Update the BWE when the network route changes.

webrtc/modules/congestion_controller/congestion_controller.cc

Index: webrtc/modules/congestion_controller/congestion_controller.cc
diff --git a/webrtc/modules/congestion_controller/congestion_controller.cc b/webrtc/modules/congestion_controller/congestion_controller.cc
index 5767448a5f7bf711a24ef214ea47d5f5cac18f20..4e88fe634a37e808789e5b5171c0ae24f0dc1d09 100644
--- a/webrtc/modules/congestion_controller/congestion_controller.cc
+++ b/webrtc/modules/congestion_controller/congestion_controller.cc
@@ -32,6 +32,22 @@ namespace {
 
 static const uint32_t kTimeOffsetSwitchThreshold = 30;
 
+// Makes sure that the bitrate and the min, max values are in valid range.
+static void ClampBitrates(int* bitrate_bps,
+                          int* min_bitrate_bps,
+                          int* max_bitrate_bps) {
+  // TODO(holmer): We should make sure the default bitrates are set to 10 kbps,
+  // and that we don't try to set the min bitrate to 0 from any applications.
+  // The congestion controller should allow a min bitrate of 0.
+  const int kMinBitrateBps = 10000;
+  if (*min_bitrate_bps < kMinBitrateBps)
+    *min_bitrate_bps = kMinBitrateBps;
+  if (*max_bitrate_bps > 0)
+    *max_bitrate_bps = std::max(*min_bitrate_bps, *max_bitrate_bps);
+  if (*bitrate_bps > 0)
+    *bitrate_bps = std::max(*min_bitrate_bps, *bitrate_bps);
+}
+
 class WrappingBitrateEstimator : public RemoteBitrateEstimator {
  public:
   WrappingBitrateEstimator(RemoteBitrateObserver* observer, Clock* clock)
@@ -212,21 +228,10 @@ void CongestionController::Init() {
       min_bitrate_bps_);
 }
 
-
 void CongestionController::SetBweBitrates(int min_bitrate_bps,
                                           int start_bitrate_bps,
                                           int max_bitrate_bps) {
-  // TODO(holmer): We should make sure the default bitrates are set to 10 kbps,
-  // and that we don't try to set the min bitrate to 0 from any applications.
-  // The congestion controller should allow a min bitrate of 0.
-  const int kMinBitrateBps = 10000;
-  if (min_bitrate_bps < kMinBitrateBps)
-    min_bitrate_bps = kMinBitrateBps;
-  if (max_bitrate_bps > 0)
-    max_bitrate_bps = std::max(min_bitrate_bps, max_bitrate_bps);
-  if (start_bitrate_bps > 0)
-    start_bitrate_bps = std::max(min_bitrate_bps, start_bitrate_bps);
-
+  ClampBitrates(&start_bitrate_bps, &min_bitrate_bps, &max_bitrate_bps);
   bitrate_controller_->SetBitrates(start_bitrate_bps,
                                    min_bitrate_bps,
                                    max_bitrate_bps);
@@ -239,6 +244,24 @@ void CongestionController::SetBweBitrates(int min_bitrate_bps,
   MaybeTriggerOnNetworkChanged();
 }
 
+void CongestionController::ResetBweAndBitrates(int bitrate_bps,
+                                               int min_bitrate_bps,
+                                               int max_bitrate_bps) {
+  ClampBitrates(&bitrate_bps, &min_bitrate_bps, &max_bitrate_bps);
+  bitrate_controller_->ResetBitrates(bitrate_bps, min_bitrate_bps,

[stefan-webrtc, 2016/05/31 17:27:49]

I wonder if we instead should simply recreate the bitrate controller object to
avoid having a new method. WDYT? Sorry for not bringing this up earlier.

[honghaiz3, 2016/06/01 02:17:34]

No we cannot because some of the objects in congestion controller is used by
other objects. 
For example, the pacer is used by AudioSendStream (and probably videosendstream
too). 
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/webrtc...
Plus, the pacer (an object in CongestionController) probably should not be
replaced because it contains the pending packet queue. 

[stefan-webrtc, 2016/06/01 07:38:36]

I was referring to bitrate_controller_ and not congestion controller. I think it
should be possible to do if we remove the GetBitrateController() method. Feel
free to add a TODO instead if it turns out to be too much work.

[honghaiz3, 2016/06/01 16:54:10]

Ah sorry that I mis-read it. 
It had similar issues because the pointer was used by VideoSendStream here:
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/webrtc...
There the created bandwidth observer contains a pointer to the
bitrate_controller_.
Add a TODO

+                                     max_bitrate_bps);
+  min_bitrate_bps_ = min_bitrate_bps;
+  if (remote_bitrate_estimator_)
+    remote_bitrate_estimator_->SetMinBitrate(min_bitrate_bps);

[stefan-webrtc, 2016/05/31 17:27:49]

Here too, shouldn't we recreate this object as well?

[honghaiz3, 2016/06/01 02:17:34]

Cannot for the same reason. 
It was used by the videoreceivestream. 
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/webrtc...

[stefan-webrtc, 2016/06/01 07:38:36]

I see, could you add a TODO which says "Recreate this object once the remote
bitrate estimator no longer is exposed outside CongestionController."

[honghaiz3, 2016/06/01 16:54:10]

Done.

+
+  RemoteBitrateEstimator* rbe =
+      new RemoteBitrateEstimatorAbsSendTime(&transport_feedback_adapter_);
+  transport_feedback_adapter_.SetBitrateEstimator(rbe);
+  rbe->SetMinBitrate(min_bitrate_bps);
+  // TODO(holmer): Trigger a new probe once mid-call probing is implemented.
+  MaybeTriggerOnNetworkChanged();
+}
+
 BitrateController* CongestionController::GetBitrateController() const {
   return bitrate_controller_.get();
 }