Pull out the PostFilter to its own NonlinearBeamformer API

webrtc/modules/audio_processing/audio_processing_impl.cc

Index: webrtc/modules/audio_processing/audio_processing_impl.cc
diff --git a/webrtc/modules/audio_processing/audio_processing_impl.cc b/webrtc/modules/audio_processing/audio_processing_impl.cc
index d89cc339315c5bf6b76cda4334eff5dbe8137121..f417a856da5d70db046404e9c841a3968d81593f 100644
--- a/webrtc/modules/audio_processing/audio_processing_impl.cc
+++ b/webrtc/modules/audio_processing/audio_processing_impl.cc
@@ -127,10 +127,10 @@ struct AudioProcessingImpl::ApmPublicSubmodules {
 };
 
 struct AudioProcessingImpl::ApmPrivateSubmodules {
-  explicit ApmPrivateSubmodules(Beamformer<float>* beamformer)
+  explicit ApmPrivateSubmodules(NonlinearBeamformer* beamformer)
       : beamformer(beamformer) {}
   // Accessed internally from capture or during initialization
-  std::unique_ptr<Beamformer<float>> beamformer;
+  std::unique_ptr<NonlinearBeamformer> beamformer;
   std::unique_ptr<AgcManagerDirect> agc_manager;
 };
 
@@ -144,7 +144,7 @@ AudioProcessing* AudioProcessing::Create(const Config& config) {
 }
 
 AudioProcessing* AudioProcessing::Create(const Config& config,
-                                         Beamformer<float>* beamformer) {
+                                         NonlinearBeamformer* beamformer) {
   AudioProcessingImpl* apm = new AudioProcessingImpl(config, beamformer);
   if (apm->Initialize() != kNoError) {
     delete apm;
@@ -158,7 +158,7 @@ AudioProcessingImpl::AudioProcessingImpl(const Config& config)
     : AudioProcessingImpl(config, nullptr) {}
 
 AudioProcessingImpl::AudioProcessingImpl(const Config& config,
-                                         Beamformer<float>* beamformer)
+                                         NonlinearBeamformer* beamformer)
     : public_submodules_(new ApmPublicSubmodules()),
       private_submodules_(new ApmPrivateSubmodules(beamformer)),
       constants_(config.Get<ExperimentalAgc>().startup_min_volume,
@@ -680,8 +680,8 @@ int AudioProcessingImpl::ProcessStreamLocked() {
   }
 
   if (capture_nonlocked_.beamformer_enabled) {
-    private_submodules_->beamformer->ProcessChunk(*ca->split_data_f(),
-                                                  ca->split_data_f());
+    private_submodules_->beamformer->AnalyzeChunk(*ca->split_data_f());

[peah-webrtc, 2016/06/08 12:04:55]

What has changed here, is that now all the downmixing is done by the
set_num_channels call, in contrast to that before the downmixing was done inside
the beamformer, but the set_num_channels call was needed to correct for the new
number of channels? Is that correct?

[aluebs-webrtc, 2016/06/09 02:11:46]

What do you mean with downmixing? Before there was a frequency domain fixed
delay and sum beamformer and then the number of channels was corrected in the
AudioBuffer. Now all channels except the first one are discarded.

[peah-webrtc, 2016/06/09 09:36:30]

By downmixing I mean going from 2 to 1 channel, so discarding the leftmost
channel definitely counts as that.

[aluebs-webrtc, 2016/06/09 19:21:42]

Personally I find "downmixing" to have a blending implication. But acknowledged.

+    // Discards all channels by the leftmost one.
     ca->set_num_channels(1);
   }
 
@@ -722,6 +722,10 @@ int AudioProcessingImpl::ProcessStreamLocked() {
   RETURN_ON_ERR(public_submodules_->echo_control_mobile->ProcessCaptureAudio(
       ca, stream_delay_ms()));
 
+  if (capture_nonlocked_.beamformer_enabled) {
+    private_submodules_->beamformer->PostFilter(ca->split_data_f());
+  }
+
   public_submodules_->voice_detection->ProcessCaptureAudio(ca);
 
   if (constants_.use_experimental_agc &&