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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef MEDIA_BASE_AUDIO_RENDERER_MIXER_H_
      6 #define MEDIA_BASE_AUDIO_RENDERER_MIXER_H_
      7 
      8 #include <map>
      9 
     10 #include "base/synchronization/lock.h"
     11 #include "base/time/time.h"
     12 #include "media/base/audio_converter.h"
     13 #include "media/base/audio_renderer_sink.h"
     14 
     15 namespace media {
     16 
     17 // Mixes a set of AudioConverter::InputCallbacks into a single output stream
     18 // which is funneled into a single shared AudioRendererSink; saving a bundle
     19 // on renderer side resources.
     20 class MEDIA_EXPORT AudioRendererMixer
     21     : NON_EXPORTED_BASE(public AudioRendererSink::RenderCallback) {
     22  public:
     23   AudioRendererMixer(const AudioParameters& input_params,
     24                      const AudioParameters& output_params,
     25                      const scoped_refptr<AudioRendererSink>& sink);
     26   virtual ~AudioRendererMixer();
     27 
     28   // Add or remove a mixer input from mixing; called by AudioRendererMixerInput.
     29   void AddMixerInput(AudioConverter::InputCallback* input,
     30                      const base::Closure& error_cb);
     31   void RemoveMixerInput(AudioConverter::InputCallback* input);
     32 
     33   void set_pause_delay_for_testing(base::TimeDelta delay) {
     34     pause_delay_ = delay;
     35   }
     36 
     37  private:
     38   // AudioRendererSink::RenderCallback implementation.
     39   virtual int Render(AudioBus* audio_bus,
     40                      int audio_delay_milliseconds) OVERRIDE;
     41   virtual void OnRenderError() OVERRIDE;
     42 
     43   // Output sink for this mixer.
     44   scoped_refptr<AudioRendererSink> audio_sink_;
     45 
     46   // Set of mixer inputs to be mixed by this mixer.  Access is thread-safe
     47   // through |mixer_inputs_lock_|.
     48   typedef std::map<AudioConverter::InputCallback*, base::Closure>
     49       AudioRendererMixerInputSet;
     50   AudioRendererMixerInputSet mixer_inputs_;
     51   base::Lock mixer_inputs_lock_;
     52 
     53   // Handles mixing and resampling between input and output parameters.
     54   AudioConverter audio_converter_;
     55 
     56   // Handles physical stream pause when no inputs are playing.  For latency
     57   // reasons we don't want to immediately pause the physical stream.
     58   base::TimeDelta pause_delay_;
     59   base::TimeTicks last_play_time_;
     60   bool playing_;
     61 
     62   DISALLOW_COPY_AND_ASSIGN(AudioRendererMixer);
     63 };
     64 
     65 }  // namespace media
     66 
     67 #endif  // MEDIA_BASE_AUDIO_RENDERER_MIXER_H_
     68