Implement recording to Matroska files.
The format to use is determined by the option -F/--record-format if set,
or by the file extension (".mp4" or ".mkv").
It is very convenient when I play mobile game and watch video at the
same time.
Tested on Linux mint Cinnamon as well as Windows 10.
Signed-off-by: Yu-Chen Lin <npes87184@gmail.com>
Accept a parameter to limit the video size.
For instance, with "-m 960", the great side of the video will be scaled
down to 960 (if necessary), while the other side will be scaled down so
that the aspect ratio is preserved. Both dimensions must be a multiple
of 8, so black bands might be added, and the mouse positions must be
computed accordingly.
