Inconsistent refresh rates in RandR and xvidtune

[Tino Keitel]

Hi,

a while ago I noticed that RandR and xvidtune can disagree about the
current refresh rate.

The display in my notebook offers several refresh rates:

   1024x768       50.0 +   60.0*    40.0

First, I'll set it to 60 Hz for sure:

$ xrandr --rate 60 ; xrandr --rate 60

xvidtune shows a mode that also shows 60 Hz when started with the GUI.
On the command line, it looks like this:

$ xvidtune -show
"1024x768"     65.00   1024 1048 1184 1344    768  771  777  806 -hsync
-vsync

Now I set it to 40 Hz using xrandr:

$ xrandr --rate 40
(screen becomes black for a short moment)
$ xvidtune -show
"1024x768"     65.00   1024 1048 1184 1344    768  771  777  806 -hsync
-vsync

As you can see, xvidtune still shows the old mode, and the xvidtune GUI
still shows 60 Hz, but I switched to 40 Hz using xrandr.

Now it gets strange:

$ xrandr -q | grep "1024x768 "
   1024x768       50.0 +   60.0     40.0*
$ xvidtune -show
"1024x768"     43.33   1024 1048 1184 1344    768  771  777  806 -hsync
-vsync

Just running a query changes the xvidtune output.

For me, this has the following impact:

When switching to 60 Hz using xrandr --rate 60, I get stuttering video
in my TV application (MythTV) because the deinterlacer seems to use the
wrong refresh rate.

Other tools that use RandR to change the refresh rate, like the Xfce
display settings, seem to be broken in the same way:

- changing the refresh rate leaves the xvidtune output at the old mode
  and MythTV has stuttering video

- starting the display settings again (which involes a query, to get
  the current mode I guess) leads to xvidtune output for the new mode
  and MythTV has smooth video

I noticed this on a ThinkPad X61s with a i965GM chipset using the Intel
driver version 2.4 and the current 2.5 branch. I don't know if this is
related to the Intel driver or if it is a more generic issue.

Regards,
Tino