MuteSource Audio During Full Screen Cast

media/audio/cras/cras_input.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/audio/cras/cras_input.h"
 
 #include <math.h>
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/time/time.h"
 #include "media/audio/audio_device_description.h"
 #include "media/audio/audio_manager.h"
 #include "media/audio/cras/audio_manager_cras.h"
 
 namespace media {
 
 CrasInputStream::CrasInputStream(const AudioParameters& params,
                                  AudioManagerCras* manager,
                                  const std::string& device_id)
     : audio_manager_(manager),
       bytes_per_frame_(0),
       callback_(NULL),
       client_(NULL),
       params_(params),
       started_(false),
       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_);
 }
 
 CrasInputStream::~CrasInputStream() {
   DCHECK(!client_);
 }
 
 bool CrasInputStream::Open() {
   if (client_) {
@@ skipping 44 matching lines @@
 
   if (is_loopback_) {
     if (cras_client_connected_wait(client_) < 0) {
       DLOG(WARNING) << "Couldn't synchronize data.";
       // TODO(chinyue): Add a DestroyClientOnError method to de-duplicate the
       // cleanup code.
       cras_client_destroy(client_);
       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) {
       DLOG(WARNING) << "Couldn't find CRAS loopback device.";
       cras_client_destroy(client_);
       client_ = NULL;
       return false;
     }
   }
 
@@ skipping 118 matching lines @@
   started_ = true;
 }
 
 void CrasInputStream::Stop() {
   if (!client_)
     return;
 
   if (!callback_ || !started_)
     return;
 
+  if (mute_system_audio_) {
+    cras_client_set_system_mute(client_, 0);
+  }
+
   StopAgc();
 
   // Removing the stream from the client stops audio.
   cras_client_rm_stream(client_, stream_id_);
 
   started_ = false;
   callback_ = NULL;
 }
 
 // Static callback asking for samples.  Run on high priority thread.
@@ skipping 91 matching lines @@
 
 double CrasInputStream::GetVolumeRatioFromDecibels(double dB) const {
   return pow(10, dB / 20.0);
 }
 
 double CrasInputStream::GetDecibelsFromVolumeRatio(double volume_ratio) const {
   return 20 * log10(volume_ratio);
 }
 
 }  // namespace media