MediaRecorder: support sampling rate adaption in AudioTrackRecorder

content/renderer/media/audio_track_recorder.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_MEDIA_AUDIO_TRACK_RECORDER_H_
 #define CONTENT_RENDERER_MEDIA_AUDIO_TRACK_RECORDER_H_
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_checker.h"
 #include "base/time/time.h"
 #include "content/public/renderer/media_stream_audio_sink.h"
 #include "third_party/WebKit/public/platform/WebMediaStreamTrack.h"
 
 namespace media {
 class AudioBus;
+class AudioParameters;
 }  // namespace media
 
 namespace content {
 
 // AudioTrackRecorder is a MediaStreamAudioSink that encodes the audio buses
 // received from a Stream Audio Track. The class is constructed on a
 // single thread (the main Render thread) but can recieve MediaStreamAudioSink-
 // related calls on a different "live audio" thread (referred to internally as
 // the "capture thread"). It owns an internal thread to use for encoding, on
 // which lives an AudioEncoder (a private nested class of ATR) with its own
@@ skipping 10 matching lines @@
                      const OnEncodedAudioCB& on_encoded_audio_cb,
                      int32_t bits_per_second);
   ~AudioTrackRecorder() override;
 
   // Implement MediaStreamAudioSink.
   void OnSetFormat(const media::AudioParameters& params) override;
   void OnData(const media::AudioBus& audio_bus,
               base::TimeTicks capture_time) override;
 
  private:
-  friend class AudioTrackRecorderTest;
-  class AudioParameters;
-
   // Forward declaration of nested class for handling encoding.
   // See the implementation file for details.
   class AudioEncoder;
 
-  // Returns the Opus buffer duration in milliseconds, or zero if none will work
-  // for the given |sample_rate|.
-  static int GetOpusBufferDuration(int sample_rate);
-
   // Used to check that we are destroyed on the same thread we were created on.
   base::ThreadChecker main_render_thread_checker_;
 
   // Used to check that MediaStreamAudioSink's methods are called on the
   // capture audio thread.
   base::ThreadChecker capture_thread_checker_;
 
   // We need to hold on to the Blink track to remove ourselves on destruction.
   const blink::WebMediaStreamTrack track_;
 
   // Thin wrapper around OpusEncoder.
   // |encoder_| should be initialized before |encoder_thread_| such that
   // |encoder_thread_| is destructed first. This, combined with all
   // AudioEncoder work (aside from construction and destruction) happening on
   // |encoder_thread_|, should allow us to be sure that all AudioEncoder work is
   // done by the time we destroy it on ATR's thread.
   const scoped_refptr<AudioEncoder> encoder_;
   // The thread on which |encoder_| works.
   base::Thread encoder_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioTrackRecorder);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_AUDIO_TRACK_RECORDER_H_