MuteSource Audio During Full Screen Cast

chrome/browser/media/desktop_capture_access_handler.cc

 // Copyright 2015 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 "chrome/browser/media/desktop_capture_access_handler.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 122 matching lines @@
   }
   return base::string16();
 }
 // Helper to get list of media stream devices for desktop capture in |devices|.
 // Registers to display notification if |display_notification| is true.
 // Returns an instance of MediaStreamUI to be passed to content layer.
 std::unique_ptr<content::MediaStreamUI> GetDevicesForDesktopCapture(
     content::MediaStreamDevices* devices,
     content::DesktopMediaID media_id,
     bool capture_audio,
+    bool mute_system_audio,

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

Can this method be called with media_id set to kLoopbackWithMuteDeviceId,
instead of adding this extra boolean to this already-huge argument list?

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

This function is shared between HandleRequest and ProcessScreenCaptureRequest.
The former is for chooseDesktopMedia and the latter for getUserMedia({screen}),
and thus we need to cater different use.

     bool display_notification,
     const base::string16& application_title,
     const base::string16& registered_extension_name) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   std::unique_ptr<content::MediaStreamUI> ui;
 
   // Add selected desktop source to the list.
   devices->push_back(content::MediaStreamDevice(
       content::MEDIA_DESKTOP_VIDEO_CAPTURE, media_id.ToString(), "Screen"));
   if (capture_audio) {
     if (media_id.type == content::DesktopMediaID::TYPE_WEB_CONTENTS) {
       devices->push_back(
           content::MediaStreamDevice(content::MEDIA_DESKTOP_AUDIO_CAPTURE,
                                      media_id.ToString(), "Tab audio"));
+    } else if (mute_system_audio) {
+      // Use the special loopback device ID for system audio capture.
+      devices->push_back(content::MediaStreamDevice(
+          content::MEDIA_DESKTOP_AUDIO_CAPTURE,
+          media::AudioDeviceDescription::kLoopbackWithMuteDeviceId,
+          "System Audio"));
     } else {
       // Use the special loopback device ID for system audio capture.
       devices->push_back(content::MediaStreamDevice(
           content::MEDIA_DESKTOP_AUDIO_CAPTURE,
           media::AudioDeviceDescription::kLoopbackInputDeviceId,
           "System Audio"));
     }
   }
 
   // If required, register to display the notification for stream capture.
@@ skipping 135 matching lines @@
 #endif  // !defined(OS_CHROMEOS)
 
       bool capture_audio =
           (request.audio_type == content::MEDIA_DESKTOP_AUDIO_CAPTURE &&
            loopback_audio_supported);
 
       // Unless we're being invoked from a component extension, register to
       // display the notification for stream capture.
       bool display_notification = !component_extension;
 
-      ui = GetDevicesForDesktopCapture(&devices, screen_id, capture_audio,
+      ui = GetDevicesForDesktopCapture(&devices, screen_id, capture_audio, true,
                                        display_notification, application_title,
                                        application_title);
       DCHECK(!devices.empty());
     }
 
     // The only case when devices can be empty is if the user has denied
     // permission.
     result = devices.empty() ? content::MEDIA_DEVICE_PERMISSION_DENIED
                              : content::MEDIA_DEVICE_OK;
   }
@@ skipping 88 matching lines @@
        loopback_audio_supported) ||
       media_id.type == content::DesktopMediaID::TYPE_WEB_CONTENTS;
 
   const bool check_audio_permission =
       !base::CommandLine::ForCurrentProcess()->HasSwitch(
           extensions::switches::kDisableDesktopCaptureAudio);
   const bool capture_audio =
       (check_audio_permission ? audio_permitted : true) && audio_requested &&
       audio_supported;
 
-  ui = GetDevicesForDesktopCapture(&devices, media_id, capture_audio, true,
+  ui = GetDevicesForDesktopCapture(&devices, media_id, capture_audio, false,
+                                   true,
                                    GetApplicationTitle(web_contents, extension),
                                    base::UTF8ToUTF16(original_extension_name));
   UpdateExtensionTrusted(request, extension);
   callback.Run(devices, content::MEDIA_DEVICE_OK, std::move(ui));
 }