GStreamer: Fix black preview window on capturesessions

Properly render the video frames we receive in capture sessions. The
pipeline for capturing should never be in a stopped state and not
deliver any video frames.

As a drive-by, convert some commented out debug output to use proper
logging.

Fixes: QTBUG-97911
Change-Id: Ie318925fa6bb9ef705b3d996f878da0bda8bf315
Reviewed-by: Piotr Srebrny <piotr.srebrny@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
(cherry picked from commit ed857e84f3c0ab90ac6dfff1aecce460f56e1a9a)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

3 files changed, 14 insertions, 11 deletions

diff --git a/src/multimedia/platform/gstreamer/common/qgstpipeline.cpp b/src/multimedia/platform/gstreamer/common/qgstpipeline.cpp
index 7a605b709..29fb0a552 100644
--- a/src/multimedia/platform/gstreamer/common/qgstpipeline.cpp
+++ b/src/multimedia/platform/gstreamer/common/qgstpipeline.cpp
@@ -138,8 +138,7 @@ private:
 
 QGstPipelinePrivate::QGstPipelinePrivate(GstBus* bus, QObject* parent)
   : QObject(parent),
-    m_bus(bus),
-    inStoppedState(true)
+    m_bus(bus)
 {
     gst_object_ref(GST_OBJECT(bus));
 
diff --git a/src/multimedia/platform/gstreamer/common/qgstvideorenderersink.cpp b/src/multimedia/platform/gstreamer/common/qgstvideorenderersink.cpp
index e9a9cf678..cbb40c13e 100644
--- a/src/multimedia/platform/gstreamer/common/qgstvideorenderersink.cpp
+++ b/src/multimedia/platform/gstreamer/common/qgstvideorenderersink.cpp
@@ -53,6 +53,8 @@
 
 #include <gst/video/video.h>
 #include <gst/video/gstvideometa.h>
+#include <qloggingcategory.h>
+#include <qdebug.h>
 
 #include "qgstutils_p.h"
 
@@ -68,6 +70,8 @@
 
 //#define DEBUG_VIDEO_SURFACE_SINK
 
+Q_LOGGING_CATEGORY(qLcGstVideoRenderer, "qt.multimedia.gstvideorenderer")
+
 QT_BEGIN_NAMESPACE
 
 QGstVideoRenderer::QGstVideoRenderer(QGstreamerVideoSink *sink)
@@ -151,7 +155,7 @@ QGstMutableCaps QGstVideoRenderer::caps()
 
 bool QGstVideoRenderer::start(GstCaps *caps)
 {
-//    qDebug() << "QGstVideoRenderer::start" << QGstCaps(caps).toString();
+    qCDebug(qLcGstVideoRenderer) << "QGstVideoRenderer::start" << QGstCaps(caps).toString();
     QMutexLocker locker(&m_mutex);
 
     if (m_active) {
@@ -224,6 +228,7 @@ void QGstVideoRenderer::flush()
 GstFlowReturn QGstVideoRenderer::render(GstBuffer *buffer)
 {
     QMutexLocker locker(&m_mutex);
+    qCDebug(qLcGstVideoRenderer) << "QGstVideoRenderer::render";
 
     m_renderReturn = GST_FLOW_OK;
     m_renderBuffer = buffer;
@@ -317,6 +322,7 @@ bool QGstVideoRenderer::handleEvent(QMutexLocker<QMutex> *locker)
         m_renderBuffer = nullptr;
         m_renderReturn = GST_FLOW_ERROR;
 
+        qCDebug(qLcGstVideoRenderer) << "QGstVideoRenderer::handleEvent(renderBuffer)" << m_active << m_sink;
         if (m_active && m_sink) {
             gst_buffer_ref(buffer);
 
@@ -328,21 +334,21 @@ bool QGstVideoRenderer::handleEvent(QMutexLocker<QMutex> *locker)
             if (meta) {
                 QRect vp(meta->x, meta->y, meta->width, meta->height);
                 if (m_format.viewport() != vp) {
-#ifdef DEBUG_VIDEO_SURFACE_SINK
-                    qDebug() << Q_FUNC_INFO << " Update viewport on Metadata: [" << meta->height << "x" << meta->width << " | " << meta->x << "x" << meta->y << "]";
-#endif \
-    //Update viewport if data is not the same
+                    qCDebug(qLcGstVideoRenderer) << Q_FUNC_INFO << " Update viewport on Metadata: [" << meta->height << "x" << meta->width << " | " << meta->x << "x" << meta->y << "]";
+                    // Update viewport if data is not the same
                     m_format.setViewport(vp);
                 }
             }
 
             if (m_sink->inStoppedState()) {
+                qCDebug(qLcGstVideoRenderer) << "    sending empty video frame";
                 m_sink->setVideoFrame(QVideoFrame());
             } else {
                 QGstVideoBuffer *videoBuffer = new QGstVideoBuffer(buffer, m_videoInfo, m_sink, m_format, memoryFormat);
                 QVideoFrame frame(videoBuffer, m_format);
                 QGstUtils::setFrameTimeStamps(&frame, buffer);
 
+                qCDebug(qLcGstVideoRenderer) << "    sending video frame";
                 m_sink->setVideoFrame(frame);
             }
 
@@ -555,10 +561,7 @@ gboolean QGstVideoRendererSink::set_caps(GstBaseSink *base, GstCaps *caps)
 {
     VO_SINK(base);
 
-#ifdef DEBUG_VIDEO_SURFACE_SINK
-    qDebug() << "set_caps:";
-    qDebug() << caps;
-#endif
+    qCDebug(qLcGstVideoRenderer) << "set_caps:" << QGstCaps(caps).toString();
 
     if (!caps) {
         sink->renderer->stop();
diff --git a/src/multimedia/platform/gstreamer/mediacapture/qgstreamermediacapture.cpp b/src/multimedia/platform/gstreamer/mediacapture/qgstreamermediacapture.cpp
index 3c1793b15..b43a4fb30 100644
--- a/src/multimedia/platform/gstreamer/mediacapture/qgstreamermediacapture.cpp
+++ b/src/multimedia/platform/gstreamer/mediacapture/qgstreamermediacapture.cpp
@@ -91,6 +91,7 @@ QGstreamerMediaCapture::QGstreamerMediaCapture()
     // This is the recording pipeline with only live sources, thus the pipeline
     // will be always in the playing state.
     gstPipeline.setState(GST_STATE_PLAYING);
+    gstPipeline.setInStoppedState(false);
 
     gstPipeline.dumpGraph("initial");
 }