NetEq: Implement Expand::Muted

Adding a new method to the Expand class, which will answer the question
whether an ongoing expansion has been faded down to zero
amplitude (i.e., been muted). Also adding a test.

This new functionality will be used in CLs to follow.

BUG=webrtc:5608
NOTRY=True

Review-Url: https://codereview.webrtc.org/1967473004
Cr-Commit-Position: refs/heads/master@{#12672}

webrtc/modules/audio_coding/neteq/expand.cc

@@ -327,6 +327,17 @@ void Expand::SetParametersForMergeAfterExpand() {
   stop_muting_ = true;
 }
 
+bool Expand::Muted() const {
+  if (first_expand_ || stop_muting_)
+    return false;
+  RTC_DCHECK(channel_parameters_);
+  for (size_t ch = 0; ch < num_channels_; ++ch) {
+    if (channel_parameters_[ch].mute_factor != 0)
+      return false;
+  }
+  return true;
+}
+
 size_t Expand::overlap_length() const {
   return overlap_length_;
 }

webrtc/modules/audio_coding/neteq/expand.h

@@ -62,6 +62,10 @@ class Expand {
     return channel_parameters_[channel].mute_factor;
   }
 
+  // Returns true if expansion has been faded down to zero amplitude (for all
+  // channels); false otherwise.
+  bool Muted() const;
+
   // Accessors and mutators.
   virtual size_t overlap_length() const;
   size_t max_lag() const { return max_lag_; }

webrtc/modules/audio_coding/neteq/expand_unittest.cc

@@ -169,6 +169,37 @@ TEST_F(ExpandTest, CheckOutageStatsAfterReset) {
             statistics_.last_outage_duration_ms());
 }
 
+namespace {
+// Runs expand until Muted() returns true. Times out after 1000 calls.
+void ExpandUntilMuted(size_t num_channels, Expand* expand) {
+  EXPECT_FALSE(expand->Muted()) << "Instance is muted from the start";
+  AudioMultiVector output(num_channels);
+  int num_calls = 0;
+  while (!expand->Muted()) {
+    ASSERT_LT(num_calls++, 1000) << "Test timed out";
+    EXPECT_EQ(0, expand->Process(&output));
+  }
+}
+}  // namespace
+
+// Verifies that Muted() returns true after a long expand period. Also verifies
+// that Muted() is reset to false after calling Reset(),
+// SetParametersForMergeAfterExpand() and SetParametersForNormalAfterExpand().
+TEST_F(ExpandTest, Muted) {
+  ExpandUntilMuted(num_channels_, &expand_);
+  expand_.Reset();
+  EXPECT_FALSE(expand_.Muted());  // Should be back to unmuted.
+
+  ExpandUntilMuted(num_channels_, &expand_);
+  expand_.SetParametersForMergeAfterExpand();
+  EXPECT_FALSE(expand_.Muted());  // Should be back to unmuted.
+
+  expand_.Reset();  // Must reset in order to start a new expand period.
+  ExpandUntilMuted(num_channels_, &expand_);
+  expand_.SetParametersForNormalAfterExpand();
+  EXPECT_FALSE(expand_.Muted());  // Should be back to unmuted.
+}
+
 // TODO(hlundin): Write more tests.
 
 }  // namespace webrtc