[mythtv-users] "Video Mode not supported" if PC turned on before TV

Ronald Frazier ron at ronfrazier.net
Sat Apr 4 01:24:51 UTC 2009

> If I turn on the TV after the PC has booted, I get a message saying
> "Video Mode Not Supported", but if I turn the PC on after I've already
> turned the TV on, it works!

This is just a guess.

When X starts up, if your TV is on the X driver  is able to query the
TV for supported video modes. What I've noticed is that even if my X
config specifies a format that is invalid, the driver seems to ignore
what the config file says and picks its own chosen resolution from
whatever the TV says is valid. Perhaps the issue is that if the TV is
off (or on another input) it is unable to query the supported modes,
so instead it just assumes that whatever is in the config file is
valid (which it isn't, and thus your TV complains). However, when it's
on and on the proper input, it's able to determine your config is
invalid and automatically fixes the problem.

I don't remember whether or not I had to turn on a special config
option, but if I look in the X log, it enumerates all of the modes
that are supported by my TV. It has a bunch of blocks like this:

(II) NVIDIA(0):   Validating Mode "1920x1080":
(II) NVIDIA(0):     1920 x 1080 @ 60 Hz
(II) NVIDIA(0):     For use as DFP backend.
(II) NVIDIA(0):     Mode Source: EDID
(II) NVIDIA(0):       Pixel Clock      : 148.50 MHz
(II) NVIDIA(0):       HRes, HSyncStart : 1920, 2008
(II) NVIDIA(0):       HSyncEnd, HTotal : 2052, 2200
(II) NVIDIA(0):       VRes, VSyncStart : 1080, 1084
(II) NVIDIA(0):       VSyncEnd, VTotal : 1089, 1125
(II) NVIDIA(0):       H/V Polarity     : +/+
(II) NVIDIA(0):     Mode is valid.

Then (much) further down in the log, it has a bunch of lines like this:

(II) NVIDIA(0): --- Modes in ModePool for SHARP HDMI (DFP-0) ---
(II) NVIDIA(0): "nvidia-auto-select" : 1920 x 1080 @  60.0 Hz  (from: EDID)
(II) NVIDIA(0): "1920x1080"          : 1920 x 1080 @  60.0 Hz  (from: EDID)
(II) NVIDIA(0): "1920x1080_60"       : 1920 x 1080 @  60.0 Hz  (from: EDID)
(II) NVIDIA(0): "1920x1080_65"       : 1920 x 1080 @  65.0 Hz  (from:
X Configuration file ModeLine)

In that last block, the strings in quotes each assign a name to each
of the valid mode blocks. You can use that name in your xorg.conf file
to specify the desired resolution in the Screen Section (Subsection
Modes      "1920x1080_60"

Ronald Frazier Photography - http://www.ronfphoto.com/
Blogging About Photography - http://ronfrazier.blogspot.com/

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