[mythtv-users] xrandr selecting invalid resolution/rate

Glen Dragon gdragon at jetcom.org
Tue Jan 1 04:43:52 UTC 2019


I'm seeing an issue where xrandr selects an invalid screen resolution/rate.
It attempts to select 1920x1080 at 71 Hz, which my TV does not like.

I don't know exactly when this problem arose, as this system has been going
for 6 months since power cycle.
This week, it got power cycled, and has been causing all sorts of problems.

It have traced it down to the code thinking that 71 Hz is a valid refresh
rate.  It seems to get this from xrandr.  I don't know how.

xrandr gives me what appears to be reasonable:
dragon at mythfe1:~$ DISPLAY=:0.0 xrandr -q
Screen 0: minimum 8 x 8, current 1920 x 1080, maximum 32767 x 32767
DVI-D-0 disconnected (normal left inverted right x axis y axis)
HDMI-0 connected 1920x1080+0+0 (normal left inverted right x axis y axis)
1872mm x 1053mm
   3840x2160     60.00 +  59.94    50.00    29.97    25.00    23.98
   4096x2160     59.94    50.00    29.97    25.00    24.00    23.98
   2880x576      50.00
   2880x480      59.94
   1920x1080     60.00*   59.94    50.00    29.97    25.00    23.98
60.00    50.04
   1680x1050     59.95
   1600x900      60.00
   1440x900      59.89
   1440x576      50.00
   1440x480      59.94
   1280x1024     75.02    60.02
   1280x800      59.81
   1280x720      60.00    59.94    50.00
   1152x864      75.00
   1024x768      75.03    70.07    60.00
   800x600       75.00    72.19    60.32
   720x576       50.00
   720x480       59.94
   640x480       75.00    72.81    59.94
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)

Here is the verbose output if anyone is interested:
https://pastebin.com/qNYbjJg5

If i try to select 1920x1080 at 60..  I get an error
dragon at mythfe1:~$ DISPLAY=:0.0 xrandr -r 60
Rate 60.00 Hz not available for this size

Using the myth gui i was very surprised to see 50, 64,65,66,67,68,69,70,71
as viable choices.. not 60 hz.. These didn't make any sense to me..
I was able to figure out that they did infact from from xrandr... which i
found (by accident), if i try to select 50 hz:

dragon at mythfe1:~$ DISPLAY=:0.0 xrandr --verbose  -r 50
 SZ:    Pixels          Physical       Refresh
**0   1920 x 1080   ( 487mm x 274mm )  *50   64   65   66   67   68   69
70   71  *
 1   4096 x 2160   (1040mm x 548mm )   51   52   53   54   55   56
 2   3840 x 2160   ( 975mm x 548mm )   57   58   59   60   61
 3   2880 x 576    ( 731mm x 146mm )   62
 4   2880 x 480    ( 731mm x 121mm )   63
 5   1680 x 1050   ( 426mm x 266mm )   72
 6   1600 x 900    ( 406mm x 228mm )   73
 7   1440 x 900    ( 365mm x 228mm )   74
 8   1440 x 576    ( 365mm x 146mm )   75
 9   1440 x 480    ( 365mm x 121mm )   76
 10  1280 x 1024   ( 325mm x 260mm )   77   78
 11  1280 x 800    ( 325mm x 203mm )   79
 12  1280 x 720    ( 325mm x 182mm )   80   81   82
 13  1152 x 864    ( 292mm x 219mm )   83
 14  1024 x 768    ( 260mm x 195mm )   84   85   86
 15   800 x 600    ( 203mm x 152mm )   87   88   89
 16   720 x 576    ( 182mm x 146mm )   90
 17   720 x 480    ( 182mm x 121mm )   91
 18   640 x 480    ( 162mm x 121mm )   92   93   94
 19  2560 x 1600   ( 650mm x 406mm )   95
 20  2560 x 1440   ( 650mm x 365mm )   96
 21  1920 x 1200   ( 487mm x 304mm )   97
 22  1600 x 1200   ( 406mm x 304mm )   98
 23  1366 x 768    ( 346mm x 195mm )   99
Current rotation - normal
Current reflection - none
Rotations possible - normal left inverted right
Reflections possible - X Axis Y Axis
Setting size to 0, rotation to normal
Setting reflection on neither axis

Incidentally if i issue the -r 50 command to xrandr, the TV is happy, and
the tv info displays 1920x1080 60p.

So my options are to turn off xrandr support.. (not ideal, as I use it to
change the resolution when watching 4k stuff [which works fine])..or
manually change the rate with xrandr -r 50 (with an laptop - not WAF
friendly!).

TV is a Samsung 4k (from 2016), video card is nvidia 1050.
I originally found this on ubuntu 16.04.5 with myth master from the
summer.  I don't quite know what changed following the reboot.. maybe
unapplied updates?
I tested today with ubuntu 18.04 with latest myth master, same behavior.

Any suggestions?
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