Injectable output rate calculater for AudioMixer.

webrtc/modules/audio_mixer/audio_mixer_impl.h

Index: webrtc/modules/audio_mixer/audio_mixer_impl.h
diff --git a/webrtc/modules/audio_mixer/audio_mixer_impl.h b/webrtc/modules/audio_mixer/audio_mixer_impl.h
index af83367fc4ab10057c351c2d1a002220e5a940cc..0da06e7e77c8db7878ed18747751ab5bd0f8b699 100644
--- a/webrtc/modules/audio_mixer/audio_mixer_impl.h
+++ b/webrtc/modules/audio_mixer/audio_mixer_impl.h
@@ -18,6 +18,7 @@
 #include "webrtc/base/scoped_ref_ptr.h"
 #include "webrtc/base/thread_annotations.h"
 #include "webrtc/base/race_checker.h"
+#include "webrtc/modules/audio_mixer/output_rate_calculator.h"
 #include "webrtc/modules/audio_processing/include/audio_processing.h"
 #include "webrtc/modules/include/module_common_types.h"
 #include "webrtc/system_wrappers/include/critical_section_wrapper.h"
@@ -45,9 +46,10 @@ class AudioMixerImpl : public AudioMixer {
   // AudioProcessing only accepts 10 ms frames.
   static const int kFrameDurationInMs = 10;
   static const int kMaximumAmountOfMixedAudioSources = 3;
-  static const int kDefaultFrequency = 48000;
 
   static rtc::scoped_refptr<AudioMixerImpl> Create();
+  static rtc::scoped_refptr<AudioMixerImpl> CreateWithOutputRateCalculator(
+      std::unique_ptr<OutputRateCalculator> output_rate_calculator);
 
   ~AudioMixerImpl() override;
 
@@ -64,11 +66,12 @@ class AudioMixerImpl : public AudioMixer {
   bool GetAudioSourceMixabilityStatusForTest(Source* audio_source) const;
 
  protected:
-  explicit AudioMixerImpl(std::unique_ptr<AudioProcessing> limiter);
+  AudioMixerImpl(std::unique_ptr<AudioProcessing> limiter,
+                 std::unique_ptr<OutputRateCalculator> output_rate_calculator);
 
  private:
   // Set/get mix frequency
-  void SetOutputFrequency(int frequency);
+  void SetOutputFrequency();

[ivoc, 2016/12/08 10:09:47]

I think this function should be renamed, the current name implies that it is a
setter, but it's confusing because it doesn't take an argument. Something like
CalculateOutputFrequency() would be better IMO.

   int OutputFrequency() const;
 
   // Compute what audio sources to mix from audio_source_list_. Ramp
@@ -91,6 +94,7 @@ class AudioMixerImpl : public AudioMixer {
   rtc::CriticalSection crit_;
   rtc::RaceChecker race_checker_;
 
+  std::unique_ptr<OutputRateCalculator> output_rate_calculator_;
   // The current sample frequency and sample size when mixing.
   int output_frequency_ GUARDED_BY(race_checker_);
   size_t sample_size_ GUARDED_BY(race_checker_);