Less lock acquisitions for AudioMixer.

webrtc/modules/audio_mixer/audio_mixer_impl.cc

Index: webrtc/modules/audio_mixer/audio_mixer_impl.cc
diff --git a/webrtc/modules/audio_mixer/audio_mixer_impl.cc b/webrtc/modules/audio_mixer/audio_mixer_impl.cc
index 5a8d1eb7645705113dc3155565668b198a6bbeb3..67def0ee608f9c1ae7c5848bf8961e3d86fb3aa3 100644
--- a/webrtc/modules/audio_mixer/audio_mixer_impl.cc
+++ b/webrtc/modules/audio_mixer/audio_mixer_impl.cc
@@ -13,6 +13,7 @@
 #include <algorithm>
 #include <functional>
 
+#include "webrtc/base/thread_annotations.h"
 #include "webrtc/modules/audio_mixer/audio_frame_manipulator.h"
 #include "webrtc/modules/audio_mixer/audio_mixer_defines.h"
 #include "webrtc/modules/audio_processing/include/audio_processing.h"
@@ -147,10 +148,6 @@ bool AudioMixerImpl::Init() {
   if (crit_.get() == NULL)
     return false;
 
-  cb_crit_.reset(CriticalSectionWrapper::CreateCriticalSection());
-  if (cb_crit_.get() == NULL)
-    return false;
-
   Config config;
   config.Set<ExperimentalAgc>(new ExperimentalAgc(false));
   limiter_.reset(AudioProcessing::Create(config));
@@ -188,37 +185,28 @@ void AudioMixerImpl::Mix(int sample_rate,
                          AudioFrame* audio_frame_for_mixing) {
   RTC_DCHECK(number_of_channels == 1 || number_of_channels == 2);
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
-  AudioFrameList mixList;
-  AudioFrameList additionalFramesList;
   std::map<int, MixerAudioSource*> mixedAudioSourcesMap;
-  {
-    CriticalSectionScoped cs(cb_crit_.get());
-    Frequency mixing_frequency;
-
-    switch (sample_rate) {
-      case 8000:
-        mixing_frequency = kNbInHz;
-        break;
-      case 16000:
-        mixing_frequency = kWbInHz;
-        break;
-      case 32000:
-        mixing_frequency = kSwbInHz;
-        break;
-      case 48000:
-        mixing_frequency = kFbInHz;
-        break;
-      default:
-        RTC_NOTREACHED();
-        return;
-    }
 
-    if (OutputFrequency() != mixing_frequency) {
-      SetOutputFrequency(mixing_frequency);
-    }
+  if (sample_rate != kNbInHz && sample_rate != kWbInHz &&
+      sample_rate != kSwbInHz && sample_rate != kFbInHz) {
+    WEBRTC_TRACE(kTraceError, kTraceAudioMixerServer, id_,
+                 "Invalid frequency: %d", sample_rate);
+    RTC_NOTREACHED();
+    return;
+  }
+
+  if (OutputFrequency() != sample_rate) {
+    SetOutputFrequency(static_cast<Frequency>(sample_rate));
+  }
 
+  AudioFrameList mixList;
+  AudioFrameList additionalFramesList;
+  int num_mixed_audio_sources;
+  {
+    CriticalSectionScoped cs(crit_.get());
     mixList = UpdateToMix(kMaximumAmountOfMixedAudioSources);
     GetAdditionalAudio(&additionalFramesList);
+    num_mixed_audio_sources = num_mixed_audio_sources_;
   }
 
   for (FrameAndMuteInfo& frame_and_mute : mixList) {
@@ -234,24 +222,19 @@ void AudioMixerImpl::Mix(int sample_rate,
 
   time_stamp_ += static_cast<uint32_t>(sample_size_);
 
-  use_limiter_ = num_mixed_audio_sources_ > 1;
+  use_limiter_ = num_mixed_audio_sources > 1;
 
   // We only use the limiter if it supports the output sample rate and
   // we're actually mixing multiple streams.
   MixFromList(audio_frame_for_mixing, mixList, id_, use_limiter_);
-
-  {
-    CriticalSectionScoped cs(crit_.get());
-    MixAnonomouslyFromList(audio_frame_for_mixing, additionalFramesList);
-
-    if (audio_frame_for_mixing->samples_per_channel_ == 0) {
-      // Nothing was mixed, set the audio samples to silence.
-      audio_frame_for_mixing->samples_per_channel_ = sample_size_;
-      audio_frame_for_mixing->Mute();
-    } else {
-      // Only call the limiter if we have something to mix.
-      LimitMixedAudio(audio_frame_for_mixing);
-    }
+  MixAnonomouslyFromList(audio_frame_for_mixing, additionalFramesList);
+  if (audio_frame_for_mixing->samples_per_channel_ == 0) {
+    // Nothing was mixed, set the audio samples to silence.
+    audio_frame_for_mixing->samples_per_channel_ = sample_size_;
+    audio_frame_for_mixing->Mute();
+  } else {
+    // Only call the limiter if we have something to mix.
+    LimitMixedAudio(audio_frame_for_mixing);
   }
 
   // Pass the final result to the level indicator.
@@ -261,8 +244,7 @@ void AudioMixerImpl::Mix(int sample_rate,
 }
 
 int32_t AudioMixerImpl::SetOutputFrequency(const Frequency& frequency) {
-  CriticalSectionScoped cs(crit_.get());
-
+  RTC_DCHECK(thread_checker_.CalledOnValidThread());
   output_frequency_ = frequency;
   sample_size_ =
       static_cast<size_t>((output_frequency_ * kFrameDurationInMs) / 1000);
@@ -271,7 +253,7 @@ int32_t AudioMixerImpl::SetOutputFrequency(const Frequency& frequency) {
 }
 
 AudioMixer::Frequency AudioMixerImpl::OutputFrequency() const {
-  CriticalSectionScoped cs(crit_.get());
+  RTC_DCHECK(thread_checker_.CalledOnValidThread());
   return output_frequency_;
 }
 
@@ -282,9 +264,8 @@ int32_t AudioMixerImpl::SetMixabilityStatus(MixerAudioSource* audio_source,
     // audio source is in the _audioSourceList if it is being mixed.
     SetAnonymousMixabilityStatus(audio_source, false);
   }
-  size_t numMixedAudioSources;
   {
-    CriticalSectionScoped cs(cb_crit_.get());
+    CriticalSectionScoped cs(crit_.get());
     const bool isMixed = IsAudioSourceInList(*audio_source, audio_source_list_);
     // API must be called with a new state.
     if (!(mixable ^ isMixed)) {
@@ -309,27 +290,22 @@ int32_t AudioMixerImpl::SetMixabilityStatus(MixerAudioSource* audio_source,
     if (numMixedNonAnonymous > kMaximumAmountOfMixedAudioSources) {
       numMixedNonAnonymous = kMaximumAmountOfMixedAudioSources;
     }
-    numMixedAudioSources =
+    num_mixed_audio_sources_ =
         numMixedNonAnonymous + additional_audio_source_list_.size();
   }
-  // A MixerAudioSource was added or removed. Make sure the scratch
-  // buffer is updated if necessary.
-  // Note: The scratch buffer may only be updated in Process().
-  CriticalSectionScoped cs(crit_.get());
-  num_mixed_audio_sources_ = numMixedAudioSources;
   return 0;
 }
 
 bool AudioMixerImpl::MixabilityStatus(
     const MixerAudioSource& audio_source) const {
-  CriticalSectionScoped cs(cb_crit_.get());
+  CriticalSectionScoped cs(crit_.get());
   return IsAudioSourceInList(audio_source, audio_source_list_);
 }
 
 int32_t AudioMixerImpl::SetAnonymousMixabilityStatus(
     MixerAudioSource* audio_source,
     bool anonymous) {
-  CriticalSectionScoped cs(cb_crit_.get());
+  CriticalSectionScoped cs(crit_.get());
   if (IsAudioSourceInList(*audio_source, additional_audio_source_list_)) {
     if (anonymous) {
       return 0;
@@ -363,7 +339,7 @@ int32_t AudioMixerImpl::SetAnonymousMixabilityStatus(
 
 bool AudioMixerImpl::AnonymousMixabilityStatus(
     const MixerAudioSource& audio_source) const {
-  CriticalSectionScoped cs(cb_crit_.get());
+  CriticalSectionScoped cs(crit_.get());
   return IsAudioSourceInList(audio_source, additional_audio_source_list_);
 }