avdevice: add decklink input support

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/indevs.texi

@@ -922,4 +922,58 @@ Use the MIT-SHM extension for shared memory. Default value is @code{1}.
 It may be necessary to disable it for remote displays.
 @end table
 
+@section decklink
+
+The decklink input device provides capture capabilities for Blackmagic
+DeckLink devices.
+
+To enable this input device, you need the Blackmagic DeckLink SDK and you
+need to configure with the appropriate @code{--extra-cflags}
+and @code{--extra-ldflags}.
+On Windows, you need to run the IDL files through @command{widl}.
+
+DeckLink is very picky about the formats it supports. Pixel format is always
+uyvy422, framerate and video size must be determined for your device with
+@command{-list_formats 1}. Audio sample rate is always 48 kHz and the number
+of channels currently is limited to 2 (stereo).
+
+@subsection Options
+
+@table @option
+
+@item list_devices
+If set to @option{true}, print a list of devices and exit.
+Defaults to @option{false}.
+
+@item list_formats
+If set to @option{true}, print a list of supported formats and exit.
+Defaults to @option{false}.
+
+@end table
+
+@subsection Examples
+
+@itemize
+
+@item
+List input devices:
+@example
+ffmpeg -f decklink -list_devices 1 -i dummy
+@end example
+
+@item
+List supported formats:
+@example
+ffmpeg -f decklink -list_formats 1 -i 'Intensity Pro'
+@end example
+
+@item
+Capture video clip at 1080i50 (format 11):
+@example
+ffmpeg -f decklink -i 'Intensity Pro@@11' -acodec copy -vcodec copy output.avi
+@end example
+
+@end itemize
+
+
 @c man end INPUT DEVICES