing the test (20 light on/off sequence for each setup) on my CrystalSky with :

Android DJI GO 4 4.1.14, OTG : 6 frames latency without any "peaks"
Android DJI GO 4 4.1.14 FCC mode, Wifi : 6.5 frame latency with regular peaks to 16-18 frames

Android DJI GO 4 4.1.18 FCC mode, Wifi, 11.5 frames latency with regular peaks to 26-29 frames

Would be nice if other users can do the test and share the reults with precisions on :

- control device model
- DJI GO 4 version
- OTG or no OTG

Also take care closing all non usefull apps to avoid unwanted extra delays...

No one willing to take advantage of winter weather conditions (in Northern hemisphere...) to make the experiment and share results ?
I believe that would be nice to get a more complete picture of differences between Android / iOS versions and also about control devices...

Interesting. I also use the CrystalSky and it feels that it has lower latency than other devices I tried. Very happy with it!

I'm not saying it has higher or lower latency... What I've seen is a latency that depends quite much on the DJI GO 4 version (o nsame device)
That's why it wuld be nice to have more objective measures.

The 4.14 version is perfectly in the advertised 180 ms latency (that's the figure on DJI website for CS) with latest 4.18 version, i found it was quite above (but would like to make sure it's same for others...)