Implement NetEq's CurrentDelay function

This was not implemented before. It returns the current total delay (packet buffer and sync buffer) of NetEq. This is the same information that was already available in NetEqNetworkStatistics::current_buffer_size_ms, that can be obtained through NetEq::NetworkStatistics(). But, since the current delay is a key metric of NetEq, it is convenient to have it available in a simpler way.

R=kwiberg@webrtc.org, minyue@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/51149004

Cr-Commit-Position: refs/heads/master@{#9359}

webrtc/modules/audio_coding/neteq/interface/neteq.h

@@ -210,8 +210,8 @@ class NetEq {
   // Not implemented.
   virtual int TargetDelay() = 0;
 
-  // Not implemented.
+  // Returns the current total delay (packet buffer and sync buffer) in ms.
-  virtual int CurrentDelay() = 0;
+  virtual int CurrentDelayMs() const = 0;
 
   // Sets the playout mode to |mode|.
   // Deprecated. Set the mode in the Config struct passed to the constructor.

webrtc/modules/audio_coding/neteq/neteq_impl.cc

@@ -15,6 +15,7 @@
 
 #include <algorithm>
 
+#include "webrtc/base/checks.h"
 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
 #include "webrtc/modules/audio_coding/codecs/audio_decoder.h"
 #include "webrtc/modules/audio_coding/neteq/accelerate.h"
@@ -291,8 +292,19 @@ int NetEqImpl::TargetDelay() {
   return kNotImplemented;
 }
 
-int NetEqImpl::CurrentDelay() {
+int NetEqImpl::CurrentDelayMs() const {
-  return kNotImplemented;
+  CriticalSectionScoped lock(crit_sect_.get());
+  if (fs_hz_ == 0)
+    return 0;
+  // Sum up the samples in the packet buffer with the future length of the sync
+  // buffer, and divide the sum by the sample rate.
+  const int delay_samples =
+      packet_buffer_->NumSamplesInBuffer(decoder_database_.get(),
+                                         decoder_frame_length_) +
+      static_cast<int>(sync_buffer_->FutureLength());
+  // The division below will truncate.
+  const int delay_ms = delay_samples / rtc::CheckedDivExact(fs_hz_, 1000);
+  return delay_ms;
 }
 
 // Deprecated.

webrtc/modules/audio_coding/neteq/neteq_impl.h

@@ -138,7 +138,7 @@ class NetEqImpl : public webrtc::NetEq {
 
   int TargetDelay() override;
 
-  int CurrentDelay() override;
+  int CurrentDelayMs() const override;
 
   // Sets the playout mode to |mode|.
   // Deprecated.

webrtc/modules/audio_coding/neteq/neteq_network_stats_unittest.cc

@@ -170,6 +170,9 @@ struct NetEqNetworkStatsCheck {
     CHECK_NETEQ_NETWORK_STATS(added_zero_samples);
 
 #undef CHECK_NETEQ_NETWORK_STATS
+
+    // Compare with CurrentDelay, which should be identical.
+    EXPECT_EQ(stats.current_buffer_size_ms, neteq()->CurrentDelayMs());
   }
 
   void RunTest(int num_loops, NetEqNetworkStatsCheck expects) {

webrtc/modules/audio_coding/neteq/neteq_unittest.cc

@@ -404,6 +404,8 @@ void NetEqDecodingTest::DecodeAndCompare(const std::string& rtp_file,
       ASSERT_EQ(0, neteq_->NetworkStatistics(&network_stats));
       ASSERT_NO_FATAL_FAILURE(
           network_stat_files.ProcessReference(network_stats));
+      // Compare with CurrentDelay, which should be identical.
+      EXPECT_EQ(network_stats.current_buffer_size_ms, neteq_->CurrentDelayMs());
 
       // Process RTCPstat.
       RtcpStatistics rtcp_stats;