Allow audio system to handle synchronized low-latency audio I/O

media/base/audio_renderer_sink.h

Index: media/base/audio_renderer_sink.h
===================================================================
--- media/base/audio_renderer_sink.h	(revision 155437)
+++ media/base/audio_renderer_sink.h	(working copy)
@@ -27,6 +27,11 @@
     // number of frames filled.
     virtual int Render(AudioBus* audio_bus, int audio_delay_milliseconds) = 0;
 
+    // Synchronized audio I/O - see InitializeIO() below.
+    virtual void RenderIO(AudioBus* audio_input_data,

[scherkus (not reviewing), 2012/09/10 11:46:32]

nit: most other code has these params as "source / dest" -- here they are
audio_input_data / audio_bus

which one should it be? :)

[Chris Rogers, 2012/09/10 19:21:38]

Fixed to be more consistent:
I'm going to go with "source" and "dest" because I think they're more
descriptive than names like "audio_bus".  I would also be fine with "source_bus"
and "dest_bus", but just wanted to keep things simpler.

+                          AudioBus* audio_bus,
+                          int audio_delay_milliseconds) {}
+
     // Signals an error has occurred.
     virtual void OnRenderError() = 0;
 
@@ -39,6 +44,17 @@
   virtual void Initialize(const AudioParameters& params,
                           RenderCallback* callback) = 0;
 
+  // InitializeIO() may be called instead of Initialize() for clients who wish
+  // to have synchronized input and output.  |input_channels| specifies the
+  // number of input channels which will be at the same sample-rate
+  // and buffer-size as the output as specified in |params|.
+  // The callback's RenderIO() method will be called instead of Render(),
+  // providing the synchronized input data at the same time as when new
+  // output data is to be rendered.
+  virtual void InitializeIO(const AudioParameters& params,
+                            int input_channels,
+                            RenderCallback* callback) {}
+
   // Starts audio playback.
   virtual void Start() = 0;