MuteSource Audio During Full Screen Cast

media/audio/cras/cras_input.cc

Index: media/audio/cras/cras_input.cc
diff --git a/media/audio/cras/cras_input.cc b/media/audio/cras/cras_input.cc
index 0c24be94cafc50e7a0856182166973be986e178e..2ea4521889c15230f78021b60c5eb4b9025e5a1c 100644
--- a/media/audio/cras/cras_input.cc
+++ b/media/audio/cras/cras_input.cc
@@ -27,8 +27,11 @@ CrasInputStream::CrasInputStream(const AudioParameters& params,
       stream_id_(0),
       stream_direction_(CRAS_STREAM_INPUT),
       pin_device_(NO_DEVICE),
-      is_loopback_(device_id ==
-                   AudioDeviceDescription::kLoopbackInputDeviceId) {
+      is_loopback_(
+          device_id == AudioDeviceDescription::kLoopbackInputDeviceId ||
+          device_id == AudioDeviceDescription::kLoopbackWithMuteDeviceId),
+      mute_system_audio_(device_id ==
+                         AudioDeviceDescription::kLoopbackWithMuteDeviceId) {
   DCHECK(audio_manager_);
   audio_bus_ = AudioBus::Create(params_);
 }
@@ -93,6 +96,8 @@ bool CrasInputStream::Open() {
       client_ = NULL;
       return false;
     }
+    if (mute_system_audio_)
+      cras_client_set_system_mute(client_, 1);

[miu, 2016/07/19 01:09:44]

What if the system audio was already muted? Perhaps you should call
cras_client_get_system_mute, stash that away, and then mute system audio. Then
later, in Stop(), restore the original mute state.

Same applies to the Win platform code changes...

[qiangchen, 2016/07/20 22:13:22]

Done.

     pin_device_ = cras_client_get_first_dev_type_idx(client_,
         CRAS_NODE_TYPE_POST_MIX_PRE_DSP, CRAS_STREAM_INPUT);
     if (pin_device_ < 0) {
@@ -231,6 +236,10 @@ void CrasInputStream::Stop() {
   if (!callback_ || !started_)
     return;
 
+  if (mute_system_audio_) {
+    cras_client_set_system_mute(client_, 0);
+  }
+
   StopAgc();
 
   // Removing the stream from the client stops audio.