I have connected my RPi to a television using a HDMI to DVI cable, but the resolution is awful. The font is not sharp, so I need to use a lower resolution. For that, I can run a command like tvservice -e CEA\ 20.

In this answer, Jivings writes that CEA should be used for TVs where DMT is to be used for computer monitors. However, I see both modes being listed in the tvservice output. What is the exact difference and how should I decide what mode to pick?

pi@raspberrypi ~ $ tvservice -s
state 0x120016 [DVI  RGB lim 16:9], 1920x1080 @ 50Hz, interlaced
pi@raspberrypi ~ $ tvservice -m CEA
Group CEA has 6 modes:
           mode 2: 720x480 @ 60Hz 4:3, clock:27MHz progressive 
           mode 5: 1920x1080 @ 60Hz 16:9, clock:74MHz interlaced 
           mode 17: 720x576 @ 50Hz 4:3, clock:27MHz progressive 
           mode 19: 1280x720 @ 50Hz 16:9, clock:74MHz progressive 
  (native) mode 20: 1920x1080 @ 50Hz 16:9, clock:74MHz interlaced 
           mode 21: 720x576 @ 50Hz 4:3, clock:27MHz x2 interlaced 
pi@raspberrypi ~ $ tvservice -m DMT
Group DMT has 2 modes:
           mode 4: 640x480 @ 60Hz 4:3, clock:25MHz progressive
           mode 85: 1280x720 @ 60Hz 16:9, clock:74MHz progressive
  • 2
    In case you're wondering what CEA and DMT stand for, I found that CEA simply stands for the "Consumer Electronics Association", though it's referring to a timing-data extension to Extended Display Identification Data (EDID). DMT stands for Display Monitor Timing, and is part of a VESA standard, as listed here. So in short, they're different ways of specifying display timing. I don't know how to help you pick, though. :) – lindes Dec 9 '13 at 15:42
up vote 13 down vote accepted

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.

In your tvservice output I don't see any overlaps between CEA and DMT modes. If your TV natively supports 50Hz, it would be a bit silly to try to make it work with 60Hz DMT modes.

Unproved: DMT are basically DVI modes and CEA are native HDMI modes, it might be that audio works only for CEA modes.

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