Added a flag to AudioCodecSpec to indicate adaptive bitrate support.

webrtc/modules/audio_coding/codecs/builtin_audio_decoder_factory.cc

 /*
  *  Copyright (c) 2016 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.
  */
 
@@ skipping 156 matching lines @@
        } else {
          return false;
        }
      }},
 #endif
 };
 
 class BuiltinAudioDecoderFactory : public AudioDecoderFactory {
  public:
   std::vector<AudioCodecSpec> GetSupportedDecoders() override {
-    static std::vector<AudioCodecSpec> specs = {
+    // Although this looks a bit strange, it means specs need only be initalized
+    // once, and that that initialization is thread-safe.
+    static std::vector<AudioCodecSpec> specs =
+        []{
+          std::vector<AudioCodecSpec> specs;
 #ifdef WEBRTC_CODEC_OPUS
-      { { "opus", 48000, 2, {
-            {"minptime", "10" },
-            {"useinbandfec", "1" }
-          }
-        }, false
-      },
+          AudioCodecSpec opus({"opus", 48000, 2, {
+                                 {"minptime", "10"},
+                                 {"useinbandfec", "1"}
+                               }});
+          opus.allow_comfort_noise = false;
+          opus.supports_network_adaption = true;
+          specs.push_back(opus);
 #endif
 #if (defined(WEBRTC_CODEC_ISAC) || defined(WEBRTC_CODEC_ISACFX))
-      {{"isac", 16000, 1}, true},
+          specs.push_back(AudioCodecSpec({"isac", 16000, 1}));
 #endif
 #if (defined(WEBRTC_CODEC_ISAC))
-      {{"isac", 32000, 1}, true},
+          specs.push_back(AudioCodecSpec({"isac", 32000, 1}));
 #endif
 #ifdef WEBRTC_CODEC_G722
-      {{"G722", 8000, 1}, true},
+          specs.push_back(AudioCodecSpec({"G722", 8000, 1}));
 #endif
 #ifdef WEBRTC_CODEC_ILBC
-      {{"iLBC", 8000, 1}, true},
+          specs.push_back(AudioCodecSpec({"iLBC", 8000, 1}));
 #endif
-      {{"PCMU", 8000, 1}, true},
-      {{"PCMA", 8000, 1}, true}
-    };
-
+          specs.push_back(AudioCodecSpec({"PCMU", 8000, 1}));
+          specs.push_back(AudioCodecSpec({"PCMA", 8000, 1}));
+          return specs;
+        }();
     return specs;
   }
 
   bool IsSupportedDecoder(const SdpAudioFormat& format) override {
     for (const auto& dc : decoder_constructors) {
       if (STR_CASE_CMP(format.name.c_str(), dc.name) == 0) {
         return dc.constructor(format, nullptr);
       }
     }
     return false;
@@ skipping 21 matching lines @@
 };
 
 }  // namespace
 
 rtc::scoped_refptr<AudioDecoderFactory> CreateBuiltinAudioDecoderFactory() {
   return rtc::scoped_refptr<AudioDecoderFactory>(
       new rtc::RefCountedObject<BuiltinAudioDecoderFactory>);
 }
 
 }  // namespace webrtc