ACM/NetEq: Restructure how post-decode VAD is enabled

webrtc/modules/audio_coding/main/include/audio_coding_module.h

 /*
  *  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 42 matching lines @@
 
   virtual int32_t InFrameType(FrameType frame_type) = 0;
 };
 
 class AudioCodingModule {
  protected:
   AudioCodingModule() {}
 
  public:
   struct Config {
-    Config() : id(0), neteq_config(), clock(Clock::GetRealTimeClock()) {}
+    Config() : id(0), neteq_config(), clock(Clock::GetRealTimeClock()) {
+      // Post-decode VAD is disabled by default in NetEq, however, Audio
+      // Conference Mixer relies on VAD decisions and fails without them.
+      neteq_config.enable_post_decode_vad = true;
+    }
 
     int id;
     NetEq::Config neteq_config;
     Clock* clock;
   };
 
   ///////////////////////////////////////////////////////////////////////////
   // Creation and destruction of a ACM.
   //
   // The second method is used for testing where a simulated clock can be
@@ skipping 675 matching lines @@
   virtual std::vector<uint16_t> GetNackList(
       int64_t round_trip_time_ms) const = 0;
 
   virtual void GetDecodingCallStatistics(
       AudioDecodingCallStats* call_stats) const = 0;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_CODING_MAIN_INCLUDE_AUDIO_CODING_MODULE_H_