modules/audio_processing/agc/agc_manager_direct.cc - src - Git at Google

 /*
  *  Copyright (c) 2013 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/agc/agc_manager_direct.h"

 #include <cmath>

 #ifdef WEBRTC_AGC_DEBUG_DUMP
 #include <cstdio>
 #endif

 #include "modules/audio_processing/agc/gain_map_internal.h"
 #include "modules/audio_processing/gain_control_impl.h"
 #include "modules/include/module_common_types.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/numerics/safe_minmax.h"
 #include "system_wrappers/include/metrics.h"

 namespace webrtc {

 namespace {

 // Amount the microphone level is lowered with every clipping event.
 const int kClippedLevelStep = 15;
 // Proportion of clipped samples required to declare a clipping event.
 const float kClippedRatioThreshold = 0.1f;
 // Time in frames to wait after a clipping event before checking again.
 const int kClippedWaitFrames = 300;

 // Amount of error we tolerate in the microphone level (presumably due to OS
 // quantization) before we assume the user has manually adjusted the microphone.
 const int kLevelQuantizationSlack = 25;

 const int kDefaultCompressionGain = 7;
 const int kMaxCompressionGain = 12;
 const int kMinCompressionGain = 2;
 // Controls the rate of compression changes towards the target.
 const float kCompressionGainStep = 0.05f;

 const int kMaxMicLevel = 255;
 static_assert(kGainMapSize > kMaxMicLevel, "gain map too small");
 const int kMinMicLevel = 12;

 // Prevent very large microphone level changes.
 const int kMaxResidualGainChange = 15;

 // Maximum additional gain allowed to compensate for microphone level
 // restrictions from clipping events.
 const int kSurplusCompressionGain = 6;

 int ClampLevel(int mic_level) {
   return rtc::SafeClamp(mic_level, kMinMicLevel, kMaxMicLevel);
 }

 int LevelFromGainError(int gain_error, int level) {
   RTC_DCHECK_GE(level, 0);
   RTC_DCHECK_LE(level, kMaxMicLevel);
   if (gain_error == 0) {
     return level;
   }
   // TODO(ajm): Could be made more efficient with a binary search.
   int new_level = level;
   if (gain_error > 0) {
     while (kGainMap[new_level] - kGainMap[level] < gain_error &&
           new_level < kMaxMicLevel) {
       ++new_level;
     }
   } else {
     while (kGainMap[new_level] - kGainMap[level] > gain_error &&
           new_level > kMinMicLevel) {
       --new_level;
     }
   }
   return new_level;
 }

 }  // namespace

 // Facility for dumping debug audio files. All methods are no-ops in the
 // default case where WEBRTC_AGC_DEBUG_DUMP is undefined.
 class DebugFile {
 #ifdef WEBRTC_AGC_DEBUG_DUMP
  public:
   explicit DebugFile(const char* filename)
       : file_(fopen(filename, "wb")) {
     RTC_DCHECK(file_);
   }
   ~DebugFile() {
     fclose(file_);
   }
   void Write(const int16_t* data, size_t length_samples) {
     fwrite(data, 1, length_samples * sizeof(int16_t), file_);
   }
  private:
   FILE* file_;
 #else
  public:
   explicit DebugFile(const char* filename) {
   }
   ~DebugFile() {
   }
   void Write(const int16_t* data, size_t length_samples) {
   }
 #endif  // WEBRTC_AGC_DEBUG_DUMP
 };

 AgcManagerDirect::AgcManagerDirect(GainControl* gctrl,
                                    VolumeCallbacks* volume_callbacks,
                                    int startup_min_level,
                                    int clipped_level_min)
     : agc_(new Agc()),
       gctrl_(gctrl),
       volume_callbacks_(volume_callbacks),
       frames_since_clipped_(kClippedWaitFrames),
       level_(0),
       max_level_(kMaxMicLevel),
       max_compression_gain_(kMaxCompressionGain),
       target_compression_(kDefaultCompressionGain),
       compression_(target_compression_),
       compression_accumulator_(compression_),
       capture_muted_(false),
       check_volume_on_next_process_(true),  // Check at startup.
       startup_(true),
       startup_min_level_(ClampLevel(startup_min_level)),
       clipped_level_min_(clipped_level_min),
       file_preproc_(new DebugFile("agc_preproc.pcm")),
       file_postproc_(new DebugFile("agc_postproc.pcm")) {}

 AgcManagerDirect::AgcManagerDirect(Agc* agc,
                                    GainControl* gctrl,
                                    VolumeCallbacks* volume_callbacks,
                                    int startup_min_level,
                                    int clipped_level_min)
     : agc_(agc),
       gctrl_(gctrl),
       volume_callbacks_(volume_callbacks),
       frames_since_clipped_(kClippedWaitFrames),
       level_(0),
       max_level_(kMaxMicLevel),
       max_compression_gain_(kMaxCompressionGain),
       target_compression_(kDefaultCompressionGain),
       compression_(target_compression_),
       compression_accumulator_(compression_),
       capture_muted_(false),
       check_volume_on_next_process_(true),  // Check at startup.
       startup_(true),
       startup_min_level_(ClampLevel(startup_min_level)),
       clipped_level_min_(clipped_level_min),
       file_preproc_(new DebugFile("agc_preproc.pcm")),
       file_postproc_(new DebugFile("agc_postproc.pcm")) {}

 AgcManagerDirect::~AgcManagerDirect() {}

 int AgcManagerDirect::Initialize() {
   max_level_ = kMaxMicLevel;
   max_compression_gain_ = kMaxCompressionGain;
   target_compression_ = kDefaultCompressionGain;
   compression_ = target_compression_;
   compression_accumulator_ = compression_;
   capture_muted_ = false;
   check_volume_on_next_process_ = true;
   // TODO(bjornv): Investigate if we need to reset |startup_| as well. For
   // example, what happens when we change devices.

   if (gctrl_->set_mode(GainControl::kFixedDigital) != 0) {
     RTC_LOG(LS_ERROR) << "set_mode(GainControl::kFixedDigital) failed.";
     return -1;
   }
   if (gctrl_->set_target_level_dbfs(2) != 0) {
     RTC_LOG(LS_ERROR) << "set_target_level_dbfs(2) failed.";
     return -1;
   }
   if (gctrl_->set_compression_gain_db(kDefaultCompressionGain) != 0) {
     RTC_LOG(LS_ERROR)
         << "set_compression_gain_db(kDefaultCompressionGain) failed.";
     return -1;
   }
   if (gctrl_->enable_limiter(true) != 0) {
     RTC_LOG(LS_ERROR) << "enable_limiter(true) failed.";
     return -1;
   }
   return 0;
 }

 void AgcManagerDirect::AnalyzePreProcess(int16_t* audio,
                                          int num_channels,
                                          size_t samples_per_channel) {
   size_t length = num_channels * samples_per_channel;
   if (capture_muted_) {
     return;
   }

   file_preproc_->Write(audio, length);

   if (frames_since_clipped_ < kClippedWaitFrames) {
     ++frames_since_clipped_;
     return;
   }

   // Check for clipped samples, as the AGC has difficulty detecting pitch
   // under clipping distortion. We do this in the preprocessing phase in order
   // to catch clipped echo as well.
   //
   // If we find a sufficiently clipped frame, drop the current microphone level
   // and enforce a new maximum level, dropped the same amount from the current
   // maximum. This harsh treatment is an effort to avoid repeated clipped echo
   // events. As compensation for this restriction, the maximum compression
   // gain is increased, through SetMaxLevel().
   float clipped_ratio = agc_->AnalyzePreproc(audio, length);
   if (clipped_ratio > kClippedRatioThreshold) {
     RTC_DLOG(LS_INFO) << "[agc] Clipping detected. clipped_ratio="
                       << clipped_ratio;
     // Always decrease the maximum level, even if the current level is below
     // threshold.
     SetMaxLevel(std::max(clipped_level_min_, max_level_ - kClippedLevelStep));
     RTC_HISTOGRAM_BOOLEAN("WebRTC.Audio.AgcClippingAdjustmentAllowed",
                           level_ - kClippedLevelStep >= clipped_level_min_);
     if (level_ > clipped_level_min_) {
       // Don't try to adjust the level if we're already below the limit. As
       // a consequence, if the user has brought the level above the limit, we
       // will still not react until the postproc updates the level.
       SetLevel(std::max(clipped_level_min_, level_ - kClippedLevelStep));
       // Reset the AGC since the level has changed.
       agc_->Reset();
     }
     frames_since_clipped_ = 0;
   }
 }

 void AgcManagerDirect::Process(const int16_t* audio,
                                size_t length,
                                int sample_rate_hz) {
   if (capture_muted_) {
     return;
   }

   if (check_volume_on_next_process_) {
     check_volume_on_next_process_ = false;
     // We have to wait until the first process call to check the volume,
     // because Chromium doesn't guarantee it to be valid any earlier.
     CheckVolumeAndReset();
   }

   agc_->Process(audio, length, sample_rate_hz);

   UpdateGain();
   UpdateCompressor();

   file_postproc_->Write(audio, length);
 }

 void AgcManagerDirect::SetLevel(int new_level) {
   int voe_level = volume_callbacks_->GetMicVolume();
   if (voe_level == 0) {
     RTC_DLOG(LS_INFO)
         << "[agc] VolumeCallbacks returned level=0, taking no action.";
     return;
   }
   if (voe_level < 0 || voe_level > kMaxMicLevel) {
     RTC_LOG(LS_ERROR) << "VolumeCallbacks returned an invalid level="
                       << voe_level;
     return;
   }

   if (voe_level > level_ + kLevelQuantizationSlack ||
       voe_level < level_ - kLevelQuantizationSlack) {
     RTC_DLOG(LS_INFO) << "[agc] Mic volume was manually adjusted. Updating "
                          "stored level from " << level_ << " to " << voe_level;
     level_ = voe_level;
     // Always allow the user to increase the volume.
     if (level_ > max_level_) {
       SetMaxLevel(level_);
     }
     // Take no action in this case, since we can't be sure when the volume
     // was manually adjusted. The compressor will still provide some of the
     // desired gain change.
     agc_->Reset();
     return;
   }

   new_level = std::min(new_level, max_level_);
   if (new_level == level_) {
     return;
   }

   volume_callbacks_->SetMicVolume(new_level);
   RTC_DLOG(LS_INFO) << "[agc] voe_level=" << voe_level << ", "
                     << "level_=" << level_ << ", "
                     << "new_level=" << new_level;
   level_ = new_level;
 }

 void AgcManagerDirect::SetMaxLevel(int level) {
   RTC_DCHECK_GE(level, clipped_level_min_);
   max_level_ = level;
   // Scale the |kSurplusCompressionGain| linearly across the restricted
   // level range.
   max_compression_gain_ =
       kMaxCompressionGain + std::floor((1.f * kMaxMicLevel - max_level_) /
                                            (kMaxMicLevel - clipped_level_min_) *
                                            kSurplusCompressionGain +
                                        0.5f);
   RTC_DLOG(LS_INFO) << "[agc] max_level_=" << max_level_
                     << ", max_compression_gain_=" << max_compression_gain_;
 }

 void AgcManagerDirect::SetCaptureMuted(bool muted) {
   if (capture_muted_ == muted) {
     return;
   }
   capture_muted_ = muted;

   if (!muted) {
     // When we unmute, we should reset things to be safe.
     check_volume_on_next_process_ = true;
   }
 }

 float AgcManagerDirect::voice_probability() {
   return agc_->voice_probability();
 }

 int AgcManagerDirect::CheckVolumeAndReset() {
   int level = volume_callbacks_->GetMicVolume();
   // Reasons for taking action at startup:
   // 1) A person starting a call is expected to be heard.
   // 2) Independent of interpretation of |level| == 0 we should raise it so the
   // AGC can do its job properly.
   if (level == 0 && !startup_) {
     RTC_DLOG(LS_INFO)
         << "[agc] VolumeCallbacks returned level=0, taking no action.";
     return 0;
   }
   if (level < 0 || level > kMaxMicLevel) {
     RTC_LOG(LS_ERROR) << "[agc] VolumeCallbacks returned an invalid level="
                       << level;
     return -1;
   }
   RTC_DLOG(LS_INFO) << "[agc] Initial GetMicVolume()=" << level;

   int minLevel = startup_ ? startup_min_level_ : kMinMicLevel;
   if (level < minLevel) {
     level = minLevel;
     RTC_DLOG(LS_INFO) << "[agc] Initial volume too low, raising to " << level;
     volume_callbacks_->SetMicVolume(level);
   }
   agc_->Reset();
   level_ = level;
   startup_ = false;
   return 0;
 }

 // Requests the RMS error from AGC and distributes the required gain change
 // between the digital compression stage and volume slider. We use the
 // compressor first, providing a slack region around the current slider
 // position to reduce movement.
 //
 // If the slider needs to be moved, we check first if the user has adjusted
 // it, in which case we take no action and cache the updated level.
 void AgcManagerDirect::UpdateGain() {
   int rms_error = 0;
   if (!agc_->GetRmsErrorDb(&rms_error)) {
     // No error update ready.
     return;
   }
   // The compressor will always add at least kMinCompressionGain. In effect,
   // this adjusts our target gain upward by the same amount and rms_error
   // needs to reflect that.
   rms_error += kMinCompressionGain;

   // Handle as much error as possible with the compressor first.
   int raw_compression =
       rtc::SafeClamp(rms_error, kMinCompressionGain, max_compression_gain_);

   // Deemphasize the compression gain error. Move halfway between the current
   // target and the newly received target. This serves to soften perceptible
   // intra-talkspurt adjustments, at the cost of some adaptation speed.
   if ((raw_compression == max_compression_gain_ &&
       target_compression_ == max_compression_gain_ - 1) ||
       (raw_compression == kMinCompressionGain &&
       target_compression_ == kMinCompressionGain + 1)) {
     // Special case to allow the target to reach the endpoints of the
     // compression range. The deemphasis would otherwise halt it at 1 dB shy.
     target_compression_ = raw_compression;
   } else {
     target_compression_ = (raw_compression - target_compression_) / 2
         + target_compression_;
   }

   // Residual error will be handled by adjusting the volume slider. Use the
   // raw rather than deemphasized compression here as we would otherwise
   // shrink the amount of slack the compressor provides.
   const int residual_gain =
       rtc::SafeClamp(rms_error - raw_compression, -kMaxResidualGainChange,
                      kMaxResidualGainChange);
   RTC_DLOG(LS_INFO) << "[agc] rms_error=" << rms_error
                     << ", target_compression=" << target_compression_
                     << ", residual_gain=" << residual_gain;
   if (residual_gain == 0)
     return;

   int old_level = level_;
   SetLevel(LevelFromGainError(residual_gain, level_));
   if (old_level != level_) {
     // level_ was updated by SetLevel; log the new value.
     RTC_HISTOGRAM_COUNTS_LINEAR("WebRTC.Audio.AgcSetLevel", level_, 1,
                                 kMaxMicLevel, 50);
   }
 }

 void AgcManagerDirect::UpdateCompressor() {
   if (compression_ == target_compression_) {
     return;
   }

   // Adapt the compression gain slowly towards the target, in order to avoid
   // highly perceptible changes.
   if (target_compression_ > compression_) {
     compression_accumulator_ += kCompressionGainStep;
   } else {
     compression_accumulator_ -= kCompressionGainStep;
   }

   // The compressor accepts integer gains in dB. Adjust the gain when
   // we've come within half a stepsize of the nearest integer.  (We don't
   // check for equality due to potential floating point imprecision).
   int new_compression = compression_;
   int nearest_neighbor = std::floor(compression_accumulator_ + 0.5);
   if (std::fabs(compression_accumulator_ - nearest_neighbor) <
       kCompressionGainStep / 2) {
     new_compression = nearest_neighbor;
   }

   // Set the new compression gain.
   if (new_compression != compression_) {
     compression_ = new_compression;
     compression_accumulator_ = new_compression;
     if (gctrl_->set_compression_gain_db(compression_) != 0) {
       RTC_LOG(LS_ERROR) << "set_compression_gain_db(" << compression_
                         << ") failed.";
     }
   }
 }

 }  // namespace webrtc
	/*
	* Copyright (c) 2013 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/agc/agc_manager_direct.h"

	#include <cmath>

	#ifdef WEBRTC_AGC_DEBUG_DUMP
	#include <cstdio>
	#endif

	#include "modules/audio_processing/agc/gain_map_internal.h"
	#include "modules/audio_processing/gain_control_impl.h"
	#include "modules/include/module_common_types.h"
	#include "rtc_base/checks.h"
	#include "rtc_base/logging.h"
	#include "rtc_base/numerics/safe_minmax.h"
	#include "system_wrappers/include/metrics.h"

	namespace webrtc {

	namespace {

	// Amount the microphone level is lowered with every clipping event.
	const int kClippedLevelStep = 15;
	// Proportion of clipped samples required to declare a clipping event.
	const float kClippedRatioThreshold = 0.1f;
	// Time in frames to wait after a clipping event before checking again.
	const int kClippedWaitFrames = 300;

	// Amount of error we tolerate in the microphone level (presumably due to OS
	// quantization) before we assume the user has manually adjusted the microphone.
	const int kLevelQuantizationSlack = 25;

	const int kDefaultCompressionGain = 7;
	const int kMaxCompressionGain = 12;
	const int kMinCompressionGain = 2;
	// Controls the rate of compression changes towards the target.
	const float kCompressionGainStep = 0.05f;

	const int kMaxMicLevel = 255;
	static_assert(kGainMapSize > kMaxMicLevel, "gain map too small");
	const int kMinMicLevel = 12;

	// Prevent very large microphone level changes.
	const int kMaxResidualGainChange = 15;

	// Maximum additional gain allowed to compensate for microphone level
	// restrictions from clipping events.
	const int kSurplusCompressionGain = 6;

	int ClampLevel(int mic_level) {
	return rtc::SafeClamp(mic_level, kMinMicLevel, kMaxMicLevel);
	}

	int LevelFromGainError(int gain_error, int level) {
	RTC_DCHECK_GE(level, 0);
	RTC_DCHECK_LE(level, kMaxMicLevel);
	if (gain_error == 0) {
	return level;
	}
	// TODO(ajm): Could be made more efficient with a binary search.
	int new_level = level;
	if (gain_error > 0) {
	while (kGainMap[new_level] - kGainMap[level] < gain_error &&
	new_level < kMaxMicLevel) {
	++new_level;
	}
	} else {
	while (kGainMap[new_level] - kGainMap[level] > gain_error &&
	new_level > kMinMicLevel) {
	--new_level;
	}
	}
	return new_level;
	}

	} // namespace

	// Facility for dumping debug audio files. All methods are no-ops in the
	// default case where WEBRTC_AGC_DEBUG_DUMP is undefined.
	class DebugFile {
	#ifdef WEBRTC_AGC_DEBUG_DUMP
	public:
	explicit DebugFile(const char* filename)
	: file_(fopen(filename, "wb")) {
	RTC_DCHECK(file_);
	}
	~DebugFile() {
	fclose(file_);
	}
	void Write(const int16_t* data, size_t length_samples) {
	fwrite(data, 1, length_samples * sizeof(int16_t), file_);
	}
	private:
	FILE* file_;
	#else
	public:
	explicit DebugFile(const char* filename) {
	}
	~DebugFile() {
	}
	void Write(const int16_t* data, size_t length_samples) {
	}
	#endif // WEBRTC_AGC_DEBUG_DUMP
	};

	AgcManagerDirect::AgcManagerDirect(GainControl* gctrl,
	VolumeCallbacks* volume_callbacks,
	int startup_min_level,
	int clipped_level_min)
	: agc_(new Agc()),
	gctrl_(gctrl),
	volume_callbacks_(volume_callbacks),
	frames_since_clipped_(kClippedWaitFrames),
	level_(0),
	max_level_(kMaxMicLevel),
	max_compression_gain_(kMaxCompressionGain),
	target_compression_(kDefaultCompressionGain),
	compression_(target_compression_),
	compression_accumulator_(compression_),
	capture_muted_(false),
	check_volume_on_next_process_(true), // Check at startup.
	startup_(true),
	startup_min_level_(ClampLevel(startup_min_level)),
	clipped_level_min_(clipped_level_min),
	file_preproc_(new DebugFile("agc_preproc.pcm")),
	file_postproc_(new DebugFile("agc_postproc.pcm")) {}

	AgcManagerDirect::AgcManagerDirect(Agc* agc,
	GainControl* gctrl,
	VolumeCallbacks* volume_callbacks,
	int startup_min_level,
	int clipped_level_min)
	: agc_(agc),
	gctrl_(gctrl),
	volume_callbacks_(volume_callbacks),
	frames_since_clipped_(kClippedWaitFrames),
	level_(0),
	max_level_(kMaxMicLevel),
	max_compression_gain_(kMaxCompressionGain),
	target_compression_(kDefaultCompressionGain),
	compression_(target_compression_),
	compression_accumulator_(compression_),
	capture_muted_(false),
	check_volume_on_next_process_(true), // Check at startup.
	startup_(true),
	startup_min_level_(ClampLevel(startup_min_level)),
	clipped_level_min_(clipped_level_min),
	file_preproc_(new DebugFile("agc_preproc.pcm")),
	file_postproc_(new DebugFile("agc_postproc.pcm")) {}

	AgcManagerDirect::~AgcManagerDirect() {}

	int AgcManagerDirect::Initialize() {
	max_level_ = kMaxMicLevel;
	max_compression_gain_ = kMaxCompressionGain;
	target_compression_ = kDefaultCompressionGain;
	compression_ = target_compression_;
	compression_accumulator_ = compression_;
	capture_muted_ = false;
	check_volume_on_next_process_ = true;
	// TODO(bjornv): Investigate if we need to reset \|startup_\| as well. For
	// example, what happens when we change devices.

	if (gctrl_->set_mode(GainControl::kFixedDigital) != 0) {
	RTC_LOG(LS_ERROR) << "set_mode(GainControl::kFixedDigital) failed.";
	return -1;
	}
	if (gctrl_->set_target_level_dbfs(2) != 0) {
	RTC_LOG(LS_ERROR) << "set_target_level_dbfs(2) failed.";
	return -1;
	}
	if (gctrl_->set_compression_gain_db(kDefaultCompressionGain) != 0) {
	RTC_LOG(LS_ERROR)
	<< "set_compression_gain_db(kDefaultCompressionGain) failed.";
	return -1;
	}
	if (gctrl_->enable_limiter(true) != 0) {
	RTC_LOG(LS_ERROR) << "enable_limiter(true) failed.";
	return -1;
	}
	return 0;
	}

	void AgcManagerDirect::AnalyzePreProcess(int16_t* audio,
	int num_channels,
	size_t samples_per_channel) {
	size_t length = num_channels * samples_per_channel;
	if (capture_muted_) {
	return;
	}

	file_preproc_->Write(audio, length);

	if (frames_since_clipped_ < kClippedWaitFrames) {
	++frames_since_clipped_;
	return;
	}

	// Check for clipped samples, as the AGC has difficulty detecting pitch
	// under clipping distortion. We do this in the preprocessing phase in order
	// to catch clipped echo as well.
	//
	// If we find a sufficiently clipped frame, drop the current microphone level
	// and enforce a new maximum level, dropped the same amount from the current
	// maximum. This harsh treatment is an effort to avoid repeated clipped echo
	// events. As compensation for this restriction, the maximum compression
	// gain is increased, through SetMaxLevel().
	float clipped_ratio = agc_->AnalyzePreproc(audio, length);
	if (clipped_ratio > kClippedRatioThreshold) {
	RTC_DLOG(LS_INFO) << "[agc] Clipping detected. clipped_ratio="
	<< clipped_ratio;
	// Always decrease the maximum level, even if the current level is below
	// threshold.
	SetMaxLevel(std::max(clipped_level_min_, max_level_ - kClippedLevelStep));
	RTC_HISTOGRAM_BOOLEAN("WebRTC.Audio.AgcClippingAdjustmentAllowed",
	level_ - kClippedLevelStep >= clipped_level_min_);
	if (level_ > clipped_level_min_) {
	// Don't try to adjust the level if we're already below the limit. As
	// a consequence, if the user has brought the level above the limit, we
	// will still not react until the postproc updates the level.
	SetLevel(std::max(clipped_level_min_, level_ - kClippedLevelStep));
	// Reset the AGC since the level has changed.
	agc_->Reset();
	}
	frames_since_clipped_ = 0;
	}
	}

	void AgcManagerDirect::Process(const int16_t* audio,
	size_t length,
	int sample_rate_hz) {
	if (capture_muted_) {
	return;
	}

	if (check_volume_on_next_process_) {
	check_volume_on_next_process_ = false;
	// We have to wait until the first process call to check the volume,
	// because Chromium doesn't guarantee it to be valid any earlier.
	CheckVolumeAndReset();
	}

	agc_->Process(audio, length, sample_rate_hz);

	UpdateGain();
	UpdateCompressor();

	file_postproc_->Write(audio, length);
	}

	void AgcManagerDirect::SetLevel(int new_level) {
	int voe_level = volume_callbacks_->GetMicVolume();
	if (voe_level == 0) {
	RTC_DLOG(LS_INFO)
	<< "[agc] VolumeCallbacks returned level=0, taking no action.";
	return;
	}
	if (voe_level < 0 \|\| voe_level > kMaxMicLevel) {
	RTC_LOG(LS_ERROR) << "VolumeCallbacks returned an invalid level="
	<< voe_level;
	return;
	}

	if (voe_level > level_ + kLevelQuantizationSlack \|\|
	voe_level < level_ - kLevelQuantizationSlack) {
	RTC_DLOG(LS_INFO) << "[agc] Mic volume was manually adjusted. Updating "
	"stored level from " << level_ << " to " << voe_level;
	level_ = voe_level;
	// Always allow the user to increase the volume.
	if (level_ > max_level_) {
	SetMaxLevel(level_);
	}
	// Take no action in this case, since we can't be sure when the volume
	// was manually adjusted. The compressor will still provide some of the
	// desired gain change.
	agc_->Reset();
	return;
	}

	new_level = std::min(new_level, max_level_);
	if (new_level == level_) {
	return;
	}

	volume_callbacks_->SetMicVolume(new_level);
	RTC_DLOG(LS_INFO) << "[agc] voe_level=" << voe_level << ", "
	<< "level_=" << level_ << ", "
	<< "new_level=" << new_level;
	level_ = new_level;
	}

	void AgcManagerDirect::SetMaxLevel(int level) {
	RTC_DCHECK_GE(level, clipped_level_min_);
	max_level_ = level;
	// Scale the \|kSurplusCompressionGain\| linearly across the restricted
	// level range.
	max_compression_gain_ =
	kMaxCompressionGain + std::floor((1.f * kMaxMicLevel - max_level_) /
	(kMaxMicLevel - clipped_level_min_) *
	kSurplusCompressionGain +
	0.5f);
	RTC_DLOG(LS_INFO) << "[agc] max_level_=" << max_level_
	<< ", max_compression_gain_=" << max_compression_gain_;
	}

	void AgcManagerDirect::SetCaptureMuted(bool muted) {
	if (capture_muted_ == muted) {
	return;
	}
	capture_muted_ = muted;

	if (!muted) {
	// When we unmute, we should reset things to be safe.
	check_volume_on_next_process_ = true;
	}
	}

	float AgcManagerDirect::voice_probability() {
	return agc_->voice_probability();
	}

	int AgcManagerDirect::CheckVolumeAndReset() {
	int level = volume_callbacks_->GetMicVolume();
	// Reasons for taking action at startup:
	// 1) A person starting a call is expected to be heard.
	// 2) Independent of interpretation of \|level\| == 0 we should raise it so the
	// AGC can do its job properly.
	if (level == 0 && !startup_) {
	RTC_DLOG(LS_INFO)
	<< "[agc] VolumeCallbacks returned level=0, taking no action.";
	return 0;
	}
	if (level < 0 \|\| level > kMaxMicLevel) {
	RTC_LOG(LS_ERROR) << "[agc] VolumeCallbacks returned an invalid level="
	<< level;
	return -1;
	}
	RTC_DLOG(LS_INFO) << "[agc] Initial GetMicVolume()=" << level;

	int minLevel = startup_ ? startup_min_level_ : kMinMicLevel;
	if (level < minLevel) {
	level = minLevel;
	RTC_DLOG(LS_INFO) << "[agc] Initial volume too low, raising to " << level;
	volume_callbacks_->SetMicVolume(level);
	}
	agc_->Reset();
	level_ = level;
	startup_ = false;
	return 0;
	}

	// Requests the RMS error from AGC and distributes the required gain change
	// between the digital compression stage and volume slider. We use the
	// compressor first, providing a slack region around the current slider
	// position to reduce movement.
	//
	// If the slider needs to be moved, we check first if the user has adjusted
	// it, in which case we take no action and cache the updated level.
	void AgcManagerDirect::UpdateGain() {
	int rms_error = 0;
	if (!agc_->GetRmsErrorDb(&rms_error)) {
	// No error update ready.
	return;
	}
	// The compressor will always add at least kMinCompressionGain. In effect,
	// this adjusts our target gain upward by the same amount and rms_error
	// needs to reflect that.
	rms_error += kMinCompressionGain;

	// Handle as much error as possible with the compressor first.
	int raw_compression =
	rtc::SafeClamp(rms_error, kMinCompressionGain, max_compression_gain_);

	// Deemphasize the compression gain error. Move halfway between the current
	// target and the newly received target. This serves to soften perceptible
	// intra-talkspurt adjustments, at the cost of some adaptation speed.
	if ((raw_compression == max_compression_gain_ &&
	target_compression_ == max_compression_gain_ - 1) \|\|
	(raw_compression == kMinCompressionGain &&
	target_compression_ == kMinCompressionGain + 1)) {
	// Special case to allow the target to reach the endpoints of the
	// compression range. The deemphasis would otherwise halt it at 1 dB shy.
	target_compression_ = raw_compression;
	} else {
	target_compression_ = (raw_compression - target_compression_) / 2
	+ target_compression_;
	}

	// Residual error will be handled by adjusting the volume slider. Use the
	// raw rather than deemphasized compression here as we would otherwise
	// shrink the amount of slack the compressor provides.
	const int residual_gain =
	rtc::SafeClamp(rms_error - raw_compression, -kMaxResidualGainChange,
	kMaxResidualGainChange);
	RTC_DLOG(LS_INFO) << "[agc] rms_error=" << rms_error
	<< ", target_compression=" << target_compression_
	<< ", residual_gain=" << residual_gain;
	if (residual_gain == 0)
	return;

	int old_level = level_;
	SetLevel(LevelFromGainError(residual_gain, level_));
	if (old_level != level_) {
	// level_ was updated by SetLevel; log the new value.
	RTC_HISTOGRAM_COUNTS_LINEAR("WebRTC.Audio.AgcSetLevel", level_, 1,
	kMaxMicLevel, 50);
	}
	}

	void AgcManagerDirect::UpdateCompressor() {
	if (compression_ == target_compression_) {
	return;
	}

	// Adapt the compression gain slowly towards the target, in order to avoid
	// highly perceptible changes.
	if (target_compression_ > compression_) {
	compression_accumulator_ += kCompressionGainStep;
	} else {
	compression_accumulator_ -= kCompressionGainStep;
	}

	// The compressor accepts integer gains in dB. Adjust the gain when
	// we've come within half a stepsize of the nearest integer. (We don't
	// check for equality due to potential floating point imprecision).
	int new_compression = compression_;
	int nearest_neighbor = std::floor(compression_accumulator_ + 0.5);
	if (std::fabs(compression_accumulator_ - nearest_neighbor) <
	kCompressionGainStep / 2) {
	new_compression = nearest_neighbor;
	}

	// Set the new compression gain.
	if (new_compression != compression_) {
	compression_ = new_compression;
	compression_accumulator_ = new_compression;
	if (gctrl_->set_compression_gain_db(compression_) != 0) {
	RTC_LOG(LS_ERROR) << "set_compression_gain_db(" << compression_
	<< ") failed.";
	}
	}
	}

	} // namespace webrtc