Using AudioOption to enable audio network adaptor.

webrtc/api/call/audio_send_stream.h

Index: webrtc/api/call/audio_send_stream.h
diff --git a/webrtc/api/call/audio_send_stream.h b/webrtc/api/call/audio_send_stream.h
index b309f7a221c6c07298f0a13133dfbb2389a5b746..f7b13cbd6b0e1afbecc21d6314ebf89af7e299f2 100644
--- a/webrtc/api/call/audio_send_stream.h
+++ b/webrtc/api/call/audio_send_stream.h
@@ -111,6 +111,13 @@ class AudioSendStream {
 
   virtual Stats GetStats() const = 0;
 
+  virtual bool EnableAudioNetworkAdaptor(const std::string& config_string) = 0;

[the sun, 2016/10/06 08:03:46]

One of the major ideas with the new API is to have as few state-mutating
functions as possible, and instead move all of these types of settings to the
Config struct, so that they are only ever initialized in the constructor. When
settings change (because e.g. an Offer-Answer exchange), streams are instead
*recreated*.

That being said, IIUC you're also adding the information to
AudioCodingModule::Config. Since there is an ACM per VoE Channel (and a VoE
Channel per send stream), does that mean you do not need any of these API calls
at all, but that it is enough to propagate the information that path?

[minyue-webrtc, 2016/10/06 08:16:53]

Actually, this is audio network adaptor is a codec feature. It belongs to
DTX/FEC etc. But differently, it is set by AudioOption instead of SDP. I see
that SetOption only touches call_config_, and therefore, I tried to reuse
call_config_ (call_config_.acm_config in particular), but this is not necessary.

What makes it cumbersome is that I need to call to
Channel::EnableAudioNetworkAdaptor in SetSendCodec, which makes it similar to
many VoECodec functions. As long as SetSendCodec is called outside Ctor, I
cannot find a good way to avoid adding these APIs.

+
+  virtual void DisableAudioNetworkAdaptor() = 0;
+
+  virtual void SetReceiverFrameLengthRange(int min_frame_length_ms,
+                                           int max_frame_length_ms) = 0;
+
  protected:
   virtual ~AudioSendStream() {}
 };