Hi. I have an Iphone 6 (original). I've been experiencing problems with laggy video for around 1-2 months now, quite frustrating. So if you're like me - don't feel alone. I have read just about every forum post on the issue, and tried everything other than downgrading firmware/app version. I was experiencing the laggy video before the 'CPU warning' appeared. Then the CPU warning started appearing as well. With 4.1.3, CPU warning gone, video feed may be better, but the lag issue is still there.
I have experienced severe lag issues when using the active track mode, which I expect is computationally expensive. It's as if there is a real bottleneck with the processing power of the Iphone. I have seen someone else post a similar observation.
The video off the SD card itself is always perfect. It is an issue with the image transmission, and I guess - the IPhone + App.
Here is the complete list of everything tried, after reviewing 'every post'. It's hard to say whether these things 'improved' anything, but I would say generally - they didn't, and the problem seems to be still there:
1. Airplane mode on Iphone (prevent interference from wireless/cellular on mobile and controller transmission)
2. Use a USB cable into the USB port at base of controller (on basis that the other smaller cable on side is 'dodgy')
3. In Iphone settings / general / Background App Refresh, disable background app refresh.(on basis that other apps interfere with DJI Go)
4. On Iphone, double press home button and swipe up to close all other apps.
5. In DJI Go, general settings, disable 'cache during video shooting'. I now don't have a local copy of video, the theory was that this was too intensive on the Iphone.
6. Factory reset the Iphone and reinstall with only the DJI Go App.
7. In DJI Go Image Transmission settings, click 'Custom' channel mode , select 10MHz bandwidth (on the basis that this is less intensive transmission), and manually pick a frequency with low interference. PIck 'Normal mode' for image transmission.
Still left to try:
1. Flying in a variety of greater locations, to understand whether I am suffering from local signal interference in urban areas. I think when I flew somewhere further from urban areas the problem almost went away. It's really hard to measure, and between full time job and family, the time left in my day to be DJI's guinea pig is rather limited....
2. Further testing using my wifes Iphone 6. When I tried this once, it did appear better than on my Iphone 6. Maybe. Hard to tell.
3. Firmware and app downgrade. I read the instructions on this forum and it seemed complicated, and frankly I don't want to mess with things I don't understand.
4. Learning to live with a bit / some lag. I guess this is hard because I have the perception that others are using the mavic, flying out 7km and have no lag issues ever. That makes me think I have a problem.
Sigh.