How do we get better resolution for 360 image in gear vr?

In my Unity project I have a scene of 360 walkthrough in which I use 360 images, but the quality of images are degraded in Gear VR and daydream both. The actual resolution of images is better.

I also tried to improve the image quality by increasing max size and compression property in inspector view of unity, but didn't get any major difference, on the contrary the loading time increased after increasing high quality and size!!!