This will show how to force output of 720p to a TV
Configure the xorg.conf
Section "ServerLayout"
Identifier "Default Layout"
Screen "Default Screen" 0 0
EndSection
Section "Module"
Load "glx"
EndSection
Section "Monitor"
Identifier "CRT-0"
HorizSync 31.0 - 69.0
VertRefresh 59.0 - 86.0
Modeline "1280x768_60" 79.50 1280 1344 1472 1664 768 771 781 798 -hsync +vsync
Option "PreferredMode" "1280x768_60"
Option "DPMS"
EndSection
Section "Device"
Identifier "NVIDIA GPU GeForce 9400"
Driver "nvidia"
Option "NoLogo" "False"
# Option "TripleBuffer "True"
Option "IgnoreEDID" "True"
Option "UseEDID" "False"
Option "UseEDIDFreqs" "False"
Option "UseEDIDDpi" "False"
Option "RegistryDwords" "PowerMizerEnable=0x1; PerfLevelSrc=0x3322; PowerMizerDefaultAC=0x1"
EndSection
Section "Extensions"
Option "Composite" "Disable"
EndSection
Section "Screen"
Identifier "Default Screen"
Device "NVIDIA GPU GeForce 9400"
Monitor "CRT-0"
DefaultDepth 24
SubSection "Display"
Depth 24
Option "MetaModes" "1280x768_60"
# Modes "1280