This may not apply to you but my phone takes 4160x2336 (9.7MP) 3.0MB images, I always resize the images to 1923x1080 (2.1MP) 265.3kB. I always try to reduce the images file size below 1.0MB before I drag-drop onto the post I'm writing. This is a habit I've stuck to since some STEEM Dapps have a image size limit.
Sorry can't help you with D.tube, I don't use it.
Thank you so very much @kiwibloke.
I had to do that too with my images too but that was with one of my phones.