H.264: Default flags and pulling in openh264 and ffmpeg.

webrtc/build/common.gypi

 # Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 # This file contains common settings for building WebRTC components.
 
@@ skipping 105 matching lines @@
     # enable schannel on windows.
     'use_legacy_ssl_defaults%': 0,
 
     # Determines whether NEON code will be built.
     'build_with_neon%': 0,
 
     # Enable this to use HW H.264 encoder/decoder on iOS/Mac PeerConnections.
     # Enabling this may break interop with Android clients that support H264.
     'use_objc_h264%': 0,
 
+    # Enable this to build H.264 encoder/decoder using third party libraries.
+    # Encoding uses OpenH264 and decoding uses FFmpeg. Because of this, OpenH264
+    # and FFmpeg have to be correctly enabled separately.
+    # - use_openh264=1 is required for OpenH264 targets to be defined.
+    # - ffmpeg_branding=Chrome is one way to support H.264 decoding in FFmpeg.
+    #   FFmpeg can be built with/without H.264 support, see 'ffmpeg_branding'.
+    #   Without it, it compiles but H264DecoderImpl fails to initialize.
+    # CHECK THE OPENH264, FFMPEG AND H.264 LICENSES/PATENTS BEFORE BUILDING.
+    # http://www.openh264.org, https://www.ffmpeg.org/
+    'use_third_party_h264%': 0,  # TODO(hbos): To be used in follow-up CL(s).
+
     'conditions': [
       ['build_with_chromium==1', {
         # Exclude pulse audio on Chromium since its prerequisites don't require
         # pulse audio.
         'include_pulse_audio%': 0,
 
         # Exclude internal ADM since Chromium uses its own IO handling.
         'include_internal_audio_device%': 0,
 
         # Remove tests for Chromium to avoid slowing down GYP generation.
@@ skipping 303 matching lines @@
           # of a more specific macro.
           'defines': [
             'WEBRTC_POSIX',
           ],
         }],
       ],
     },
   }, # target_defaults
 }