lavd/avfoundation: Update documentation to mention audio capabilities.

Reviewed-by: Lou Logan <lou@lrcd.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/indevs.texi

@@ -58,28 +58,30 @@ AVFoundation input device.
 AVFoundation is the currently recommended framework by Apple for streamgrabbing on OSX >= 10.7 as well as on iOS.
 The older QTKit framework has been marked deprecated since OSX version 10.7.
 
-The filename passed as input is parsed to contain either a device name or index.
-The device index can also be given by using -video_device_index.
+The filename passed as input is parsed to contain two input streams seperated by ":".
+The first entry selects the video input while the latter selects the audio input @option{"<video>:<audio>"}.
+Each stream can either be specified by the device name or the index.
+The device index can also be given by using @option{-video_device_index <index>} and/or @option{-audio_device_index <index>}, respectively.
 A given device index will override any given device name.
-If the desired device consists of numbers only, use -video_device_index to identify it.
-The default device will be chosen if an empty string  or the device name "default" is given.
-The available devices can be enumerated by using -list_devices.
-The pixel format can be set using -pixel_format.
+If the desired device consists of numbers only, use the device index option to identify it.
+The default device will be chosen if an empty string  or the device name @code{default} is given.
+The available devices can be enumerated by using @option{-list_devices true}.
+The pixel format can be set using @option{-pixel_format <format>}.
 Available formats:
- monob, rgb555be, rgb555le, rgb565be, rgb565le, rgb24, bgr24, 0rgb, bgr0, 0bgr, rgb0,
+@code{monob, rgb555be, rgb555le, rgb565be, rgb565le, rgb24, bgr24, 0rgb, bgr0, 0bgr, rgb0,
  bgr48be, uyvy422, yuva444p, yuva444p16le, yuv444p, yuv422p16, yuv422p10, yuv444p10,
- yuv420p, nv12, yuyv422, gray
+ yuv420p, nv12, yuyv422, gray}
 
 @example
-ffmpeg -f avfoundation -i "0" out.mpg
+ffmpeg -f avfoundation -i "0:0" out.mpg
 @end example
 
 @example
-ffmpeg -f avfoundation -video_device_index 0 -i "" out.mpg
+ffmpeg -f avfoundation -video_device_index 0 -i ":0" out.mpg
 @end example
 
 @example
-ffmpeg -f avfoundation -pixel_format bgr0 -i "default" out.mpg
+ffmpeg -f avfoundation -pixel_format bgr0 -i "default:default" out.mpg
 @end example
 
 @example