Added AVFoundation Glue and Device Monitoring for Mac.

content/browser/device_monitor_mac.mm

 // 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 "content/browser/device_monitor_mac.h"
 
 #import <QTKit/QTKit.h>
 
 #include "base/logging.h"
-
-namespace content {
-
-class DeviceMonitorMac::QTMonitorImpl {
- public:
-  explicit QTMonitorImpl(DeviceMonitorMac* monitor);
-  virtual ~QTMonitorImpl() {}
-
-  void Start();
-  void Stop();
+#import "media/video/capture/mac/avfoundation_glue.h"
+
+namespace {
+
+// This class is used to keep track of system devices names and their types.
+class DeviceInfo {
+ public:
+  enum DeviceType {
+    kAudio,
+    kVideo,
+    kMuxed
+  };
+
+  DeviceInfo(std::string unique_id, DeviceType type)
+      : unique_id_(unique_id), type_(type) {}
+
+  // Operator== is needed here to use this class in a std::vector.
+  bool operator==(const DeviceInfo& device) const {
+    return unique_id_ == device.unique_id_;
+  }
+
+  const std::string& unique_id() const { return unique_id_; }
+  DeviceType type() const { return type_; }
 
  private:
-  void OnDeviceChanged();
-
-  DeviceMonitorMac* monitor_;
-  int number_audio_devices_;
-  int number_video_devices_;
+  std::string unique_id_;
+  DeviceType type_;
+  // Allow generated copy constructor and assignment.
+};
+
+// Base class used by DeviceMonitorMac to interact with either a QTKit or an
+// AVFoundation implementation of events and notifications. This class should
+// never be instantiated on its own.
+class MacMonitor {
+ public:
+  explicit MacMonitor(content::DeviceMonitorMac* monitor)
+      : monitor_(monitor),
+        cached_devices_(),
+        device_arrival_(nil),
+        device_removal_(nil) {
+    DCHECK(monitor);
+  }
+  virtual ~MacMonitor() {}
+
+  virtual void OnDeviceChanged() = 0;

[Robert Sesek, 2013/10/16 23:58:07]

nit: blank line after

[mcasas, 2013/10/17 08:16:36]

Done.

+  // Method called by the default notification center when a device is removed
+  // or added to the system. It will compare the |cached_devices_| with the
+  // current situation, update it, and, if there's an update, signal to
+  // |monitor_| with the appropriate device type.
+  void ConsolidateDevicesListAndNotify(
+      std::vector<DeviceInfo> snapshot_devices);

[Robert Sesek, 2013/10/16 23:58:07]

|snapshot_devices| should also be a const-ref.

[mcasas, 2013/10/17 08:16:36]

Done.

+
+ protected:
+  content::DeviceMonitorMac* monitor_;
+  std::vector<DeviceInfo> cached_devices_;
   id device_arrival_;

[Robert Sesek, 2013/10/16 23:58:07]

It's not clear from the names what these are. Comment to the effect of: "//
Handles to NSNotificationCenter block observers."

[mcasas, 2013/10/17 08:16:36]

Done.

   id device_removal_;
-
-  DISALLOW_COPY_AND_ASSIGN(QTMonitorImpl);
-};
-
-DeviceMonitorMac::QTMonitorImpl::QTMonitorImpl(DeviceMonitorMac* monitor)
-    : monitor_(monitor),
-      number_audio_devices_(0),
-      number_video_devices_(0),
-      device_arrival_(nil),
-      device_removal_(nil) {
-  DCHECK(monitor);
-}
-
-void DeviceMonitorMac::QTMonitorImpl::Start() {
+  DISALLOW_COPY_AND_ASSIGN(MacMonitor);
+};
+
+void MacMonitor::ConsolidateDevicesListAndNotify(
+    std::vector<DeviceInfo> snapshot_devices) {
+  bool video_device_added = false;
+  bool audio_device_added = false;
+  bool video_device_removed = false;
+  bool audio_device_removed = false;
+
+  // Compare the current system devices snapshot with the ones cached to detect
+  // additions, present in the former but not in the latter. If we find a device
+  // in snapshot_devices entry also present in cached_devices, we remove it from
+  // the latter vector.
+  std::vector<DeviceInfo>::iterator it;
+  for (it = snapshot_devices.begin(); it != snapshot_devices.end(); ++it) {
+    std::vector<DeviceInfo>::iterator cached_devices_iterator =
+        std::find(cached_devices_.begin(), cached_devices_.end(), *it);
+    if (cached_devices_iterator == cached_devices_.end()) {
+      video_device_added |= ((it->type() == DeviceInfo::kVideo) ||
+                             (it->type() == DeviceInfo::kMuxed));
+      audio_device_added |= ((it->type() == DeviceInfo::kAudio) ||
+                             (it->type() == DeviceInfo::kMuxed));
+      DVLOG(1) << "Device has been added, id: " << it->unique_id();
+    } else {
+      cached_devices_.erase(cached_devices_iterator);
+    }
+  }
+  // All the remaining entries in cached_devices are removed devices.
+  for (it = cached_devices_.begin(); it != cached_devices_.end(); ++it) {
+    video_device_removed |= ((it->type() == DeviceInfo::kVideo) ||
+                             (it->type() == DeviceInfo::kMuxed));
+    audio_device_removed |= ((it->type() == DeviceInfo::kAudio) ||
+                             (it->type() == DeviceInfo::kMuxed));
+    DVLOG(1) << "Device has been removed, id: " << it->unique_id();
+  }
+  // Update the cached devices with the current system snapshot.
+  cached_devices_.swap(snapshot_devices);
+
+  if (video_device_added || video_device_removed)
+    monitor_->NotifyDeviceChanged(base::SystemMonitor::DEVTYPE_VIDEO_CAPTURE);
+  if (audio_device_added || video_device_removed)
+    monitor_->NotifyDeviceChanged(base::SystemMonitor::DEVTYPE_AUDIO_CAPTURE);
+}
+
+class QTKitMonitorImpl : public MacMonitor {
+ public:
+  explicit QTKitMonitorImpl(content::DeviceMonitorMac* monitor);
+  virtual ~QTKitMonitorImpl();
+
+  virtual void OnDeviceChanged() OVERRIDE;
+};
+
+QTKitMonitorImpl::QTKitMonitorImpl(content::DeviceMonitorMac* monitor)
+    : MacMonitor(monitor) {
   NSNotificationCenter* nc = [NSNotificationCenter defaultCenter];
   device_arrival_ =
-    [nc addObserverForName:QTCaptureDeviceWasConnectedNotification
-                    object:nil
-                     queue:nil
-                usingBlock:^(NSNotification* notification) {
-                    OnDeviceChanged();}];
+      [nc addObserverForName:QTCaptureDeviceWasConnectedNotification
+                      object:nil
+                       queue:nil

[Robert Sesek, 2013/10/16 23:58:07]

Why nil queue here but mainQueue below? What are the threading restrictions on
these classes? SystemMonitor does not document the threading contract for
ProcessDevicesChanged().

[mcasas, 2013/10/17 08:16:36]

Remainings of an experiment with mmentovai@. The mainqueue is used by default,
so both codes are equivalent queue-wise. Put both queue usages to nil.

SystemMonitor indeed does not explicit how it behaves with respect to threading.
But finally it ends calling all observers via ObserverListThreadSafe pointers.

[Robert Sesek, 2013/10/18 18:18:15]

That's not accurate:

"If you pass nil, the block is run synchronously on the posting thread."

https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundat...:
Yup.

+                  usingBlock:^(NSNotification* notification) {
+                      OnDeviceChanged();
+                  }];
 
   device_removal_ =
       [nc addObserverForName:QTCaptureDeviceWasDisconnectedNotification
                       object:nil
                        queue:nil
                   usingBlock:^(NSNotification* notification) {
-                      OnDeviceChanged();}];
-}
-
-void DeviceMonitorMac::QTMonitorImpl::Stop() {
-  if (!monitor_)
-    return;
-
+                      OnDeviceChanged();
+                  }];
+}
+
+QTKitMonitorImpl::~QTKitMonitorImpl() {
   NSNotificationCenter* nc = [NSNotificationCenter defaultCenter];
   [nc removeObserver:device_arrival_];
   [nc removeObserver:device_removal_];
 }
 
-void DeviceMonitorMac::QTMonitorImpl::OnDeviceChanged() {
+void QTKitMonitorImpl::OnDeviceChanged() {
+  std::vector<DeviceInfo> snapshot_devices;
+  DeviceInfo::DeviceType device_info;
+
   NSArray* devices = [QTCaptureDevice inputDevices];
-  int number_video_devices = 0;
-  int number_audio_devices = 0;
   for (QTCaptureDevice* device in devices) {
-    if ([device hasMediaType:QTMediaTypeVideo] ||
-        [device hasMediaType:QTMediaTypeMuxed])
-      ++number_video_devices;
-
-    if ([device hasMediaType:QTMediaTypeSound] ||
-        [device hasMediaType:QTMediaTypeMuxed])
-      ++number_audio_devices;
-  }
-
-  if (number_video_devices_ != number_video_devices) {
-    number_video_devices_ = number_video_devices;
-    monitor_->NotifyDeviceChanged(base::SystemMonitor::DEVTYPE_VIDEO_CAPTURE);
-  }
-
-  if (number_audio_devices_ != number_audio_devices) {
-    number_audio_devices_ = number_audio_devices;
-    monitor_->NotifyDeviceChanged(base::SystemMonitor::DEVTYPE_AUDIO_CAPTURE);
-  }
-}
+    if ([device hasMediaType:QTMediaTypeVideo])
+      device_info = DeviceInfo::kVideo;
+    else if ([device hasMediaType:QTMediaTypeMuxed])
+      device_info = DeviceInfo::kMuxed;
+    else if ([device hasMediaType:QTMediaTypeSound])
+      device_info = DeviceInfo::kAudio;
+
+    snapshot_devices.push_back(
+        DeviceInfo([[device uniqueID] UTF8String], device_info));
+  }
+
+  ConsolidateDevicesListAndNotify(snapshot_devices);
+}
+
+class AVFoundationMonitorImpl : public MacMonitor {
+ public:
+  explicit AVFoundationMonitorImpl(content::DeviceMonitorMac* monitor);
+  virtual ~AVFoundationMonitorImpl();
+
+  virtual void OnDeviceChanged() OVERRIDE;
+};
+
+AVFoundationMonitorImpl::AVFoundationMonitorImpl(
+    content::DeviceMonitorMac* monitor)
+    : MacMonitor(monitor) {
+  NSNotificationCenter* nc = [NSNotificationCenter defaultCenter];
+  NSOperationQueue* main_queue = [NSOperationQueue mainQueue];
+
+  device_arrival_ =
+      [nc addObserverForName:AVFoundationGlue::
+      AvCaptureDeviceWasConnectedNotification()
+                      object:nil
+                       queue:main_queue
+                  usingBlock:^(NSNotification* notification) {
+                      OnDeviceChanged();
+                  }];
+  DCHECK(device_arrival_);
+  device_removal_ =
+      [nc addObserverForName:AVFoundationGlue::
+      AvCaptureDeviceWasDisconnectedNotification()
+                      object:nil
+                       queue:main_queue
+                  usingBlock:^(NSNotification* notification) {
+                      OnDeviceChanged();
+                  }];
+  DCHECK(device_removal_);
+}
+
+AVFoundationMonitorImpl::~AVFoundationMonitorImpl() {
+  NSNotificationCenter* nc = [NSNotificationCenter defaultCenter];
+  [nc removeObserver:device_arrival_];
+  [nc removeObserver:device_removal_];
+}
+
+void AVFoundationMonitorImpl::OnDeviceChanged() {
+  std::vector<DeviceInfo> snapshot_devices;
+  DeviceInfo::DeviceType device_info;
+
+  NSArray* devices = [AVCaptureDeviceGlue devices];
+  for (CrAVCaptureDevice* device in devices) {
+    if ([AVCaptureDeviceGlue hasMediaType:AVFoundationGlue::AvMediaTypeVideo()
+                         forCaptureDevice:device]) {
+      device_info = DeviceInfo::kVideo;
+    } else if ([AVCaptureDeviceGlue
+                   hasMediaType:AVFoundationGlue::AvMediaTypeMuxed()
+               forCaptureDevice:device]) {
+      device_info = DeviceInfo::kMuxed;
+    } else if ([AVCaptureDeviceGlue
+                   hasMediaType:AVFoundationGlue::AvMediaTypeAudio()
+               forCaptureDevice:device]) {
+      device_info = DeviceInfo::kAudio;
+    }
+    snapshot_devices.push_back(DeviceInfo(
+        [[AVCaptureDeviceGlue uniqueID:device] UTF8String], device_info));
+  }
+
+  ConsolidateDevicesListAndNotify(snapshot_devices);
+}
+
+}  // namespace
+
+namespace content {
 
 DeviceMonitorMac::DeviceMonitorMac() {
-  qt_monitor_.reset(new QTMonitorImpl(this));
-  qt_monitor_->Start();
-}
-
-DeviceMonitorMac::~DeviceMonitorMac() {
-  qt_monitor_->Stop();
-}
+  if (AVFoundationGlue::IsAVFoundationSupported()) {
+    DVLOG(1) << "Monitoring via AVFoundation";
+    device_monitor_impl_.reset(new AVFoundationMonitorImpl(this));
+    // Force the device enumeration so we enumerate correctly devices already in
+    // the system and at the same time use the AVCaptureDeviceGlue so it in
+    // turn forces the AVCaptureDeviceGlue alloc-init.
+    device_monitor_impl_->OnDeviceChanged();

[Robert Sesek, 2013/10/16 23:58:07]

Why isn't this done for the QTKit impl?

[mcasas, 2013/10/17 08:16:36]

It should be done indeed, to create the |cached_devices_|.

+  } else {
+    DVLOG(1) << "Monitoring via QTKit";
+    device_monitor_impl_.reset(new QTKitMonitorImpl(this));
+  }
+}
+
+DeviceMonitorMac::~DeviceMonitorMac() {}
 
 void DeviceMonitorMac::NotifyDeviceChanged(
     base::SystemMonitor::DeviceType type) {
   // TODO(xians): Remove the global variable for SystemMonitor.
   base::SystemMonitor::Get()->ProcessDevicesChanged(type);
 }
 
 }  // namespace content