Base A/V synchronization on sync_labels.

webrtc/video_engine/vie_sync_module.cc

 /*
  *  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.
  */
 
@@ skipping 49 matching lines @@
 }
 
 ViESyncModule::~ViESyncModule() {
 }
 
 int ViESyncModule::ConfigureSync(int voe_channel_id,
                                  VoEVideoSync* voe_sync_interface,
                                  RtpRtcp* video_rtcp_module,
                                  RtpReceiver* video_receiver) {
   CriticalSectionScoped cs(data_cs_.get());
+  // Prevent expensive no-ops.
+  if (voe_channel_id_ == voe_channel_id &&
+      voe_sync_interface_ == voe_sync_interface &&
+      video_receiver_ == video_receiver &&
+      video_rtp_rtcp_ == video_rtcp_module) {
+    return 0;
+  }
   voe_channel_id_ = voe_channel_id;
   voe_sync_interface_ = voe_sync_interface;
   video_receiver_ = video_receiver;
   video_rtp_rtcp_ = video_rtcp_module;
   sync_.reset(
       new StreamSynchronization(video_rtp_rtcp_->SSRC(), voe_channel_id));
 
   if (!voe_sync_interface) {
     voe_channel_id_ = -1;
     if (voe_channel_id >= 0) {
@@ skipping 92 matching lines @@
   }
   sync_->SetTargetBufferingDelay(target_delay_ms);
   // Setting initial playout delay to voice engine (video engine is updated via
   // the VCM interface).
   voe_sync_interface_->SetInitialPlayoutDelay(voe_channel_id_,
                                               target_delay_ms);
   return 0;
 }
 
 }  // namespace webrtc