DirectShow: Allow QMediaPlayer in secondary thread

Since using of any COM objects must be only after CoInitialize(),
otherwise CoCreateInstance() returns nothing which causes a crash.

If QMediaPlayer is moved to another thread, loading of any content will
also cause a crash because of COM is not initialized.

Proposing to use thread_local ref counter to keep each thread
initialized and avoid double initialization.

Fixes: QTBUG-77163
Change-Id: I81c67d6407b853c824edd3b42454fddf792fd90c
Reviewed-by: Christian Strømme <christian.stromme@qt.io>

4 files changed, 29 insertions, 22 deletions

diff --git a/src/plugins/directshow/common/directshowutils.cpp b/src/plugins/directshow/common/directshowutils.cpp
index 48d5dbd8d..13b51deb5 100644
--- a/src/plugins/directshow/common/directshowutils.cpp
+++ b/src/plugins/directshow/common/directshowutils.cpp
@@ -309,4 +309,17 @@ bool DirectShowUtils::connectFilters(IGraphBuilder *graph,
     return false;
 }
 
+thread_local static int g_refCount = 0;
+void DirectShowUtils::CoInitializeIfNeeded()
+{
+    if (++g_refCount == 1)
+        ::CoInitialize(nullptr);
+}
+
+void DirectShowUtils::CoUninitializeIfNeeded()
+{
+    if (--g_refCount == 0)
+        ::CoUninitialize();
+}
+
 QT_END_NAMESPACE
diff --git a/src/plugins/directshow/common/directshowutils.h b/src/plugins/directshow/common/directshowutils.h
index 09c81c257..5f2cfaa23 100644
--- a/src/plugins/directshow/common/directshowutils.h
+++ b/src/plugins/directshow/common/directshowutils.h
@@ -80,6 +80,10 @@ bool connectFilters(IGraphBuilder *graph,
                     IBaseFilter *downstreamFilter,
                     bool autoConnect = false,
                     HRESULT *hrOut = nullptr);
+
+void CoInitializeIfNeeded();
+void CoUninitializeIfNeeded();
+
 }
 
 QT_END_NAMESPACE
diff --git a/src/plugins/directshow/dsserviceplugin.cpp b/src/plugins/directshow/dsserviceplugin.cpp
index f92e37c00..cc25e35b7 100644
--- a/src/plugins/directshow/dsserviceplugin.cpp
+++ b/src/plugins/directshow/dsserviceplugin.cpp
@@ -54,6 +54,7 @@
 #include "directshowplayerservice.h"
 
 #include <qmediaserviceproviderplugin.h>
+#include "directshowutils.h"
 
 extern const CLSID CLSID_VideoInputDeviceCategory;
 
@@ -74,28 +75,15 @@ extern const CLSID CLSID_VideoInputDeviceCategory;
 QT_BEGIN_NAMESPACE
 Q_LOGGING_CATEGORY(qtDirectShowPlugin, "qt.multimedia.plugins.directshow")
 
-static int g_refCount = 0;
-void addRefCount()
-{
-    if (++g_refCount == 1)
-        CoInitialize(nullptr);
-}
-
-void releaseRefCount()
-{
-    if (--g_refCount == 0)
-        CoUninitialize();
-}
-
 QMediaService* DSServicePlugin::create(QString const& key)
 {
     if (key == QLatin1String(Q_MEDIASERVICE_CAMERA)) {
-        addRefCount();
+        DirectShowUtils::CoInitializeIfNeeded();
         return new DSCameraService;
     }
 
     if (key == QLatin1String(Q_MEDIASERVICE_MEDIAPLAYER)) {
-        addRefCount();
+        DirectShowUtils::CoInitializeIfNeeded();
         return new DirectShowPlayerService;
     }
 
@@ -105,7 +93,7 @@ QMediaService* DSServicePlugin::create(QString const& key)
 void DSServicePlugin::release(QMediaService *service)
 {
     delete service;
-    releaseRefCount();
+    DirectShowUtils::CoUninitializeIfNeeded();
 }
 
 QMediaServiceProviderHint::Features DSServicePlugin::supportedFeatures(
@@ -119,9 +107,9 @@ QMediaServiceProviderHint::Features DSServicePlugin::supportedFeatures(
 QByteArray DSServicePlugin::defaultDevice(const QByteArray &service) const
 {
     if (service == Q_MEDIASERVICE_CAMERA) {
-        addRefCount();
+        DirectShowUtils::CoInitializeIfNeeded();
         const QList<DSVideoDeviceInfo> &devs = DSVideoDeviceControl::availableDevices();
-        releaseRefCount();
+        DirectShowUtils::CoUninitializeIfNeeded();
         if (!devs.isEmpty())
             return devs.first().first;
     }
@@ -133,9 +121,9 @@ QList<QByteArray> DSServicePlugin::devices(const QByteArray &service) const
     QList<QByteArray> result;
 
     if (service == Q_MEDIASERVICE_CAMERA) {
-        addRefCount();
+        DirectShowUtils::CoInitializeIfNeeded();
         const QList<DSVideoDeviceInfo> &devs = DSVideoDeviceControl::availableDevices();
-        releaseRefCount();
+        DirectShowUtils::CoUninitializeIfNeeded();
         for (const DSVideoDeviceInfo &info : devs)
             result.append(info.first);
     }
@@ -146,9 +134,9 @@ QList<QByteArray> DSServicePlugin::devices(const QByteArray &service) const
 QString DSServicePlugin::deviceDescription(const QByteArray &service, const QByteArray &device)
 {
     if (service == Q_MEDIASERVICE_CAMERA) {
-        addRefCount();
+        DirectShowUtils::CoInitializeIfNeeded();
         const QList<DSVideoDeviceInfo> &devs = DSVideoDeviceControl::availableDevices();
-        releaseRefCount();
+        DirectShowUtils::CoUninitializeIfNeeded();
         for (const DSVideoDeviceInfo &info : devs) {
             if (info.first == device)
                 return info.second;
diff --git a/src/plugins/directshow/player/directshowplayerservice.cpp b/src/plugins/directshow/player/directshowplayerservice.cpp
index def18be74..f5899cb6a 100644
--- a/src/plugins/directshow/player/directshowplayerservice.cpp
+++ b/src/plugins/directshow/player/directshowplayerservice.cpp
@@ -327,6 +327,7 @@ void DirectShowPlayerService::load(const QMediaContent &media, QIODevice *stream
             0x36b73882, 0xc2c8, 0x11cf, {0x8b, 0x46, 0x00, 0x80, 0x5f, 0x6c, 0xef, 0x60} };
         m_graphStatus = Loading;
 
+        DirectShowUtils::CoInitializeIfNeeded();
         m_graph = com_new<IFilterGraph2>(CLSID_FilterGraph, iid_IFilterGraph2);
         m_graphBuilder = com_new<ICaptureGraphBuilder2>(CLSID_CaptureGraphBuilder2, IID_ICaptureGraphBuilder2);
 
@@ -664,6 +665,7 @@ void DirectShowPlayerService::releaseGraph()
         ::SetEvent(m_taskHandle);
 
         m_loop->wait(&m_mutex);
+        DirectShowUtils::CoUninitializeIfNeeded();
     }
 }