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
  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   ~AudioRendererMixer() override;
  27
  28   // Add or remove a mixer input from mixing; called by AudioRendererMixerInput.
  29   void AddMixerInput(AudioConverter::InputCallback* input);
  30   void RemoveMixerInput(AudioConverter::InputCallback* input);
  31
  32   // Since errors may occur even when no inputs are playing, an error callback
  33   // must be registered separately from adding a mixer input.  The same callback
  34   // must be given to both the functions.
  35   void AddErrorCallback(const base::Closure& error_cb);
  36   void RemoveErrorCallback(const base::Closure& error_cb);
  37
  38   void set_pause_delay_for_testing(base::TimeDelta delay) {
  39     pause_delay_ = delay;
  40   }
  41
  42  private:
  43   // AudioRendererSink::RenderCallback implementation.
  44   int Render(AudioBus* audio_bus, int audio_delay_milliseconds) override;
  45   void OnRenderError() override;
  46
  47   // Output sink for this mixer.
  48   scoped_refptr<AudioRendererSink> audio_sink_;
  49
  50   // ---------------[ All variables below protected by |lock_| ]---------------
  51   base::Lock lock_;
  52
  53   // List of error callbacks used by this mixer.
  54   typedef std::list<base::Closure> ErrorCallbackList;
  55   ErrorCallbackList error_callbacks_;
  56
  57   // Handles mixing and resampling between input and output parameters.
  58   AudioConverter audio_converter_;
  59
  60   // Handles physical stream pause when no inputs are playing.  For latency
  61   // reasons we don't want to immediately pause the physical stream.
  62   base::TimeDelta pause_delay_;
  63   base::TimeTicks last_play_time_;
  64   bool playing_;
  65
  66   DISALLOW_COPY_AND_ASSIGN(AudioRendererMixer);
  67 };
  68
  69 }  // namespace media
  70
  71 #endif  // MEDIA_BASE_AUDIO_RENDERER_MIXER_H_