media/base/audio_renderer_mixer.h

   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 #include <string>
  10
  11 #include "base/synchronization/lock.h"
  12 #include "base/time/time.h"
  13 #include "media/base/audio_converter.h"
  14 #include "media/base/audio_renderer_sink.h"
  15
  16 namespace media {
  17
  18 // Mixes a set of AudioConverter::InputCallbacks into a single output stream
  19 // which is funneled into a single shared AudioRendererSink; saving a bundle
  20 // on renderer side resources.
  21 class MEDIA_EXPORT AudioRendererMixer
  22     : NON_EXPORTED_BASE(public AudioRendererSink::RenderCallback) {
  23  public:
  24   AudioRendererMixer(const AudioParameters& input_params,
  25                      const AudioParameters& output_params,
  26                      const scoped_refptr<AudioRendererSink>& sink);
  27   ~AudioRendererMixer() override;
  28
  29   // Add or remove a mixer input from mixing; called by AudioRendererMixerInput.
  30   void AddMixerInput(AudioConverter::InputCallback* input);
  31   void RemoveMixerInput(AudioConverter::InputCallback* input);
  32
  33   // Since errors may occur even when no inputs are playing, an error callback
  34   // must be registered separately from adding a mixer input.  The same callback
  35   // must be given to both the functions.
  36   void AddErrorCallback(const base::Closure& error_cb);
  37   void RemoveErrorCallback(const base::Closure& error_cb);
  38
  39   void set_pause_delay_for_testing(base::TimeDelta delay) {
  40     pause_delay_ = delay;
  41   }
  42
  43   // TODO(guidou): remove this method. The output device of a mixer should
  44   // never be switched, as it may result in a discrepancy between the output
  45   // parameters of the new device and the output parameters with which the
  46   // mixer was initialized. See crbug.com/506507
  47   OutputDevice* GetOutputDevice();
  48
  49  private:
  50   // AudioRendererSink::RenderCallback implementation.
  51   int Render(AudioBus* audio_bus, int audio_delay_milliseconds) override;
  52   void OnRenderError() override;
  53
  54   // Output sink for this mixer.
  55   scoped_refptr<AudioRendererSink> audio_sink_;
  56
  57   // ---------------[ All variables below protected by |lock_| ]---------------
  58   base::Lock lock_;
  59
  60   // List of error callbacks used by this mixer.
  61   typedef std::list<base::Closure> ErrorCallbackList;
  62   ErrorCallbackList error_callbacks_;
  63
  64   // Handles mixing and resampling between input and output parameters.
  65   AudioConverter audio_converter_;
  66
  67   // Handles physical stream pause when no inputs are playing.  For latency
  68   // reasons we don't want to immediately pause the physical stream.
  69   base::TimeDelta pause_delay_;
  70   base::TimeTicks last_play_time_;
  71   bool playing_;
  72
  73   DISALLOW_COPY_AND_ASSIGN(AudioRendererMixer);
  74 };
  75
  76 }  // namespace media
  77
  78 #endif  // MEDIA_BASE_AUDIO_RENDERER_MIXER_H_