@airdream a priori je dirai qu'il faut jouer avec les overscans dans le config.txt
# uncomment this if your display has a black border of unused pixels visible
# and your display can output without overscan
#disable_overscan=1
# uncomment the following to adjust overscan. Use positive numbers if console
# goes off screen, and negative if there is too much border
overscan_left=16
overscan_right=16
overscan_top=16
overscan_bottom=16