tdf#145735 qt avmedia: Implement frame grabber

Add a new `QtFrameGrabber` class that implements
the `css::media::XFrameGrabber` interface and
return an instance of it in
`QtPlayer::createFrameGrabber`.

As there seems to be no direct way to retrieve
the image/frame of a video at a certain point
in time, create a separate `QMediaPlayer` instance
for the `QtFrameGrabber`, set a video sink, connect
to its `&QVideoSink::videoFrameChanged` signal and
start playing the video (and stop it again once the
first frame has been received) in order to retrieve
a corresponding frame.

From that `QVideoFrame`, a `QImage` can be retrieved
that can then be converted to an `XGraphic`.

With this in place, a frame from the actual video
is now displaced in Impress in non-presentation
mode instead of just a generic "video icon" placeholder
when opening a presentation containing a video,
(e.g. attachment 145517 from tdf#120452) when the
qt6 VCL plugin is in use.

Change-Id: I3bba3c0fb62a219ac632ceed03ec17f9078f18d0
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/168255
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

avmedia/CustomTarget_avmediaqt6_moc.mk

@@ -10,6 +10,7 @@
 $(eval $(call gb_CustomTarget_CustomTarget,avmedia/source/qt6))
 
 $(call gb_CustomTarget_get_target,avmedia/source/qt6) : \
+	$(gb_CustomTarget_workdir)/avmedia/source/qt6/QtFrameGrabber.moc \
 	$(gb_CustomTarget_workdir)/avmedia/source/qt6/QtPlayer.moc
 
 

avmedia/Library_avmediaqt6.mk

@@ -37,6 +37,7 @@ $(eval $(call gb_Library_use_libraries,avmediaqt6,\
 
 $(eval $(call gb_Library_add_exception_objects,avmediaqt6,\
 	avmedia/source/qt6/gstwindow \
+	avmedia/source/qt6/QtFrameGrabber \
 	avmedia/source/qt6/QtManager \
 	avmedia/source/qt6/QtPlayer \
 ))

avmedia/source/qt6/QtFrameGrabber.cxx

@@ -0,0 +1,106 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <QtCore/QBuffer>
+#include <QtCore/QByteArray>
+
+#include <sal/log.hxx>
+#include <vcl/filter/PngImageReader.hxx>
+#include <vcl/graph.hxx>
+#include <vcl/image.hxx>
+#include <vcl/scheduler.hxx>
+
+#include "QtFrameGrabber.hxx"
+#include <QtFrameGrabber.moc>
+
+using namespace ::com::sun::star;
+
+namespace
+{
+inline OUString toOUString(const QString& s)
+{
+    return OUString(reinterpret_cast<const sal_Unicode*>(s.data()), s.length());
+}
+
+uno::Reference<css::graphic::XGraphic> toXGraphic(const QImage& rImage)
+{
+    QByteArray aData;
+    QBuffer aBuffer(&aData);
+    rImage.save(&aBuffer, "PNG");
+
+    SvMemoryStream aStream(aData.data(), aData.size(), StreamMode::READ);
+    vcl::PngImageReader aReader(aStream);
+    Graphic aGraphic;
+    aReader.read(aGraphic);
+
+    return aGraphic.GetXGraphic();
+}
+}
+
+namespace avmedia::qt
+{
+QtFrameGrabber::QtFrameGrabber(const QUrl& rSourceUrl)
+    : m_bWaitingForFrame(false)
+{
+    m_xMediaPlayer = std::make_unique<QMediaPlayer>();
+    m_xMediaPlayer->setSource(rSourceUrl);
+
+    m_xVideoSink = std::make_unique<QVideoSink>();
+    m_xMediaPlayer->setVideoSink(m_xVideoSink.get());
+
+    connect(m_xMediaPlayer.get(), &QMediaPlayer::errorOccurred, this,
+            &QtFrameGrabber::onErrorOccured, Qt::BlockingQueuedConnection);
+}
+
+void QtFrameGrabber::onErrorOccured(QMediaPlayer::Error eError, const QString& rErrorString)
+{
+    std::lock_guard aLock(m_aMutex);
+
+    SAL_WARN("avmedia", "Media playback error occured when trying to grab frame: "
+                            << toOUString(rErrorString) << ", code: " << eError);
+
+    m_bWaitingForFrame = false;
+}
+
+void QtFrameGrabber::onVideoFrameChanged(const QVideoFrame& rFrame)
+{
+    std::lock_guard aLock(m_aMutex);
+
+    disconnect(m_xVideoSink.get(), &QVideoSink::videoFrameChanged, this,
+               &QtFrameGrabber::onVideoFrameChanged);
+
+    const QImage aImage = rFrame.toImage();
+    m_xGraphic = toXGraphic(aImage);
+    m_bWaitingForFrame = false;
+}
+
+css::uno::Reference<css::graphic::XGraphic> SAL_CALL QtFrameGrabber::grabFrame(double fMediaTime)
+{
+    std::lock_guard aLock(m_aMutex);
+
+    m_xMediaPlayer->setPosition(fMediaTime * 1000);
+
+    // in order to get a video frame, connect to videoFrameChanged signal and start playing
+    // until the first frame has been received
+    m_bWaitingForFrame = true;
+    connect(m_xVideoSink.get(), &QVideoSink::videoFrameChanged, this,
+            &QtFrameGrabber::onVideoFrameChanged, Qt::BlockingQueuedConnection);
+    m_xMediaPlayer->play();
+    while (m_bWaitingForFrame)
+        Scheduler::ProcessEventsToIdle();
+    m_xMediaPlayer->stop();
+
+    uno::Reference<css::graphic::XGraphic> xGraphic = m_xGraphic;
+    m_xGraphic.clear();
+    return xGraphic;
+}
+
+}; // namespace
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */

avmedia/source/qt6/QtFrameGrabber.hxx

@@ -0,0 +1,50 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#pragma once
+
+#include <mutex>
+
+#include <QtCore/QObject>
+#include <QtMultimedia/QMediaPlayer>
+#include <QtMultimedia/QVideoFrame>
+#include <QtMultimedia/QVideoSink>
+
+#include <com/sun/star/graphic/XGraphic.hpp>
+#include <com/sun/star/media/XFrameGrabber.hpp>
+#include <comphelper/compbase.hxx>
+
+namespace avmedia::qt
+{
+class QtFrameGrabber : public QObject, public ::cppu::WeakImplHelper<css::media::XFrameGrabber>
+{
+    Q_OBJECT
+
+private:
+    std::unique_ptr<QVideoSink> m_xVideoSink;
+    std::unique_ptr<QMediaPlayer> m_xMediaPlayer;
+
+    std::recursive_mutex m_aMutex;
+    bool m_bWaitingForFrame;
+    css::uno::Reference<css::graphic::XGraphic> m_xGraphic;
+
+public:
+    QtFrameGrabber(const QUrl& rSourceUrl);
+
+    virtual css::uno::Reference<css::graphic::XGraphic>
+        SAL_CALL grabFrame(double fMediaTime) override;
+
+private slots:
+    void onErrorOccured(QMediaPlayer::Error eError, const QString& rErrorString);
+    void onVideoFrameChanged(const QVideoFrame& rFrame);
+};
+
+} // namespace avmedia::qt
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */

avmedia/source/qt6/QtPlayer.cxx

@@ -27,6 +27,7 @@
 #include <vcl/timer.hxx>
 
 #include <gstwindow.hxx>
+#include "QtFrameGrabber.hxx"
 #include "QtPlayer.hxx"
 
 #include <QtPlayer.moc>
@@ -229,7 +230,13 @@ uno::Reference<::media::XPlayerWindow>
     return xRet;
 }
 
-uno::Reference<media::XFrameGrabber> SAL_CALL QtPlayer::createFrameGrabber() { return nullptr; }
+uno::Reference<media::XFrameGrabber> SAL_CALL QtPlayer::createFrameGrabber()
+{
+    osl::MutexGuard aGuard(m_aMutex);
+
+    rtl::Reference<QtFrameGrabber> xFrameGrabber = new QtFrameGrabber(m_xMediaPlayer->source());
+    return xFrameGrabber;
+}
 
 void SAL_CALL
 QtPlayer::addPlayerListener(const css::uno::Reference<css::media::XPlayerListener>& rListener)