Picking resolutions on a Raspberry Pi
Dig through your Raspberry Pi’s boot configuration, and you’ll find the
hdmi_mode variables that control the screen resolution.
Setting these to a value your TV doesn’t support causes your Pi to revert
to a default VGA resolution. So short of trying every possible combination,
how do you figure out which values work for your TV?
Fire up a GUI with
startx and you find the “Monitor Settings” tool under
“Preferences” on the menu. If all you get back is an “Unable to find monitor
information!” error message, you’ll have to resort to the command line.
tvservice with the “-d” flag will spit out a binary file with
information about your TV. You can pipe that file through the
to get something human readable.
/opt/vc/bin/tvservice -d edid.dat
/opt/vc/bin/edidparser edid.dat > edid.txt
There’s a lot of information there about your TV. The interesting lines contain
the word “score”, and describe the mode, resolution, refresh rate, and pixel
clock rates your TV supports. You can
grep the output to figure out if your TV
supports a particular resolution, like 1080p.
cat edid.txt | grep score | grep 1080p
CEA mode (32) 1920x1080p @ 24 Hz...
CEA mode (34) 1920x1080p @ 30 Hz...
Pick the CEA mode by setting the
hdmi_mode variable to “1” in your Pi’s
/boot/config.txt file. Setting it to “2” will pick the DMT mode. The
hdmi_group variable can be set to the number in parenthesis that matches
the resolution you want. In CEA mode, 32 and 34 are both 1080p resolutions.
Once you’ve mode the changes, reboot your Pi to see if they work. Don’t worry if you mess things up. Your Pi will default back to a 640x480 VGA resolution if you pick values your TV doesn’t support.