Add webcam support on macOS

Closes #29

Change-Id: If09b007e0b9538d3b09266db52060848dd85056c

CHANGELOG.md

@@ -12,6 +12,7 @@
  - Added definition of 8k resolution
  - #34: Now rejects unsupported features in text inputs
  - #30: Fixed cloud upload for VOD
+ - #29: Added webcam support on macOS
 
 
 ## 0.2.0 (2019-10-14)

config_files/input_webcam_config.yaml

@@ -18,7 +18,8 @@
 inputs:
     # The type of input.
   - input_type: webcam
-    # Name of the input device.
+    # Name of the input device.  On Linux, this is a device node path.  On
+    # macOS, this is a device name, typically "default".
     name: /dev/video0
     # The media type.
     media_type: video

streamer/input_configuration.py

@@ -82,8 +82,9 @@ class Input(configuration.Base):
   With input_type set to 'looped_file', this is a path to a file name to be
   looped indefinitely in FFmpeg.
 
-  With input_type set to 'webcam', this is a path to the device node for the
-  webcam.  For example, on Linux, this might be /dev/video0.
+  With input_type set to 'webcam', this is which webcam.  On Linux, this is a
+  path to the device node for the webcam, such as '/dev/video0'.  On macOS, this
+  is a device name, such as 'default'.
 
   With input_type set to 'raw_images', this is a path to a file or pipe
   containing a sequence of raw images.
@@ -314,6 +315,13 @@ def get_input_args(self):
             # up on Linux.
             '-f', 'video4linux2',
         ]
+      elif platform.system() == 'Darwin':  # AKA macOS
+        return [
+            # Webcams on macOS use FFmpeg's avfoundation input format.  With
+            # this, you also have to specify an input framerate, unfortunately.
+            '-f', 'avfoundation',
+            '-framerate', '30',
+        ]
       else:
         assert False, 'Webcams not supported on this platform!'