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..af63eabbe30536e3977b5a90afb761ffb983f547 100644
--- a/media/audio/cras/cras_input.cc
+++ b/media/audio/cras/cras_input.cc
@@ -27,8 +27,12 @@ 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),
+      mute_done_(false) {
   DCHECK(audio_manager_);
   audio_bus_ = AudioBus::Create(params_);
 }
@@ -93,6 +97,12 @@ bool CrasInputStream::Open() {
       client_ = NULL;
       return false;
     }
+
+    if (mute_system_audio_ && !cras_client_get_system_muted(client_)) {
+      cras_client_set_system_mute(client_, 1);
+      mute_done_ = true;
+    }
+
     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 +241,11 @@ void CrasInputStream::Stop() {
   if (!callback_ || !started_)
     return;
 
+  if (mute_system_audio_ && mute_done_) {

[DaleCurtis, 2016/07/26 23:42:58]

Open is called once, but Start()/Stop() may be called multiple times. Is this
the right place for this?

[qiangchen, 2016/07/27 17:23:48]

Done.

+    cras_client_set_system_mute(client_, 0);
+    mute_done_ = false;
+  }
+
   StopAgc();
 
   // Removing the stream from the client stops audio.