GStreamer: media capture - only capture active cameras

`Camera::setActive` did not have any effect, as the camera was always
active.
So we hook into the `QGstreamerCamera::activeChanged` signal in order to
activate the camera in QGstreamerMediaCapture.

Fixes: QTBUG-122959
Pick-to: 6.5
Change-Id: Ifce4c59f58eb074e285ee9dfc012ac8fd8637a1f
Reviewed-by: Mikko Hallamaa <mikko.hallamaa@qt.io>
Reviewed-by: Jøger Hansegård <joger.hansegard@qt.io>
Reviewed-by: Artem Dyomin <artem.dyomin@qt.io>
(cherry picked from commit b6f02dff45941494f981ae72b6981549d17b4c8b)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit a04b5d8e94f478b3643986b18792f99fe7cac420)

2 files changed, 38 insertions, 20 deletions

diff --git a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture.cpp b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture.cpp
index 86acfd07c..8eb37ac06 100644
--- a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture.cpp
+++ b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture.cpp
@@ -83,46 +83,61 @@ QPlatformCamera *QGstreamerMediaCapture::camera()
     return gstCamera;
 }
 
-void QGstreamerMediaCapture::setCamera(QPlatformCamera *camera)
+void QGstreamerMediaCapture::setCamera(QPlatformCamera *platformCamera)
 {
-    QGstreamerCamera *control = static_cast<QGstreamerCamera *>(camera);
-    if (gstCamera == control)
+    QGstreamerCamera *camera = static_cast<QGstreamerCamera *>(platformCamera);
+    if (gstCamera == camera)
         return;
 
-    gstPipeline.modifyPipelineWhileNotRunning([&] {
-        if (gstCamera) {
-            unlinkTeeFromPad(gstVideoTee, encoderVideoSink);
-            unlinkTeeFromPad(gstVideoTee, imageCaptureSink);
+    if (gstCamera) {
+        QObject::disconnect(gstCameraActiveConnection);
+        if (gstVideoTee)
+            setCameraActive(false);
+    }
 
-            auto camera = gstCamera->gstElement();
+    gstCamera = camera;
 
-            gstPipeline.stopAndRemoveElements(camera, gstVideoTee, gstVideoOutput->gstElement());
+    if (gstCamera) {
+        gstCameraActiveConnection = QObject::connect(camera, &QGstreamerCamera::activeChanged, this,
+                                                     &QGstreamerMediaCapture::setCameraActive);
+        if (gstCamera->isActive())
+            setCameraActive(true);
+    }
 
-            gstVideoTee = {};
-            gstCamera->setCaptureSession(nullptr);
-        }
+    emit cameraChanged();
+}
 
-        gstCamera = control;
-        if (gstCamera) {
-            QGstElement camera = gstCamera->gstElement();
+void QGstreamerMediaCapture::setCameraActive(bool activate)
+{
+    gstPipeline.modifyPipelineWhileNotRunning([&] {
+        if (activate) {
+            QGstElement cameraElement = gstCamera->gstElement();
             gstVideoTee = QGstElement::createFromFactory("tee", "videotee");
             gstVideoTee.set("allow-not-linked", true);
 
-            gstPipeline.add(gstVideoOutput->gstElement(), camera, gstVideoTee);
+            gstPipeline.add(gstVideoOutput->gstElement(), cameraElement, gstVideoTee);
 
             linkTeeToPad(gstVideoTee, encoderVideoSink);
             linkTeeToPad(gstVideoTee, gstVideoOutput->gstElement().staticPad("sink"));
             linkTeeToPad(gstVideoTee, imageCaptureSink);
 
-            qLinkGstElements(camera, gstVideoTee);
+            qLinkGstElements(cameraElement, gstVideoTee);
 
             gstPipeline.syncChildrenState();
+        } else {
+            unlinkTeeFromPad(gstVideoTee, encoderVideoSink);
+            unlinkTeeFromPad(gstVideoTee, imageCaptureSink);
+
+            auto camera = gstCamera->gstElement();
+
+            gstPipeline.stopAndRemoveElements(camera, gstVideoTee, gstVideoOutput->gstElement());
+
+            gstVideoTee = {};
+            gstCamera->setCaptureSession(nullptr);
         }
     });
 
     gstPipeline.dumpGraph("camera");
-
-    emit cameraChanged();
 }
 
 QPlatformImageCapture *QGstreamerMediaCapture::imageCapture()
@@ -211,7 +226,7 @@ void QGstreamerMediaCapture::linkEncoder(QGstPad audioSink, QGstPad videoSink)
 
             encoderAudioCapsFilter.src().link(audioSink);
             linkTeeToPad(gstAudioTee, encoderAudioCapsFilter.sink());
-            encoderAudioCapsFilter.syncStateWithParent();
+            encoderVideoCapsFilter.syncStateWithParent();
             encoderAudioSink = encoderAudioCapsFilter.sink();
         }
     });
diff --git a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture_p.h b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture_p.h
index f790f741f..ec7d6a3f1 100644
--- a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture_p.h
+++ b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture_p.h
@@ -64,6 +64,8 @@ public:
     QGstreamerVideoSink *gstreamerVideoSink() const;
 
 private:
+    void setCameraActive(bool activate);
+
     explicit QGstreamerMediaCapture(QGstreamerVideoOutput *videoOutput);
 
     friend QGstreamerMediaEncoder;
@@ -72,6 +74,7 @@ private:
 
     QGstreamerAudioInput *gstAudioInput = nullptr;
     QGstreamerCamera *gstCamera = nullptr;
+    QMetaObject::Connection gstCameraActiveConnection;
 
     QGstElement gstAudioTee;
     QGstElement gstVideoTee;