video only takes a quarter of the screen

[rikardo1979]

your problem lies in EDID detection which cause the issue.
To overcome this you may try change the HDMI cable(my own experience as I had a cable which wasnt cheap but caused the issue with CEC) or you can try force the HDMI mode to native resolution of your screen

you can try force EDID ignore

Code:

hdmi_ignore_edid=0xa5000080

you can also try force HDMI

Code:

hdmi_force_hotplug=1

or find out details of your HDMI device and use
hdmi_group and hdmi_mode with appropriate values to force the parameters