modules/audio_processing/aec3/render_delay_buffer.cc - src.git - Git at Google

 /*
  *  Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */

 #include "modules/audio_processing/aec3/render_delay_buffer.h"

 #include <string.h>
 #include <algorithm>
 #include <numeric>

 #include "modules/audio_processing/aec3/aec3_common.h"
 #include "modules/audio_processing/aec3/aec3_fft.h"
 #include "modules/audio_processing/aec3/block_processor.h"
 #include "modules/audio_processing/aec3/decimator.h"
 #include "modules/audio_processing/aec3/fft_buffer.h"
 #include "modules/audio_processing/aec3/fft_data.h"
 #include "modules/audio_processing/aec3/matrix_buffer.h"
 #include "rtc_base/atomicops.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/constructormagic.h"
 #include "rtc_base/logging.h"
 #include "system_wrappers/include/field_trial.h"

 namespace webrtc {
 namespace {

 bool EnableZeroExternalDelayHeadroom() {
   return !field_trial::IsEnabled(
       "WebRTC-Aec3ZeroExternalDelayHeadroomKillSwitch");
 }

 size_t GetDownSamplingFactor(const EchoCanceller3Config& config) {
   // Do not use down sampling factor 8 if kill switch is triggered.
   return (config.delay.down_sampling_factor == 8 &&
           field_trial::IsEnabled("WebRTC-Aec3DownSamplingFactor8KillSwitch"))
              ? 4
              : config.delay.down_sampling_factor;
 }

 class RenderDelayBufferImpl final : public RenderDelayBuffer {
  public:
   RenderDelayBufferImpl(const EchoCanceller3Config& config, size_t num_bands);
   ~RenderDelayBufferImpl() override;

   void Reset() override;
   BufferingEvent Insert(const std::vector<std::vector<float>>& block) override;
   BufferingEvent PrepareCaptureProcessing() override;
   bool SetDelay(size_t delay) override;
   size_t Delay() const override { return MapInternalDelayToExternalDelay(); }
   size_t MaxDelay() const override {
     return blocks_.buffer.size() - 1 - buffer_headroom_;
   }
   RenderBuffer* GetRenderBuffer() override { return &echo_remover_buffer_; }

   const DownsampledRenderBuffer& GetDownsampledRenderBuffer() const override {
     return low_rate_;
   }

   bool CausalDelay(size_t delay) const override;

   void SetAudioBufferDelay(size_t delay_ms) override;

  private:
   static int instance_count_;
   std::unique_ptr<ApmDataDumper> data_dumper_;
   const Aec3Optimization optimization_;
   const EchoCanceller3Config config_;
   size_t down_sampling_factor_;
   const bool use_zero_external_delay_headroom_;
   const int sub_block_size_;
   MatrixBuffer blocks_;
   VectorBuffer spectra_;
   FftBuffer ffts_;
   absl::optional<size_t> delay_;
   absl::optional<int> internal_delay_;
   RenderBuffer echo_remover_buffer_;
   DownsampledRenderBuffer low_rate_;
   Decimator render_decimator_;
   const std::vector<std::vector<float>> zero_block_;
   const Aec3Fft fft_;
   std::vector<float> render_ds_;
   const int buffer_headroom_;
   bool last_call_was_render_ = false;
   int num_api_calls_in_a_row_ = 0;
   int max_observed_jitter_ = 1;
   size_t capture_call_counter_ = 0;
   size_t render_call_counter_ = 0;
   bool render_activity_ = false;
   size_t render_activity_counter_ = 0;
   absl::optional<size_t> external_audio_buffer_delay_;
   bool external_delay_verified_after_reset_ = false;

   int LowRateBufferOffset() const { return DelayEstimatorOffset(config_) >> 1; }
   int MapExternalDelayToInternalDelay(size_t external_delay_blocks) const;
   int MapInternalDelayToExternalDelay() const;
   void ApplyDelay(int delay);
   void InsertBlock(const std::vector<std::vector<float>>& block,
                    int previous_write);
   bool DetectActiveRender(rtc::ArrayView<const float> x) const;

   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(RenderDelayBufferImpl);
 };

 // Increases the write indices for the render buffers.
 void IncreaseWriteIndices(int sub_block_size,
                           MatrixBuffer* blocks,
                           VectorBuffer* spectra,
                           FftBuffer* ffts,
                           DownsampledRenderBuffer* low_rate) {
   low_rate->UpdateWriteIndex(-sub_block_size);
   blocks->IncWriteIndex();
   spectra->DecWriteIndex();
   ffts->DecWriteIndex();
 }

 // Increases the read indices for the render buffers.
 void IncreaseReadIndices(const absl::optional<int>& delay,
                          int sub_block_size,
                          MatrixBuffer* blocks,
                          VectorBuffer* spectra,
                          FftBuffer* ffts,
                          DownsampledRenderBuffer* low_rate) {
   RTC_DCHECK_NE(low_rate->read, low_rate->write);
   low_rate->UpdateReadIndex(-sub_block_size);

   if (blocks->read != blocks->write) {
     blocks->IncReadIndex();
     spectra->DecReadIndex();
     ffts->DecReadIndex();
   } else {
     // Only allow underrun for blocks_ when the delay is not set.
     RTC_DCHECK(!delay);
   }
 }

 // Checks for a render buffer overrun.
 bool RenderOverrun(const MatrixBuffer& b, const DownsampledRenderBuffer& l) {
   return l.read == l.write || b.read == b.write;
 }

 // Checks for a render buffer underrun. If the delay is not specified, only the
 // low rate buffer underrun is counted as the delay offset for the other buffers
 // is unknown.
 bool RenderUnderrun(const absl::optional<int>& delay,
                     const MatrixBuffer& b,
                     const DownsampledRenderBuffer& l) {
   return l.read == l.write || (delay && b.read == b.write);
 }

 // Computes the latency in the buffer (the number of unread elements).
 int BufferLatency(const DownsampledRenderBuffer& l) {
   return (l.buffer.size() + l.read - l.write) % l.buffer.size();
 }

 // Computes the mismatch between the number of render and capture calls based on
 // the known offset (achieved during reset) of the low rate buffer.
 bool ApiCallSkew(const DownsampledRenderBuffer& low_rate_buffer,
                  int sub_block_size,
                  int low_rate_buffer_offset_sub_blocks) {
   int latency = BufferLatency(low_rate_buffer);
   int skew = abs(low_rate_buffer_offset_sub_blocks * sub_block_size - latency);
   int skew_limit = low_rate_buffer_offset_sub_blocks * sub_block_size;
   return skew >= skew_limit;
 }

 int RenderDelayBufferImpl::instance_count_ = 0;

 RenderDelayBufferImpl::RenderDelayBufferImpl(const EchoCanceller3Config& config,
                                              size_t num_bands)
     : data_dumper_(
           new ApmDataDumper(rtc::AtomicOps::Increment(&instance_count_))),
       optimization_(DetectOptimization()),
       config_(config),
       down_sampling_factor_(GetDownSamplingFactor(config)),
       use_zero_external_delay_headroom_(EnableZeroExternalDelayHeadroom()),
       sub_block_size_(static_cast<int>(down_sampling_factor_ > 0
                                            ? kBlockSize / down_sampling_factor_
                                            : kBlockSize)),
       blocks_(GetRenderDelayBufferSize(down_sampling_factor_,
                                        config.delay.num_filters,
                                        config.filter.main.length_blocks),
               num_bands,
               kBlockSize),
       spectra_(blocks_.buffer.size(), kFftLengthBy2Plus1),
       ffts_(blocks_.buffer.size()),
       delay_(config_.delay.default_delay),
       echo_remover_buffer_(&blocks_, &spectra_, &ffts_),
       low_rate_(GetDownSampledBufferSize(down_sampling_factor_,
                                          config.delay.num_filters)),
       render_decimator_(down_sampling_factor_),
       zero_block_(num_bands, std::vector<float>(kBlockSize, 0.f)),
       fft_(),
       render_ds_(sub_block_size_, 0.f),
       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());

   // Necessary condition to avoid unrecoverable echp due to noncausal alignment.
   RTC_DCHECK_EQ(DelayEstimatorOffset(config_), LowRateBufferOffset() * 2);
   Reset();
 }

 RenderDelayBufferImpl::~RenderDelayBufferImpl() = default;

 // Resets the buffer delays and clears the reported delays.
 void RenderDelayBufferImpl::Reset() {
   last_call_was_render_ = false;
   num_api_calls_in_a_row_ = 1;

   // Pre-fill the low rate buffer (which is used for delay estimation) to add
   // headroom for the allowed api call jitter.
   low_rate_.read = low_rate_.OffsetIndex(
       low_rate_.write, LowRateBufferOffset() * sub_block_size_);

   // Check for any external audio buffer delay and whether it is feasible.
   if (external_audio_buffer_delay_) {
     const size_t headroom = use_zero_external_delay_headroom_ ? 0 : 2;
     size_t external_delay_to_set = 0;
     if (*external_audio_buffer_delay_ < headroom) {
       external_delay_to_set = 0;
     } else {
       external_delay_to_set = *external_audio_buffer_delay_ - headroom;
     }

     external_delay_to_set = std::min(external_delay_to_set, MaxDelay());

     // When an external delay estimate is available, use that delay as the
     // initial render buffer delay.
     internal_delay_ = external_delay_to_set;
     ApplyDelay(*internal_delay_);
     delay_ = MapInternalDelayToExternalDelay();

     external_delay_verified_after_reset_ = false;
   } else {
     // If an external delay estimate is not available, use that delay as the
     // initial delay. Set the render buffer delays to the default delay.
     ApplyDelay(config_.delay.default_delay);

     // Unset the delays which are set by SetDelay.
     delay_ = absl::nullopt;
     internal_delay_ = absl::nullopt;
   }
 }

 // Inserts a new block into the render buffers.
 RenderDelayBuffer::BufferingEvent RenderDelayBufferImpl::Insert(
     const std::vector<std::vector<float>>& block) {
   ++render_call_counter_;
   if (delay_) {
     if (!last_call_was_render_) {
       last_call_was_render_ = true;
       num_api_calls_in_a_row_ = 1;
     } else {
       if (++num_api_calls_in_a_row_ > max_observed_jitter_) {
         max_observed_jitter_ = num_api_calls_in_a_row_;
         RTC_LOG(LS_WARNING)
             << "New max number api jitter observed at render block "
             << render_call_counter_ << ":  " << num_api_calls_in_a_row_
             << " blocks";
       }
     }
   }

   // Increase the write indices to where the new blocks should be written.
   const int previous_write = blocks_.write;
   IncreaseWriteIndices(sub_block_size_, &blocks_, &spectra_, &ffts_,
                        &low_rate_);

   // Allow overrun and do a reset when render overrun occurrs due to more render
   // data being inserted than capture data is received.
   BufferingEvent event = RenderOverrun(blocks_, low_rate_)
                              ? BufferingEvent::kRenderOverrun
                              : BufferingEvent::kNone;

   // Detect and update render activity.
   if (!render_activity_) {
     render_activity_counter_ += DetectActiveRender(block[0]) ? 1 : 0;
     render_activity_ = render_activity_counter_ >= 20;
   }

   // Insert the new render block into the specified position.
   InsertBlock(block, previous_write);

   if (event != BufferingEvent::kNone) {
     Reset();
   }

   return event;
 }

 // Prepares the render buffers for processing another capture block.
 RenderDelayBuffer::BufferingEvent
 RenderDelayBufferImpl::PrepareCaptureProcessing() {
   BufferingEvent event = BufferingEvent::kNone;
   ++capture_call_counter_;

   if (delay_) {
     if (last_call_was_render_) {
       last_call_was_render_ = false;
       num_api_calls_in_a_row_ = 1;
     } else {
       if (++num_api_calls_in_a_row_ > max_observed_jitter_) {
         max_observed_jitter_ = num_api_calls_in_a_row_;
         RTC_LOG(LS_WARNING)
             << "New max number api jitter observed at capture block "
             << capture_call_counter_ << ":  " << num_api_calls_in_a_row_
             << " blocks";
       }
     }
   }

   if (RenderUnderrun(internal_delay_, blocks_, low_rate_)) {
     // Don't increase the read indices if there is a render underrun.
     event = BufferingEvent::kRenderUnderrun;
   } else {
     // Increase the read indices in the render buffers to point to the most
     // recent block to use in the capture processing.
     IncreaseReadIndices(internal_delay_, sub_block_size_, &blocks_, &spectra_,
                         &ffts_, &low_rate_);

     // Check for skew in the API calls which, if too large, causes the delay
     // estimation to be noncausal. Doing this check after the render indice
     // increase saves one unit of allowed skew. Note that the skew check only
     // should need to be one-sided as one of the skew directions results in an
     // underrun.
     bool skew = ApiCallSkew(low_rate_, sub_block_size_, LowRateBufferOffset());
     event = skew ? BufferingEvent::kApiCallSkew : BufferingEvent::kNone;
   }

   if (event != BufferingEvent::kNone) {
     Reset();
   }

   echo_remover_buffer_.SetRenderActivity(render_activity_);
   if (render_activity_) {
     render_activity_counter_ = 0;
     render_activity_ = false;
   }

   return event;
 }

 // Sets the delay and returns a bool indicating whether the delay was changed.
 bool RenderDelayBufferImpl::SetDelay(size_t delay) {
   if (!external_delay_verified_after_reset_ && external_audio_buffer_delay_ &&
       delay_) {
     int difference = static_cast<int>(delay) - static_cast<int>(*delay_);
     RTC_LOG(LS_WARNING) << "Mismatch between first estimated delay after reset "
                            "and external delay: "
                         << difference << " blocks";
     external_delay_verified_after_reset_ = true;
   }
   if (delay_ && *delay_ == delay) {
     return false;
   }
   delay_ = delay;

   // Compute the internal delay and limit the delay to the allowed range.
   int internal_delay = MapExternalDelayToInternalDelay(*delay_);
   internal_delay_ =
       std::min(MaxDelay(), static_cast<size_t>(std::max(internal_delay, 0)));

   // Apply the delay to the buffers.
   ApplyDelay(*internal_delay_);
   return true;
 }

 // Returns whether the specified delay is causal.
 bool RenderDelayBufferImpl::CausalDelay(size_t delay) const {
   // Compute the internal delay and limit the delay to the allowed range.
   int internal_delay = MapExternalDelayToInternalDelay(delay);
   internal_delay =
       std::min(MaxDelay(), static_cast<size_t>(std::max(internal_delay, 0)));

   return internal_delay >=
          static_cast<int>(config_.delay.min_echo_path_delay_blocks);
 }

 void RenderDelayBufferImpl::SetAudioBufferDelay(size_t delay_ms) {
   if (!external_audio_buffer_delay_) {
     RTC_LOG(LS_WARNING)
         << "Receiving a first reported externally buffer delay of " << delay_ms
         << " ms.";
   }

   // Convert delay from milliseconds to blocks (rounded down).
   external_audio_buffer_delay_ = delay_ms / 4;
 }

 // Maps the externally computed delay to the delay used internally.
 int RenderDelayBufferImpl::MapExternalDelayToInternalDelay(
     size_t external_delay_blocks) const {
   const int latency = BufferLatency(low_rate_);
   RTC_DCHECK_LT(0, sub_block_size_);
   RTC_DCHECK_EQ(0, latency % sub_block_size_);
   int latency_blocks = latency / sub_block_size_;
   return latency_blocks + static_cast<int>(external_delay_blocks) -
          DelayEstimatorOffset(config_);
 }

 // Maps the internally used delay to the delay used externally.
 int RenderDelayBufferImpl::MapInternalDelayToExternalDelay() const {
   const int latency = BufferLatency(low_rate_);
   int latency_blocks = latency / sub_block_size_;
   int internal_delay = spectra_.read >= spectra_.write
                            ? spectra_.read - spectra_.write
                            : spectra_.size + spectra_.read - spectra_.write;

   return internal_delay - latency_blocks + DelayEstimatorOffset(config_);
 }

 // Set the read indices according to the delay.
 void RenderDelayBufferImpl::ApplyDelay(int delay) {
   RTC_LOG(LS_WARNING) << "Applying internal delay of " << delay << " blocks.";
   blocks_.read = blocks_.OffsetIndex(blocks_.write, -delay);
   spectra_.read = spectra_.OffsetIndex(spectra_.write, delay);
   ffts_.read = ffts_.OffsetIndex(ffts_.write, delay);
 }

 // Inserts a block into the render buffers.
 void RenderDelayBufferImpl::InsertBlock(
     const std::vector<std::vector<float>>& block,
     int previous_write) {
   auto& b = blocks_;
   auto& lr = low_rate_;
   auto& ds = render_ds_;
   auto& f = ffts_;
   auto& s = spectra_;
   RTC_DCHECK_EQ(block.size(), b.buffer[b.write].size());
   for (size_t k = 0; k < block.size(); ++k) {
     RTC_DCHECK_EQ(block[k].size(), b.buffer[b.write][k].size());
     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_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]);
   f.buffer[f.write].Spectrum(optimization_, s.buffer[s.write]);
 }

 bool RenderDelayBufferImpl::DetectActiveRender(
     rtc::ArrayView<const float> x) const {
   const float x_energy = std::inner_product(x.begin(), x.end(), x.begin(), 0.f);
   return x_energy > (config_.render_levels.active_render_limit *
                      config_.render_levels.active_render_limit) *
                         kFftLengthBy2;
 }

 }  // namespace

 int RenderDelayBuffer::RenderDelayBuffer::DelayEstimatorOffset(
     const EchoCanceller3Config& config) {
   return config.delay.api_call_jitter_blocks * 2;
 }

 RenderDelayBuffer* RenderDelayBuffer::Create(const EchoCanceller3Config& config,
                                              size_t num_bands) {
   return new RenderDelayBufferImpl(config, num_bands);
 }

 }  // namespace webrtc
	/*
	* Copyright (c) 2017 The WebRTC project authors. All Rights Reserved.
	*
	* Use of this source code is governed by a BSD-style license
	* that can be found in the LICENSE file in the root of the source
	* tree. An additional intellectual property rights grant can be found
	* in the file PATENTS. All contributing project authors may
	* be found in the AUTHORS file in the root of the source tree.
	*/

	#include "modules/audio_processing/aec3/render_delay_buffer.h"

	#include <string.h>
	#include <algorithm>
	#include <numeric>

	#include "modules/audio_processing/aec3/aec3_common.h"
	#include "modules/audio_processing/aec3/aec3_fft.h"
	#include "modules/audio_processing/aec3/block_processor.h"
	#include "modules/audio_processing/aec3/decimator.h"
	#include "modules/audio_processing/aec3/fft_buffer.h"
	#include "modules/audio_processing/aec3/fft_data.h"
	#include "modules/audio_processing/aec3/matrix_buffer.h"
	#include "rtc_base/atomicops.h"
	#include "rtc_base/checks.h"
	#include "rtc_base/constructormagic.h"
	#include "rtc_base/logging.h"
	#include "system_wrappers/include/field_trial.h"

	namespace webrtc {
	namespace {

	bool EnableZeroExternalDelayHeadroom() {
	return !field_trial::IsEnabled(
	"WebRTC-Aec3ZeroExternalDelayHeadroomKillSwitch");
	}

	size_t GetDownSamplingFactor(const EchoCanceller3Config& config) {
	// Do not use down sampling factor 8 if kill switch is triggered.
	return (config.delay.down_sampling_factor == 8 &&
	field_trial::IsEnabled("WebRTC-Aec3DownSamplingFactor8KillSwitch"))
	? 4
	: config.delay.down_sampling_factor;
	}

	class RenderDelayBufferImpl final : public RenderDelayBuffer {
	public:
	RenderDelayBufferImpl(const EchoCanceller3Config& config, size_t num_bands);
	~RenderDelayBufferImpl() override;

	void Reset() override;
	BufferingEvent Insert(const std::vector<std::vector<float>>& block) override;
	BufferingEvent PrepareCaptureProcessing() override;
	bool SetDelay(size_t delay) override;
	size_t Delay() const override { return MapInternalDelayToExternalDelay(); }
	size_t MaxDelay() const override {
	return blocks_.buffer.size() - 1 - buffer_headroom_;
	}
	RenderBuffer* GetRenderBuffer() override { return &echo_remover_buffer_; }

	const DownsampledRenderBuffer& GetDownsampledRenderBuffer() const override {
	return low_rate_;
	}

	bool CausalDelay(size_t delay) const override;

	void SetAudioBufferDelay(size_t delay_ms) override;

	private:
	static int instance_count_;
	std::unique_ptr<ApmDataDumper> data_dumper_;
	const Aec3Optimization optimization_;
	const EchoCanceller3Config config_;
	size_t down_sampling_factor_;
	const bool use_zero_external_delay_headroom_;
	const int sub_block_size_;
	MatrixBuffer blocks_;
	VectorBuffer spectra_;
	FftBuffer ffts_;
	absl::optional<size_t> delay_;
	absl::optional<int> internal_delay_;
	RenderBuffer echo_remover_buffer_;
	DownsampledRenderBuffer low_rate_;
	Decimator render_decimator_;
	const std::vector<std::vector<float>> zero_block_;
	const Aec3Fft fft_;
	std::vector<float> render_ds_;
	const int buffer_headroom_;
	bool last_call_was_render_ = false;
	int num_api_calls_in_a_row_ = 0;
	int max_observed_jitter_ = 1;
	size_t capture_call_counter_ = 0;
	size_t render_call_counter_ = 0;
	bool render_activity_ = false;
	size_t render_activity_counter_ = 0;
	absl::optional<size_t> external_audio_buffer_delay_;
	bool external_delay_verified_after_reset_ = false;

	int LowRateBufferOffset() const { return DelayEstimatorOffset(config_) >> 1; }
	int MapExternalDelayToInternalDelay(size_t external_delay_blocks) const;
	int MapInternalDelayToExternalDelay() const;
	void ApplyDelay(int delay);
	void InsertBlock(const std::vector<std::vector<float>>& block,
	int previous_write);
	bool DetectActiveRender(rtc::ArrayView<const float> x) const;

	RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(RenderDelayBufferImpl);
	};

	// Increases the write indices for the render buffers.
	void IncreaseWriteIndices(int sub_block_size,
	MatrixBuffer* blocks,
	VectorBuffer* spectra,
	FftBuffer* ffts,
	DownsampledRenderBuffer* low_rate) {
	low_rate->UpdateWriteIndex(-sub_block_size);
	blocks->IncWriteIndex();
	spectra->DecWriteIndex();
	ffts->DecWriteIndex();
	}

	// Increases the read indices for the render buffers.
	void IncreaseReadIndices(const absl::optional<int>& delay,
	int sub_block_size,
	MatrixBuffer* blocks,
	VectorBuffer* spectra,
	FftBuffer* ffts,
	DownsampledRenderBuffer* low_rate) {
	RTC_DCHECK_NE(low_rate->read, low_rate->write);
	low_rate->UpdateReadIndex(-sub_block_size);

	if (blocks->read != blocks->write) {
	blocks->IncReadIndex();
	spectra->DecReadIndex();
	ffts->DecReadIndex();
	} else {
	// Only allow underrun for blocks_ when the delay is not set.
	RTC_DCHECK(!delay);
	}
	}

	// Checks for a render buffer overrun.
	bool RenderOverrun(const MatrixBuffer& b, const DownsampledRenderBuffer& l) {
	return l.read == l.write \|\| b.read == b.write;
	}

	// Checks for a render buffer underrun. If the delay is not specified, only the
	// low rate buffer underrun is counted as the delay offset for the other buffers
	// is unknown.
	bool RenderUnderrun(const absl::optional<int>& delay,
	const MatrixBuffer& b,
	const DownsampledRenderBuffer& l) {
	return l.read == l.write \|\| (delay && b.read == b.write);
	}

	// Computes the latency in the buffer (the number of unread elements).
	int BufferLatency(const DownsampledRenderBuffer& l) {
	return (l.buffer.size() + l.read - l.write) % l.buffer.size();
	}

	// Computes the mismatch between the number of render and capture calls based on
	// the known offset (achieved during reset) of the low rate buffer.
	bool ApiCallSkew(const DownsampledRenderBuffer& low_rate_buffer,
	int sub_block_size,
	int low_rate_buffer_offset_sub_blocks) {
	int latency = BufferLatency(low_rate_buffer);
	int skew = abs(low_rate_buffer_offset_sub_blocks * sub_block_size - latency);
	int skew_limit = low_rate_buffer_offset_sub_blocks * sub_block_size;
	return skew >= skew_limit;
	}

	int RenderDelayBufferImpl::instance_count_ = 0;

	RenderDelayBufferImpl::RenderDelayBufferImpl(const EchoCanceller3Config& config,
	size_t num_bands)
	: data_dumper_(
	new ApmDataDumper(rtc::AtomicOps::Increment(&instance_count_))),
	optimization_(DetectOptimization()),
	config_(config),
	down_sampling_factor_(GetDownSamplingFactor(config)),
	use_zero_external_delay_headroom_(EnableZeroExternalDelayHeadroom()),
	sub_block_size_(static_cast<int>(down_sampling_factor_ > 0
	? kBlockSize / down_sampling_factor_
	: kBlockSize)),
	blocks_(GetRenderDelayBufferSize(down_sampling_factor_,
	config.delay.num_filters,
	config.filter.main.length_blocks),
	num_bands,
	kBlockSize),
	spectra_(blocks_.buffer.size(), kFftLengthBy2Plus1),
	ffts_(blocks_.buffer.size()),
	delay_(config_.delay.default_delay),
	echo_remover_buffer_(&blocks_, &spectra_, &ffts_),
	low_rate_(GetDownSampledBufferSize(down_sampling_factor_,
	config.delay.num_filters)),
	render_decimator_(down_sampling_factor_),
	zero_block_(num_bands, std::vector<float>(kBlockSize, 0.f)),
	fft_(),
	render_ds_(sub_block_size_, 0.f),
	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());

	// Necessary condition to avoid unrecoverable echp due to noncausal alignment.
	RTC_DCHECK_EQ(DelayEstimatorOffset(config_), LowRateBufferOffset() * 2);
	Reset();
	}

	RenderDelayBufferImpl::~RenderDelayBufferImpl() = default;

	// Resets the buffer delays and clears the reported delays.
	void RenderDelayBufferImpl::Reset() {
	last_call_was_render_ = false;
	num_api_calls_in_a_row_ = 1;

	// Pre-fill the low rate buffer (which is used for delay estimation) to add
	// headroom for the allowed api call jitter.
	low_rate_.read = low_rate_.OffsetIndex(
	low_rate_.write, LowRateBufferOffset() * sub_block_size_);

	// Check for any external audio buffer delay and whether it is feasible.
	if (external_audio_buffer_delay_) {
	const size_t headroom = use_zero_external_delay_headroom_ ? 0 : 2;
	size_t external_delay_to_set = 0;
	if (*external_audio_buffer_delay_ < headroom) {
	external_delay_to_set = 0;
	} else {
	external_delay_to_set = *external_audio_buffer_delay_ - headroom;
	}

	external_delay_to_set = std::min(external_delay_to_set, MaxDelay());

	// When an external delay estimate is available, use that delay as the
	// initial render buffer delay.
	internal_delay_ = external_delay_to_set;
	ApplyDelay(*internal_delay_);
	delay_ = MapInternalDelayToExternalDelay();

	external_delay_verified_after_reset_ = false;
	} else {
	// If an external delay estimate is not available, use that delay as the
	// initial delay. Set the render buffer delays to the default delay.
	ApplyDelay(config_.delay.default_delay);

	// Unset the delays which are set by SetDelay.
	delay_ = absl::nullopt;
	internal_delay_ = absl::nullopt;
	}
	}

	// Inserts a new block into the render buffers.
	RenderDelayBuffer::BufferingEvent RenderDelayBufferImpl::Insert(
	const std::vector<std::vector<float>>& block) {
	++render_call_counter_;
	if (delay_) {
	if (!last_call_was_render_) {
	last_call_was_render_ = true;
	num_api_calls_in_a_row_ = 1;
	} else {
	if (++num_api_calls_in_a_row_ > max_observed_jitter_) {
	max_observed_jitter_ = num_api_calls_in_a_row_;
	RTC_LOG(LS_WARNING)
	<< "New max number api jitter observed at render block "
	<< render_call_counter_ << ": " << num_api_calls_in_a_row_
	<< " blocks";
	}
	}
	}

	// Increase the write indices to where the new blocks should be written.
	const int previous_write = blocks_.write;
	IncreaseWriteIndices(sub_block_size_, &blocks_, &spectra_, &ffts_,
	&low_rate_);

	// Allow overrun and do a reset when render overrun occurrs due to more render
	// data being inserted than capture data is received.
	BufferingEvent event = RenderOverrun(blocks_, low_rate_)
	? BufferingEvent::kRenderOverrun
	: BufferingEvent::kNone;

	// Detect and update render activity.
	if (!render_activity_) {
	render_activity_counter_ += DetectActiveRender(block[0]) ? 1 : 0;
	render_activity_ = render_activity_counter_ >= 20;
	}

	// Insert the new render block into the specified position.
	InsertBlock(block, previous_write);

	if (event != BufferingEvent::kNone) {
	Reset();
	}

	return event;
	}

	// Prepares the render buffers for processing another capture block.
	RenderDelayBuffer::BufferingEvent
	RenderDelayBufferImpl::PrepareCaptureProcessing() {
	BufferingEvent event = BufferingEvent::kNone;
	++capture_call_counter_;

	if (delay_) {
	if (last_call_was_render_) {
	last_call_was_render_ = false;
	num_api_calls_in_a_row_ = 1;
	} else {
	if (++num_api_calls_in_a_row_ > max_observed_jitter_) {
	max_observed_jitter_ = num_api_calls_in_a_row_;
	RTC_LOG(LS_WARNING)
	<< "New max number api jitter observed at capture block "
	<< capture_call_counter_ << ": " << num_api_calls_in_a_row_
	<< " blocks";
	}
	}
	}

	if (RenderUnderrun(internal_delay_, blocks_, low_rate_)) {
	// Don't increase the read indices if there is a render underrun.
	event = BufferingEvent::kRenderUnderrun;
	} else {
	// Increase the read indices in the render buffers to point to the most
	// recent block to use in the capture processing.
	IncreaseReadIndices(internal_delay_, sub_block_size_, &blocks_, &spectra_,
	&ffts_, &low_rate_);

	// Check for skew in the API calls which, if too large, causes the delay
	// estimation to be noncausal. Doing this check after the render indice
	// increase saves one unit of allowed skew. Note that the skew check only
	// should need to be one-sided as one of the skew directions results in an
	// underrun.
	bool skew = ApiCallSkew(low_rate_, sub_block_size_, LowRateBufferOffset());
	event = skew ? BufferingEvent::kApiCallSkew : BufferingEvent::kNone;
	}

	if (event != BufferingEvent::kNone) {
	Reset();
	}

	echo_remover_buffer_.SetRenderActivity(render_activity_);
	if (render_activity_) {
	render_activity_counter_ = 0;
	render_activity_ = false;
	}

	return event;
	}

	// Sets the delay and returns a bool indicating whether the delay was changed.
	bool RenderDelayBufferImpl::SetDelay(size_t delay) {
	if (!external_delay_verified_after_reset_ && external_audio_buffer_delay_ &&
	delay_) {
	int difference = static_cast<int>(delay) - static_cast<int>(*delay_);
	RTC_LOG(LS_WARNING) << "Mismatch between first estimated delay after reset "
	"and external delay: "
	<< difference << " blocks";
	external_delay_verified_after_reset_ = true;
	}
	if (delay_ && *delay_ == delay) {
	return false;
	}
	delay_ = delay;

	// Compute the internal delay and limit the delay to the allowed range.
	int internal_delay = MapExternalDelayToInternalDelay(*delay_);
	internal_delay_ =
	std::min(MaxDelay(), static_cast<size_t>(std::max(internal_delay, 0)));

	// Apply the delay to the buffers.
	ApplyDelay(*internal_delay_);
	return true;
	}

	// Returns whether the specified delay is causal.
	bool RenderDelayBufferImpl::CausalDelay(size_t delay) const {
	// Compute the internal delay and limit the delay to the allowed range.
	int internal_delay = MapExternalDelayToInternalDelay(delay);
	internal_delay =
	std::min(MaxDelay(), static_cast<size_t>(std::max(internal_delay, 0)));

	return internal_delay >=
	static_cast<int>(config_.delay.min_echo_path_delay_blocks);
	}

	void RenderDelayBufferImpl::SetAudioBufferDelay(size_t delay_ms) {
	if (!external_audio_buffer_delay_) {
	RTC_LOG(LS_WARNING)
	<< "Receiving a first reported externally buffer delay of " << delay_ms
	<< " ms.";
	}

	// Convert delay from milliseconds to blocks (rounded down).
	external_audio_buffer_delay_ = delay_ms / 4;
	}

	// Maps the externally computed delay to the delay used internally.
	int RenderDelayBufferImpl::MapExternalDelayToInternalDelay(
	size_t external_delay_blocks) const {
	const int latency = BufferLatency(low_rate_);
	RTC_DCHECK_LT(0, sub_block_size_);
	RTC_DCHECK_EQ(0, latency % sub_block_size_);
	int latency_blocks = latency / sub_block_size_;
	return latency_blocks + static_cast<int>(external_delay_blocks) -
	DelayEstimatorOffset(config_);
	}

	// Maps the internally used delay to the delay used externally.
	int RenderDelayBufferImpl::MapInternalDelayToExternalDelay() const {
	const int latency = BufferLatency(low_rate_);
	int latency_blocks = latency / sub_block_size_;
	int internal_delay = spectra_.read >= spectra_.write
	? spectra_.read - spectra_.write
	: spectra_.size + spectra_.read - spectra_.write;

	return internal_delay - latency_blocks + DelayEstimatorOffset(config_);
	}

	// Set the read indices according to the delay.
	void RenderDelayBufferImpl::ApplyDelay(int delay) {
	RTC_LOG(LS_WARNING) << "Applying internal delay of " << delay << " blocks.";
	blocks_.read = blocks_.OffsetIndex(blocks_.write, -delay);
	spectra_.read = spectra_.OffsetIndex(spectra_.write, delay);
	ffts_.read = ffts_.OffsetIndex(ffts_.write, delay);
	}

	// Inserts a block into the render buffers.
	void RenderDelayBufferImpl::InsertBlock(
	const std::vector<std::vector<float>>& block,
	int previous_write) {
	auto& b = blocks_;
	auto& lr = low_rate_;
	auto& ds = render_ds_;
	auto& f = ffts_;
	auto& s = spectra_;
	RTC_DCHECK_EQ(block.size(), b.buffer[b.write].size());
	for (size_t k = 0; k < block.size(); ++k) {
	RTC_DCHECK_EQ(block[k].size(), b.buffer[b.write][k].size());
	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_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]);
	f.buffer[f.write].Spectrum(optimization_, s.buffer[s.write]);
	}

	bool RenderDelayBufferImpl::DetectActiveRender(
	rtc::ArrayView<const float> x) const {
	const float x_energy = std::inner_product(x.begin(), x.end(), x.begin(), 0.f);
	return x_energy > (config_.render_levels.active_render_limit *
	config_.render_levels.active_render_limit) *
	kFftLengthBy2;
	}

	} // namespace

	int RenderDelayBuffer::RenderDelayBuffer::DelayEstimatorOffset(
	const EchoCanceller3Config& config) {
	return config.delay.api_call_jitter_blocks * 2;
	}

	RenderDelayBuffer* RenderDelayBuffer::Create(const EchoCanceller3Config& config,
	size_t num_bands) {
	return new RenderDelayBufferImpl(config, num_bands);
	}

	} // namespace webrtc