Pass time constant to bwe smoothing filter.

webrtc/voice_engine/channel_proxy.h

Index: webrtc/voice_engine/channel_proxy.h
diff --git a/webrtc/voice_engine/channel_proxy.h b/webrtc/voice_engine/channel_proxy.h
index 182e2524b56ffa535ccee1419ab6a67358a1f7a3..b73201b5f912557eaad4a8e950599aaba3a464f7 100644
--- a/webrtc/voice_engine/channel_proxy.h
+++ b/webrtc/voice_engine/channel_proxy.h
@@ -71,7 +71,8 @@ class ChannelProxy {
   virtual uint32_t GetDelayEstimate() const;
   virtual bool SetSendTelephoneEventPayloadType(int payload_type);
   virtual bool SendTelephoneEventOutband(int event, int duration_ms);
-  virtual void SetBitrate(int bitrate_bps);
+  virtual void SetBitrate(int bitrate_bps,
+                          rtc::Optional<int64_t> probing_interval_ms);

[michaelt, 2016/11/24 13:47:18]

I pass here rtc::Optional<int64_t>, since we should Ignore the value, passed as
initial value to the encoder, in the smoothing filter. Since we have no
information about the probing interval at this point. Passing zero, here would
lead to the skip of the init phase of the filter. 

[stefan-webrtc, 2016/11/24 13:52:40]

Hm, why don't we pass optional all the way from the probing estimator? Do we
ever use the default value in the beginning before we have a real estimate?

[michaelt, 2016/11/24 13:59:37]

When the start BWE is lower than the actual BW, we would use the default
interval till we had the first drop. And since it mad more sense to me to define
the default in the estimator I choose this impl.   

[stefan-webrtc, 2016/11/24 14:07:11]

Ok, I guess my question is, why does it even have to be optional here? Does it
ever get called with it not being set? I see that it's called from
VoECodec::SetBitRate(), but that function is in turn never being called...

https://cs.chromium.org/chromium/src/third_party/webrtc/voice_engine/voe_code...

[michaelt, 2016/11/24 15:13:46]

I made it Optional because of VoECodec::SetBitRate() :).
You are right this function is never called. So I think a can safely remove the
Optional. 

[stefan-webrtc, 2016/11/24 15:19:02]

I would remove that method too. Maybe that should be done separately. I leave it
to solenberg and minyue to decide

   virtual void SetSink(std::unique_ptr<AudioSinkInterface> sink);
   virtual void SetInputMute(bool muted);
   virtual void RegisterExternalTransport(Transport* transport);