qml6glsrc: Reduce capture delay

In qml6glsrc, we capture the application by copying the back buffer into
our own FBO. The afterRendering() signal is too soon as from the apitrace, the
application has been rendered into a QT internal buffer, to be used as a cache
for refresh.

Use afterFrameEnd() signal instead. This works with no delay on GLES. With GL
it seems to reduce from 2 to 1 frame delay (this may be platform specific). A
different recording technique would need to be used to completely remove this
delay.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7562>

diff --git a/subprojects/gst-plugins-good/ext/qt6/qt6glwindow.cc b/subprojects/gst-plugins-good/ext/qt6/qt6glwindow.cc
index 3486c54e7927511c64988860963cbcf3b85b25ab..661187c6eb44a2a701cbdc74f4ecfe202c7e884f 100644 (file)
--- a/subprojects/gst-plugins-good/ext/qt6/qt6glwindow.cc
+++ b/subprojects/gst-plugins-good/ext/qt6/qt6glwindow.cc
@@ -103,7 +103,7 @@ Qt6GLWindow::Qt6GLWindow (QWindow * parent, QQuickWindow *src)
   this->priv->internal_format = GL_RGBA;
 
   connect (source, SIGNAL(beforeRendering()), this, SLOT(beforeRendering()), Qt::DirectConnection);
-  connect (source, SIGNAL(afterRendering()), this, SLOT(afterRendering()), Qt::DirectConnection);
+  connect (source, SIGNAL(afterFrameEnd()), this, SLOT(afterFrameEnd()), Qt::DirectConnection);
   if (source->isSceneGraphInitialized())
     source->scheduleRenderJob(new RenderJob(std::bind(&Qt6GLWindow::onSceneGraphInitialized, this)), QQuickWindow::BeforeSynchronizingStage);
   else
@@ -201,7 +201,7 @@ Qt6GLWindow::beforeRendering()
 }
 
 void
-Qt6GLWindow::afterRendering()
+Qt6GLWindow::afterFrameEnd()
 {
   gboolean ret;
   guint width, height;

diff --git a/subprojects/gst-plugins-good/ext/qt6/qt6glwindow.h b/subprojects/gst-plugins-good/ext/qt6/qt6glwindow.h
index c964da23b0fde8de5f9c17a2cda76c186894bf62..3c0fc14d978b75946d597318a0b2c5ce2651c543 100644 (file)
--- a/subprojects/gst-plugins-good/ext/qt6/qt6glwindow.h
+++ b/subprojects/gst-plugins-good/ext/qt6/qt6glwindow.h
@@ -45,7 +45,7 @@ public:
 
 private Q_SLOTS:
     void beforeRendering ();
-    void afterRendering ();
+    void afterFrameEnd ();
     void onSceneGraphInitialized ();
     void onSceneGraphInvalidated ();