Audio box flashes on screen {mono/stereo}

Question

a box appears on the upper right side cable/analog *stereo/mono we have digital cable why is my tv showing analog why does the audio switch from mono to stereo {mono being the main one} it doesn't last long but flashes on the screen very often. also my dvd player doesn't have as good a picture as when i had my old tv colors are not good looks, grainy