Raspberry Pi infos

Having troubles with your tv screen ?

1) Run the following commands to know what's going on with your screen and the raspberry pi

tvservice -s (or --status) # get HDMI status : will tell you what your current HDMI mode is.
tvservice -m CEA (or --modes=CEA) # get supported modes for CEA : will tell you the "CEA modes" available. (hdmi group 1)
tvservice -m DMT (or --modes=DMT) # get supported modes for DMT : will tell you the "DMT modes" available. (hdmi group 2)

CEA vs DMT

• CEA modes are intended for TV, they include plenty of interlaced and progressive modes,

  usually with 25/50/100Hz (PAL) or 30/60/120Hz (NTSC)

  frame rates and TV resolutions of 288/480/576/720/1080 scan lines.

• DMT modes are intended for computer monitors, therefore there are none of the interlaced modes,

  the resolutions are 640/720/800/1024/1280 and

  the frame rates are compatible with the computer monitors, something like 60/70/75/80/85/120Hz.

/boot/config.sys

By modifying this file, you can hard code display data for the raspberry pi.

sudo nano /boot/config.sys

For example, you can change :

sdtv_aspect=3

in order to have 16:9 aspect and

hdmi_safe=1.

to force getting a picture on HDMI for a default "safe" mode.

Sources

• https://www.raspberrypi.org/forums/viewtopic.php?t=72871

• https://www.raspberrypi.org/forums/viewtopic.php?t=52309

• https://raspberrypi.stackexchange.com/questions/7332/what-is-the-difference-between-cea-and-dmt

• https://github.com/raspberrypi/userland/tree/master/host_applications/linux/apps/tvservice