GStreamer: improve pipeline modification code

* avoid setPipeline in `QGstreamerCamera` and `QGstreamerAudioOutput`,
  since we now can obtain the pipeline from the output/camera elements
* introduce static `modifyPipelineWhileNotRunning` helper to
  `QGstPipeline`
* Ensure that `setAudioDevice` only modifies the pipeline while the
  pipeline is not running

Task-number: QTBUG-119535
Pick-to: 6.5
Change-Id: Iad4cc887d8d2acddea4cf0c515545588558b652f
Reviewed-by: Lars Knoll <lars@knoll.priv.no>
(cherry picked from commit e0ff2ec5c8f8517f5cb55f3c2596abe262350ffc)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit 5b3803a70eed01d059a0a161da9925684983c4b2)

9 files changed, 40 insertions, 60 deletions

diff --git a/src/plugins/multimedia/gstreamer/common/qgstpipeline_p.h b/src/plugins/multimedia/gstreamer/common/qgstpipeline_p.h
index c13196d12..d04bd84d8 100644
--- a/src/plugins/multimedia/gstreamer/common/qgstpipeline_p.h
+++ b/src/plugins/multimedia/gstreamer/common/qgstpipeline_p.h
@@ -81,6 +81,15 @@ public:
         endConfig();
     }
 
+    template <typename Functor>
+    static void modifyPipelineWhileNotRunning(QGstPipeline &&pipeline, Functor &&fn)
+    {
+        if (pipeline)
+            pipeline.modifyPipelineWhileNotRunning(fn);
+        else
+            fn();
+    }
+
     void flush();
 
     bool seek(qint64 pos, double rate);
diff --git a/src/plugins/multimedia/gstreamer/common/qgstreameraudioinput.cpp b/src/plugins/multimedia/gstreamer/common/qgstreameraudioinput.cpp
index d6b40ea21..0381b921e 100644
--- a/src/plugins/multimedia/gstreamer/common/qgstreameraudioinput.cpp
+++ b/src/plugins/multimedia/gstreamer/common/qgstreameraudioinput.cpp
@@ -89,13 +89,14 @@ void QGstreamerAudioInput::setAudioDevice(const QAudioDevice &device)
         newSrc = QGstElement::createFromFactory("autoaudiosrc", "audiosrc");
     }
 
-    // FIXME: most probably source can be disconnected outside of idle probe
-    audioSrc.staticPad("src").doInIdleProbe([&]() { qUnlinkGstElements(audioSrc, audioVolume); });
-    gstAudioInput.stopAndRemoveElements(audioSrc);
-    audioSrc = newSrc;
-    gstAudioInput.add(audioSrc);
-    qLinkGstElements(audioSrc, audioVolume);
-    audioSrc.syncStateWithParent();
+    QGstPipeline::modifyPipelineWhileNotRunning(gstAudioInput.getPipeline(), [&] {
+        qUnlinkGstElements(audioSrc, audioVolume);
+        gstAudioInput.stopAndRemoveElements(audioSrc);
+        audioSrc = std::move(newSrc);
+        gstAudioInput.add(audioSrc);
+        qLinkGstElements(audioSrc, audioVolume);
+        audioSrc.syncStateWithParent();
+    });
 }
 
 QAudioDevice QGstreamerAudioInput::audioInput() const
diff --git a/src/plugins/multimedia/gstreamer/common/qgstreameraudiooutput.cpp b/src/plugins/multimedia/gstreamer/common/qgstreameraudiooutput.cpp
index efb1789e8..f45c371e9 100644
--- a/src/plugins/multimedia/gstreamer/common/qgstreameraudiooutput.cpp
+++ b/src/plugins/multimedia/gstreamer/common/qgstreameraudiooutput.cpp
@@ -68,11 +68,6 @@ void QGstreamerAudioOutput::setMuted(bool muted)
     audioVolume.set("mute", muted);
 }
 
-void QGstreamerAudioOutput::setPipeline(const QGstPipeline &pipeline)
-{
-    gstPipeline = pipeline;
-}
-
 void QGstreamerAudioOutput::setAudioDevice(const QAudioDevice &info)
 {
     if (info == m_audioOutput)
@@ -101,16 +96,14 @@ void QGstreamerAudioOutput::setAudioDevice(const QAudioDevice &info)
         newSink = QGstElement::createFromFactory("autoaudiosink", "audiosink");
     }
 
-    audioVolume.staticPad("src").doInIdleProbe([&]() {
+    QGstPipeline::modifyPipelineWhileNotRunning(gstAudioOutput.getPipeline(), [&] {
         qUnlinkGstElements(audioVolume, audioSink);
-        gstAudioOutput.remove(audioSink);
-        gstAudioOutput.add(newSink);
-        newSink.syncStateWithParent();
-        qLinkGstElements(audioVolume, newSink);
+        gstAudioOutput.stopAndRemoveElements(audioSink);
+        audioSink = std::move(newSink);
+        gstAudioOutput.add(audioSink);
+        audioSink.syncStateWithParent();
+        qLinkGstElements(audioVolume, audioSink);
     });
-
-    audioSink.setStateSync(GST_STATE_NULL);
-    audioSink = newSink;
 }
 
 QT_END_NAMESPACE
diff --git a/src/plugins/multimedia/gstreamer/common/qgstreameraudiooutput_p.h b/src/plugins/multimedia/gstreamer/common/qgstreameraudiooutput_p.h
index a8680b634..4b528d9ee 100644
--- a/src/plugins/multimedia/gstreamer/common/qgstreameraudiooutput_p.h
+++ b/src/plugins/multimedia/gstreamer/common/qgstreameraudiooutput_p.h
@@ -38,8 +38,6 @@ public:
     void setVolume(float) override;
     void setMuted(bool) override;
 
-    void setPipeline(const QGstPipeline &pipeline);
-
     QGstElement gstElement() const { return gstAudioOutput; }
 
 private:
diff --git a/src/plugins/multimedia/gstreamer/common/qgstreamermediaplayer.cpp b/src/plugins/multimedia/gstreamer/common/qgstreamermediaplayer.cpp
index e318c14eb..a4e2036e7 100644
--- a/src/plugins/multimedia/gstreamer/common/qgstreamermediaplayer.cpp
+++ b/src/plugins/multimedia/gstreamer/common/qgstreamermediaplayer.cpp
@@ -771,15 +771,12 @@ void QGstreamerMediaPlayer::setAudioOutput(QPlatformAudioOutput *output)
     auto &ts = trackSelector(AudioStream);
 
     playerPipeline.modifyPipelineWhileNotRunning([&] {
-        if (gstAudioOutput) {
+        if (gstAudioOutput)
             removeOutput(ts);
-            gstAudioOutput->setPipeline({});
-        }
+
         gstAudioOutput = static_cast<QGstreamerAudioOutput *>(output);
-        if (gstAudioOutput) {
-            gstAudioOutput->setPipeline(playerPipeline);
+        if (gstAudioOutput)
             connectOutput(ts);
-        }
     });
 }
 
diff --git a/src/plugins/multimedia/gstreamer/common/qgstreamervideosink.cpp b/src/plugins/multimedia/gstreamer/common/qgstreamervideosink.cpp
index 21b64f997..c70428485 100644
--- a/src/plugins/multimedia/gstreamer/common/qgstreamervideosink.cpp
+++ b/src/plugins/multimedia/gstreamer/common/qgstreamervideosink.cpp
@@ -133,7 +133,7 @@ QGstElement QGstreamerVideoSink::gstSink()
 
 void QGstreamerVideoSink::setPipeline(QGstPipeline pipeline)
 {
-    gstPipeline = pipeline;
+    gstPipeline = std::move(pipeline);
 }
 
 bool QGstreamerVideoSink::inStoppedState() const
diff --git a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamercamera.cpp b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamercamera.cpp
index c14a34c22..8d3cd6baf 100644
--- a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamercamera.cpp
+++ b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamercamera.cpp
@@ -104,25 +104,20 @@ void QGstreamerCamera::setCamera(const QCameraDevice &camera)
     auto gstNewDecode = QGstElement::createFromFactory(
             f.pixelFormat() == QVideoFrameFormat::Format_Jpeg ? "jpegdec" : "identity");
 
-    auto updateCameraBin = [&] {
+    QGstPipeline::modifyPipelineWhileNotRunning(gstCamera.getPipeline(), [&] {
         qUnlinkGstElements(gstCamera, gstCapsFilter, gstDecode, gstVideoConvert);
         gstCameraBin.stopAndRemoveElements(gstCamera, gstDecode);
 
         gstCapsFilter.set("caps", caps);
 
-        gstCameraBin.add(gstNewCamera, gstNewDecode);
-        qLinkGstElements(gstNewCamera, gstCapsFilter, gstNewDecode, gstVideoConvert);
+        gstCamera = std::move(gstNewCamera);
+        gstDecode = std::move(gstNewDecode);
 
-        gstCameraBin.syncChildrenState();
-    };
-
-    if (gstPipeline)
-        gstPipeline.modifyPipelineWhileNotRunning(updateCameraBin);
-    else
-        updateCameraBin();
+        gstCameraBin.add(gstCamera, gstDecode);
+        qLinkGstElements(gstCamera, gstCapsFilter, gstDecode, gstVideoConvert);
 
-    gstCamera = gstNewCamera;
-    gstDecode = gstNewDecode;
+        gstCameraBin.syncChildrenState();
+    });
 
     updateCameraProperties();
 }
@@ -141,7 +136,7 @@ bool QGstreamerCamera::setCameraFormat(const QCameraFormat &format)
     auto newGstDecode = QGstElement::createFromFactory(
             f.pixelFormat() == QVideoFrameFormat::Format_Jpeg ? "jpegdec" : "identity");
 
-    auto updateCameraBin = [&] {
+    QGstPipeline::modifyPipelineWhileNotRunning(gstCamera.getPipeline(), [&] {
         newGstDecode.syncStateWithParent();
 
         qUnlinkGstElements(gstCamera, gstCapsFilter, gstDecode, gstVideoConvert);
@@ -149,26 +144,16 @@ bool QGstreamerCamera::setCameraFormat(const QCameraFormat &format)
 
         gstCapsFilter.set("caps", caps);
 
-        gstCameraBin.add(newGstDecode);
-        qLinkGstElements(gstCamera, gstCapsFilter, newGstDecode, gstVideoConvert);
-        gstCameraBin.syncChildrenState();
-    };
-
-    if (gstPipeline)
-        gstPipeline.modifyPipelineWhileNotRunning(updateCameraBin);
-    else
-        updateCameraBin();
+        gstDecode = std::move(newGstDecode);
 
-    gstDecode = newGstDecode;
+        gstCameraBin.add(gstDecode);
+        qLinkGstElements(gstCamera, gstCapsFilter, gstDecode, gstVideoConvert);
+        gstCameraBin.syncChildrenState();
+    });
 
     return true;
 }
 
-void QGstreamerCamera::setPipeline(QGstPipeline const &pipeline)
-{
-    gstPipeline = pipeline;
-}
-
 void QGstreamerCamera::updateCameraProperties()
 {
 #if QT_CONFIG(linux_v4l)
diff --git a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamercamera_p.h b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamercamera_p.h
index a85180595..74f12f918 100644
--- a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamercamera_p.h
+++ b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamercamera_p.h
@@ -38,7 +38,6 @@ public:
     void setCamera(const QCameraDevice &camera) override;
     bool setCameraFormat(const QCameraFormat &format) override;
 
-    void setPipeline(const QGstPipeline &);
     QGstElement gstElement() const { return gstCameraBin; }
 #if QT_CONFIG(gstreamer_photography)
     GstPhotography *photography() const;
diff --git a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture.cpp b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture.cpp
index e28712aea..40ad0bc74 100644
--- a/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture.cpp
+++ b/src/plugins/multimedia/gstreamer/mediacapture/qgstreamermediacapture.cpp
@@ -92,13 +92,11 @@ void QGstreamerMediaCapture::setCamera(QPlatformCamera *platformCamera)
         QObject::disconnect(gstCameraActiveConnection);
         if (gstVideoTee)
             setCameraActive(false);
-        gstCamera->setPipeline({});
     }
 
     gstCamera = camera;
 
     if (gstCamera) {
-        gstCamera->setPipeline(gstPipeline);
         gstCameraActiveConnection = QObject::connect(camera, &QGstreamerCamera::activeChanged, this,
                                                      &QGstreamerMediaCapture::setCameraActive);
         if (gstCamera->isActive())