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

This change avoids calling neteq_->EnableVad() and DisableVad from the
AcmReceiver constructor. Instead, the new member
enable_post_decode_vad is added to NetEq's config struct. It is
disabled by defualt, but ACM sets it to enabled. This preserves the
behavior both of NetEq stand-alone (i.e., in tests) and of ACM.

BUG=webrtc:3520

Review URL: https://codereview.webrtc.org/1425133002

Cr-Commit-Position: refs/heads/master@{#10476}

webrtc/modules/audio_coding/main/acm2/acm_receiver.cc

@@ -128,7 +128,7 @@ AcmReceiver::AcmReceiver(const AudioCodingModule::Config& config)
       audio_buffer_(new int16_t[AudioFrame::kMaxDataSizeSamples]),
       last_audio_buffer_(new int16_t[AudioFrame::kMaxDataSizeSamples]),
       neteq_(NetEq::Create(config.neteq_config)),
-      vad_enabled_(true),
+      vad_enabled_(config.neteq_config.enable_post_decode_vad),
       clock_(config.clock),
       resampled_last_output_frame_(true),
       av_sync_(false),
@@ -136,15 +136,6 @@ AcmReceiver::AcmReceiver(const AudioCodingModule::Config& config)
       missing_packets_sync_stream_(),
       late_packets_sync_stream_() {
   assert(clock_);
-
-  // Make sure we are on the same page as NetEq. Post-decode VAD is disabled by
-  // default in NetEq4, however, Audio Conference Mixer relies on VAD decision
-  // and fails if VAD decision is not provided.
-  if (vad_enabled_)
-    neteq_->EnableVad();
-  else
-    neteq_->DisableVad();
-
   memset(audio_buffer_.get(), 0, AudioFrame::kMaxDataSizeSamples);
   memset(last_audio_buffer_.get(), 0, AudioFrame::kMaxDataSizeSamples);
 }

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

@@ -60,7 +60,11 @@ class 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;

webrtc/modules/audio_coding/neteq/include/neteq.h

@@ -81,6 +81,7 @@ class NetEq {
     Config()
         : sample_rate_hz(16000),
           enable_audio_classifier(false),
+          enable_post_decode_vad(false),
           max_packets_in_buffer(50),
           // |max_delay_ms| has the same effect as calling SetMaximumDelay().
           max_delay_ms(2000),
@@ -92,6 +93,7 @@ class NetEq {
 
     int sample_rate_hz;  // Initial value. Will change with input data.
     bool enable_audio_classifier;
+    bool enable_post_decode_vad;
     size_t max_packets_in_buffer;
     int max_delay_ms;
     BackgroundNoiseMode background_noise_mode;

webrtc/modules/audio_coding/neteq/neteq.cc

@@ -32,6 +32,8 @@ std::string NetEq::Config::ToString() const {
   std::stringstream ss;
   ss << "sample_rate_hz=" << sample_rate_hz << ", enable_audio_classifier="
      << (enable_audio_classifier ? "true" : "false")
+     << ", enable_post_decode_vad="
+     << (enable_post_decode_vad ? "true" : "false")
      << ", max_packets_in_buffer=" << max_packets_in_buffer
      << ", background_noise_mode=" << background_noise_mode
      << ", playout_mode=" << playout_mode

webrtc/modules/audio_coding/neteq/neteq_impl.cc

@@ -112,6 +112,10 @@ NetEqImpl::NetEqImpl(const NetEq::Config& config,
   if (create_components) {
     SetSampleRateAndChannels(fs, 1);  // Default is 1 channel.
   }
+  RTC_DCHECK(!vad_->enabled());
+  if (config.enable_post_decode_vad) {
+    vad_->Enable();
+  }
 }
 
 NetEqImpl::~NetEqImpl() = default;