Handle audio device changes on Windows.

media/audio/audio_manager_base.cc

Index: media/audio/audio_manager_base.cc
diff --git a/media/audio/audio_manager_base.cc b/media/audio/audio_manager_base.cc
index 09e2b05d1f89316e07fbed542546c39b2e847d1e..6eb7439b2745382c20cf223a789cbd693206a6c5 100644
--- a/media/audio/audio_manager_base.cc
+++ b/media/audio/audio_manager_base.cc
@@ -172,41 +172,53 @@ AudioOutputStream* AudioManagerBase::MakeAudioOutputStreamProxy(
 #else
   DCHECK(GetMessageLoop()->BelongsToCurrentThread());
 
-  AudioOutputDispatchersMap::iterator it = output_dispatchers_.find(params);
+  bool use_audio_output_resampler =
+      !CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kDisableAudioOutputResampler) &&
+      params.format() == AudioParameters::AUDIO_PCM_LOW_LATENCY;
+
+  // If we're not using AudioOutputResampler our output parameters are the same
+  // as our input parameters.
+  AudioParameters output_params = params;
+  if (use_audio_output_resampler) {
+    output_params = GetPreferredLowLatencyOutputStreamParameters(params);
+
+    // Ensure we only pass on valid output parameters.
+    if (!output_params.IsValid()) {
+      // We've received invalid audio output parameters, so switch to a mock
+      // output device based on the input parameters.  This may happen if the OS
+      // provided us junk values for the hardware configuration.
+      LOG(ERROR) << "Invalid audio output parameters received; using fake "
+                 << "audio path. Channels: " << output_params.channels() << ", "
+                 << "Sample Rate: " << output_params.sample_rate() << ", "
+                 << "Bits Per Sample: " << output_params.bits_per_sample()
+                 << ", Frames Per Buffer: "
+                 << output_params.frames_per_buffer();
+
+      // Tell the AudioManager to create a fake output device.
+      output_params = AudioParameters(
+          AudioParameters::AUDIO_FAKE, params.channel_layout(),
+          params.sample_rate(), params.bits_per_sample(),
+          params.frames_per_buffer());
+    }
+  }
+
+  std::pair<AudioParameters, AudioParameters> dispatcher_key =
+      std::make_pair(params, output_params);
+  AudioOutputDispatchersMap::iterator it =
+      output_dispatchers_.find(dispatcher_key);
   if (it != output_dispatchers_.end())
     return new AudioOutputProxy(it->second);
 
   base::TimeDelta close_delay =
       base::TimeDelta::FromSeconds(kStreamCloseDelaySeconds);
 
-  const CommandLine* cmd_line = CommandLine::ForCurrentProcess();
-  if (!cmd_line->HasSwitch(switches::kDisableAudioOutputResampler) &&
-      params.format() == AudioParameters::AUDIO_PCM_LOW_LATENCY) {
-    AudioParameters output_params =
-        GetPreferredLowLatencyOutputStreamParameters(params);
-
-    // Ensure we only pass on valid output parameters.
-    if (output_params.IsValid()) {
-      scoped_refptr<AudioOutputDispatcher> dispatcher =
-          new AudioOutputResampler(this, params, output_params, close_delay);
-      output_dispatchers_[params] = dispatcher;
-      return new AudioOutputProxy(dispatcher);
-    }
-
-    // We've received invalid audio output parameters, so switch to a mock
-    // output device based on the input parameters.  This may happen if the OS
-    // provided us junk values for the hardware configuration.
-    LOG(ERROR) << "Invalid audio output parameters received; using fake audio "
-               << "path. Channels: " << output_params.channels() << ", "
-               << "Sample Rate: " << output_params.sample_rate() << ", "
-               << "Bits Per Sample: " << output_params.bits_per_sample()
-               << ", Frames Per Buffer: " << output_params.frames_per_buffer();
-
-    // Passing AUDIO_FAKE tells the AudioManager to create a fake output device.
-    output_params = AudioParameters(
-        AudioParameters::AUDIO_FAKE, params.channel_layout(),
-        params.sample_rate(), params.bits_per_sample(),
-        params.frames_per_buffer());
+  if (use_audio_output_resampler &&
+      output_params.format() != AudioParameters::AUDIO_FAKE) {

[scherkus (not reviewing), 2012/10/22 23:51:05]

sanity q: do we want to explicitly handle the AUDIO_FAKE case?

For example, today it would get used w/ the audio mixer if it was enabled.

[DaleCurtis, 2012/10/23 01:49:42]

That'd be okay and probably even preferable since we'd then only spin up a
single fake audio output stream instead of a bunch of them.  For
AudioOutputResampler though it doesn't make sense since it'd just be additional
overhead.

+    scoped_refptr<AudioOutputDispatcher> dispatcher =
+        new AudioOutputResampler(this, params, output_params, close_delay);
+    output_dispatchers_[dispatcher_key] = dispatcher;
+    return new AudioOutputProxy(dispatcher);
   }
 
 #if defined(ENABLE_AUDIO_MIXER)
@@ -216,14 +228,14 @@ AudioOutputStream* AudioManagerBase::MakeAudioOutputStreamProxy(
   if (cmd_line->HasSwitch(switches::kEnableAudioMixer)) {
     scoped_refptr<AudioOutputDispatcher> dispatcher =
         new AudioOutputMixer(this, params, close_delay);
-    output_dispatchers_[params] = dispatcher;
+    output_dispatchers_[dispatcher_key] = dispatcher;
     return new AudioOutputProxy(dispatcher);
   }
 #endif
 
   scoped_refptr<AudioOutputDispatcher> dispatcher =
       new AudioOutputDispatcherImpl(this, params, close_delay);
-  output_dispatchers_[params] = dispatcher;
+  output_dispatchers_[dispatcher_key] = dispatcher;
   return new AudioOutputProxy(dispatcher);
 #endif  // defined(OS_IOS)
 }