Well, playing stuff back directly from the phone on my PC never occurred to me. I shall try that when I am at my PC to find out.
The SD card is formatted as external. Movies I download and watch are on the SD. I got it when I bought the FP2. Videos from OpenCam are saved locally though. So it does not matter where its stored.
I tried the FP2 speaker, earphones, handset or bluetooth speaker. It makes no difference.
What I did find out though is that when I
turn on airplane mode
turn the phone off and on again
and then play the file,
watching the same Videos works flawlessly.
So I think something that needs to be online creates a lot of CPU or maybe RAM usage BUT doesnt actually use any data, because then I guess it would pop up extraordinarily on the data usage sheet.