Reland "Reland "Add core multi-channel pipeline in AEC3 This CL adds basic the basic pipeline to support multi-channel processing in AEC3.""

This is a reland of a66395e72f9fc86873bf443579ec73c3d78af240

Original change's description:
> Reland "Add core multi-channel pipeline in AEC3 This CL adds basic the basic pipeline to support multi-channel processing in AEC3."
> 
> This is a reland of f3a197e55323aee974a932c52dd19fa88e5d4e38
> 
> Original change's description:
> > Add core multi-channel pipeline in AEC3
> > This CL adds basic the basic pipeline to support multi-channel
> > processing in AEC3.
> > 
> > Apart from that, it removes the 8 kHz processing support in several
> > places of the AEC3 code.
> > 
> > Bug: webrtc:10913
> > Change-Id: If5b75fa325ed0071deea94a7546cb4a7adf22137
> > Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/150332
> > Commit-Queue: Per Åhgren <peah@webrtc.org>
> > Reviewed-by: Sam Zackrisson <saza@webrtc.org>
> > Cr-Commit-Position: refs/heads/master@{#29017}
> 
> Bug: webrtc:10913
> Change-Id: Ifc4b13bd994cfd22dca8f8755fa5700617cc379d
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/151124
> Reviewed-by: Sam Zackrisson <saza@webrtc.org>
> Commit-Queue: Per Åhgren <peah@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#29034}

Bug: webrtc:10913
Change-Id: Id8da5666df8c86f290c73ad5dc9958199f1a7ebe
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/151127
Commit-Queue: Sam Zackrisson <saza@webrtc.org>
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29042}
diff --git a/modules/audio_processing/aec3/render_delay_buffer.cc b/modules/audio_processing/aec3/render_delay_buffer.cc
index 11fe450..379f5a1 100644
--- a/modules/audio_processing/aec3/render_delay_buffer.cc
+++ b/modules/audio_processing/aec3/render_delay_buffer.cc
@@ -39,12 +39,15 @@
 
 class RenderDelayBufferImpl final : public RenderDelayBuffer {
  public:
-  RenderDelayBufferImpl(const EchoCanceller3Config& config, int sample_rate_hz);
+  RenderDelayBufferImpl(const EchoCanceller3Config& config,
+                        int sample_rate_hz,
+                        size_t num_render_channels);
   RenderDelayBufferImpl() = delete;
   ~RenderDelayBufferImpl() override;
 
   void Reset() override;
-  BufferingEvent Insert(const std::vector<std::vector<float>>& block) override;
+  BufferingEvent Insert(
+      const std::vector<std::vector<std::vector<float>>>& block) override;
   BufferingEvent PrepareCaptureProcessing() override;
   bool AlignFromDelay(size_t delay) override;
   void AlignFromExternalDelay() override;
@@ -90,12 +93,11 @@
   bool external_audio_buffer_delay_verified_after_reset_ = false;
   size_t min_latency_blocks_ = 0;
   size_t excess_render_detection_counter_ = 0;
-  int sample_rate_hz_;
 
   int MapDelayToTotalDelay(size_t delay) const;
   int ComputeDelay() const;
   void ApplyTotalDelay(int delay);
-  void InsertBlock(const std::vector<std::vector<float>>& block,
+  void InsertBlock(const std::vector<std::vector<std::vector<float>>>& block,
                    int previous_write);
   bool DetectActiveRender(rtc::ArrayView<const float> x) const;
   bool DetectExcessRenderBlocks();
@@ -109,7 +111,8 @@
 int RenderDelayBufferImpl::instance_count_ = 0;
 
 RenderDelayBufferImpl::RenderDelayBufferImpl(const EchoCanceller3Config& config,
-                                             int sample_rate_hz)
+                                             int sample_rate_hz,
+                                             size_t num_render_channels)
     : data_dumper_(
           new ApmDataDumper(rtc::AtomicOps::Increment(&instance_count_))),
       optimization_(DetectOptimization()),
@@ -122,6 +125,7 @@
                                        config.delay.num_filters,
                                        config.filter.main.length_blocks),
               NumBandsForRate(sample_rate_hz),
+              num_render_channels,
               kBlockSize),
       spectra_(blocks_.buffer.size(), kFftLengthBy2Plus1),
       ffts_(blocks_.buffer.size()),
@@ -132,9 +136,7 @@
       render_decimator_(down_sampling_factor_),
       fft_(),
       render_ds_(sub_block_size_, 0.f),
-      buffer_headroom_(config.filter.main.length_blocks),
-      sample_rate_hz_(sample_rate_hz) {
-  RTC_DCHECK_GE(sample_rate_hz, 8000);
+      buffer_headroom_(config.filter.main.length_blocks) {
   RTC_DCHECK_EQ(blocks_.buffer.size(), ffts_.buffer.size());
   RTC_DCHECK_EQ(spectra_.buffer.size(), ffts_.buffer.size());
 
@@ -184,7 +186,7 @@
 
 // Inserts a new block into the render buffers.
 RenderDelayBuffer::BufferingEvent RenderDelayBufferImpl::Insert(
-    const std::vector<std::vector<float>>& block) {
+    const std::vector<std::vector<std::vector<float>>>& block) {
   ++render_call_counter_;
   if (delay_) {
     if (!last_call_was_render_) {
@@ -212,7 +214,7 @@
 
   // Detect and update render activity.
   if (!render_activity_) {
-    render_activity_counter_ += DetectActiveRender(block[0]) ? 1 : 0;
+    render_activity_counter_ += DetectActiveRender(block[0][0]) ? 1 : 0;
     render_activity_ = render_activity_counter_ >= 20;
   }
 
@@ -315,8 +317,7 @@
   }
 
   // Convert delay from milliseconds to blocks (rounded down).
-  external_audio_buffer_delay_ =
-      delay_ms >> ((sample_rate_hz_ == 8000) ? 1 : 2);
+  external_audio_buffer_delay_ = delay_ms >> 2;
 }
 
 bool RenderDelayBufferImpl::HasReceivedBufferDelay() {
@@ -359,7 +360,7 @@
 
 // Inserts a block into the render buffers.
 void RenderDelayBufferImpl::InsertBlock(
-    const std::vector<std::vector<float>>& block,
+    const std::vector<std::vector<std::vector<float>>>& block,
     int previous_write) {
   auto& b = blocks_;
   auto& lr = low_rate_;
@@ -372,13 +373,14 @@
     std::copy(block[k].begin(), block[k].end(), b.buffer[b.write][k].begin());
   }
 
-  data_dumper_->DumpWav("aec3_render_decimator_input", block[0].size(),
-                        block[0].data(), 16000, 1);
-  render_decimator_.Decimate(block[0], ds);
+  data_dumper_->DumpWav("aec3_render_decimator_input", block[0][0].size(),
+                        block[0][0].data(), 16000, 1);
+  render_decimator_.Decimate(block[0][0], ds);
   data_dumper_->DumpWav("aec3_render_decimator_output", ds.size(), ds.data(),
                         16000 / down_sampling_factor_, 1);
   std::copy(ds.rbegin(), ds.rend(), lr.buffer.begin() + lr.write);
-  fft_.PaddedFft(block[0], b.buffer[previous_write][0], &f.buffer[f.write]);
+  fft_.PaddedFft(block[0][0], b.buffer[previous_write][0][0],
+                 &f.buffer[f.write]);
   f.buffer[f.write].Spectrum(optimization_, s.buffer[s.write]);
 }
 
@@ -457,8 +459,9 @@
 }  // namespace
 
 RenderDelayBuffer* RenderDelayBuffer::Create(const EchoCanceller3Config& config,
-                                             int sample_rate_hz) {
-  return new RenderDelayBufferImpl(config, sample_rate_hz);
+                                             int sample_rate_hz,
+                                             size_t num_render_channels) {
+  return new RenderDelayBufferImpl(config, sample_rate_hz, num_render_channels);
 }
 
 }  // namespace webrtc