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  1.   1.  ffmpeg and VirtualBox
    1.   1.1  800x600
    2.   1.2  1024x768
    3.   1.3  1280x960
  2.   2.  xwininfo
    1.   2.1  on the web

1.  ffmpeg and VirtualBox

I use to start VirtualBox on the upper right corner of my screen (HD:1920x1080). When launching the openSUSE dvd, we can't choose the screen definition, it's always 800x600. After the first boot it changes, usually for 1024x768 (no 16x9 available - see Vesa definitions).

If the install is stopped (on a menu, for example, move the cursor on the boot menu to stop), and then re-positionned, it keeps it's place next boot.

1.1  800x600

On first boot, the VirtualBox screen, as reported by xwininfo -frame (see below) is:

Corners: +1116+23 -4+23 -4-416 +1116-416
-geometry 800x641-4+23

From this we can guess VirtualBox decoration size:

0 (zero) on left and right (we still have 800 pixels, the screen full size), 641-600=41 pixels. We have to guess what is the part of the upper ribbon (menus) and the lower (information icons). Seems to be half for each, so I use 43 pixels offset for ffmpeg

This gives for the first windows:

/usr/bin/ffmpeg -f x11grab -r 25 -s 800x600 -i :0.0+1116,43 -target pal-dvd /local/data/temp-data/114.mpg

 -r 25

is for frame number per second

1.2  1024x768

for second size windows (also upper right aligned)

Corners: +892+23 -4+23 -4-248 +892-248 -geometry 1024x809-4+23
/usr/bin/ffmpeg -f x11grab -r 25 -s 1024x768 -i :0.0+892,43 -target pal-dvd /local/data/temp-data/114.mpg

1.3  1280x960

Last part 1280x960

Corners: +636+23 -4+23 -4-56 +636-56
-geometry 1280x1001-4+23

/usr/bin/ffmpeg -f x11grab -r 25 -s 1280x960 -i :0.0+636,43 -target pal-dvd /local/data/temp-data/114.mpg

2.  xwininfo

Xwindows measurements are not that easy to understand.

Corners are counted as upper left (1), upper right (2), lower right (3), lower left (4).

The numbers are pixel (option -metric add mm), a "+" in front means "from left", a "-", "from right"

xwininfo -frame
Corners: +1228+628 -0+628 -0-0 +1228-0
geometry 692x452-0-0

means (here Konsole):

The windows is 692x452 pixels, including Kde decorations. The lower right corner is on the lower right position of the screen (-0-0). The upper left corner is at 1228 pixels from the left limit of the screen (1228+692=1920, I have a HD screen). Upper right corner is (-0) just on the right limit of ther screen, and at (+628) 628 pixels from the upper limit of the screen (1080-628=452).

Without the frame option, xwininfo gives the windows size without the kde decoration:

Corners: +1232+651 -4+651 -4-4 +1232-4
-geometry 684x425-0-0

You can see than kde deco is 4 pix wide on bottom, left and right (-4-4), the upper ribbon is 23 pixels height (651-628=23). This do not take account of the proper application decoration.

2.1  on the web

ffmpeg -f x11grab -s 1280x1024 -r 10 -i :0.0 -f alsa -i pulse -sameq -r 30 test.mpg