x11grab: add show_region AVOption.

Draw the current grabbing region for indication.

Signed-off-by: Yu-Jie Lin <livibetter@gmail.com>
Signed-off-by: Anton Khirnov <anton@khirnov.net>

2 files changed, 32 insertions, 0 deletions

diff --git a/doc/ffmpeg.texi b/doc/ffmpeg.texi
index 8d3968dbf2..f3a4689d6c 100644
--- a/doc/ffmpeg.texi
+++ b/doc/ffmpeg.texi
@@ -916,6 +916,19 @@ ffmpeg -f x11grab -follow_mouse 100 -s cif -r 25 -i :0.0 /tmp/out.mpg
 Only follows when mouse pointer reaches within 100 pixels to the edge of
 region.
 
+@example
+ffmpeg -f x11grab -show_region 1 -s cif -r 25 -i :0.0+10,20 /tmp/out.mpg
+@end example
+
+The grabbing region will be indicated on screen.
+
+@example
+ffmpeg -f x11grab -follow_mouse centered -show_region 1 -s cif -r 25 -i :0.0 /tmp/out.mpg
+@end example
+
+The grabbing region indication will follow the mouse pointer.
+
+
 @section Video and Audio file format conversion
 
 Any supported file format and protocol can serve as input to ffmpeg:
diff --git a/doc/indevs.texi b/doc/indevs.texi
index aa001cdb63..fa21c099d5 100644
--- a/doc/indevs.texi
+++ b/doc/indevs.texi
@@ -271,4 +271,23 @@ ffmpeg -f x11grab -follow_mouse centered -r 25 -s cif -i :0.0 out.mpg
 ffmpeg -f x11grab -follow_mouse 100 -r 25 -s cif -i :0.0 out.mpg
 @end example
 
+@subsection @var{show_region} AVOption
+
+The syntax is:
+@example
+-show_region 1
+@end example
+
+If @var{show_region} AVOption is specified with @var{1}, then the grabbing
+region will be indicated on screen. With this option, it's easy to know what is
+being grabbed if only a portion of the screen is grabbed.
+
+For example:
+@example
+ffmpeg -f x11grab -show_region 1 -r 25 -s cif -i :0.0+10,20 out.mpg
+
+# With follow_mouse
+ffmpeg -f x11grab -follow_mouse centered -show_region 1  -r 25 -s cif -i :0.0 out.mpg
+@end example
+
 @c man end INPUT DEVICES