Move the gstreamer video output handling into it's own class

This will allow us to re-use the implementation for the
capture session.

Change-Id: I383133b7f5710379566768c372de0c1e78a56855
Reviewed-by: Doris Verria <doris.verria@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 146 insertions, 0 deletions

diff --git a/src/multimedia/platform/gstreamer/common/qgstreamervideooutput.cpp b/src/multimedia/platform/gstreamer/common/qgstreamervideooutput.cpp
new file mode 100644
index 000000000..939e88599
--- /dev/null
+++ b/src/multimedia/platform/gstreamer/common/qgstreamervideooutput.cpp
@@ -0,0 +1,146 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <private/qgstreamervideooutput_p.h>
+#include <private/qgstreamervideorenderer_p.h>
+
+#include <QtCore/qloggingcategory.h>
+#include <qthread.h>
+
+Q_LOGGING_CATEGORY(qLcMediaVideoOutput, "qt.multimedia.videooutput")
+
+QT_BEGIN_NAMESPACE
+
+QGstreamerVideoOutput::QGstreamerVideoOutput(QObject *parent)
+    : QObject(parent),
+      gstVideoOutput("videoOutput")
+{
+    videoQueue = QGstElement("queue", "videoQueue");
+    videoConvert = QGstElement("videoconvert", "videoConvert");
+    videoScale = QGstElement("videoscale", "videoScale");
+    videoSink = QGstElement("fakesink", "fakeVideoSink");
+    gstVideoOutput.add(videoQueue, videoConvert, videoScale, videoSink);
+    videoQueue.link(videoConvert, videoScale, videoSink);
+
+    gstVideoOutput.addGhostPad(videoQueue, "sink");
+}
+
+QGstreamerVideoOutput::~QGstreamerVideoOutput()
+{
+}
+
+static QGstElement getSink(QGstreamerVideoRenderer *output)
+{
+    QGstElement newSink;
+    if (output && output->isReady())
+        newSink = output->videoSink();
+
+    if (newSink.isNull())
+        newSink = QGstElement("fakesink", "fakevideosink");
+
+    return newSink;
+}
+
+void QGstreamerVideoOutput::setVideoSurface(QAbstractVideoSurface *surface)
+{
+    if (!m_videoOutput) {
+        m_videoOutput = new QGstreamerVideoRenderer;
+        qCDebug(qLcMediaVideoOutput) << Q_FUNC_INFO;
+        connect(m_videoOutput, SIGNAL(sinkChanged()),
+                this, SLOT(updateVideoRenderer()));
+    }
+
+    m_videoOutput->setSurface(surface);
+
+    newVideoSink = getSink(m_videoOutput);
+    if (newVideoSink == videoSink) {
+        newVideoSink = {};
+        return;
+    }
+    gstVideoOutput.add(newVideoSink);
+
+    qCDebug(qLcMediaVideoOutput) << "setVideoSurface: Reconfiguring video output" << QThread::currentThreadId();
+
+    auto state = gstPipeline.state();
+
+    if (state != GST_STATE_PLAYING) {
+        changeVideoOutput();
+        return;
+    }
+
+    // This doesn't quite work, as we're be getting the callback in another thread where state changes aren't allowed.
+    auto pad = videoScale.staticPad("src");
+    pad.addProbe<&QGstreamerVideoOutput::prepareVideoOutputChange>(this, GST_PAD_PROBE_TYPE_IDLE);
+}
+
+void QGstreamerVideoOutput::setIsPreview()
+{
+    // configures the queue to be fast and lightweight for camera preview
+    // also avoids blocking the queue in case we have an encodebin attached to the tee as well
+    videoQueue.set("leaky", 2 /*downstream*/);
+    videoQueue.set("silent", true);
+    videoQueue.set("max-size-buffers", 1);
+    videoQueue.set("max-size-bytes", 0);
+    videoQueue.set("max-size-time", 0);
+}
+
+void QGstreamerVideoOutput::changeVideoOutput()
+{
+    qCDebug(qLcMediaVideoOutput) << "Changing video output" << QThread::currentThreadId();
+
+    auto state = videoSink.state();
+    videoSink.setState(GST_STATE_NULL);
+    gstVideoOutput.remove(videoSink);
+    videoSink = newVideoSink;
+    videoScale.link(videoSink);
+    videoSink.setState(state);
+    newVideoSink = {};
+}
+
+void QGstreamerVideoOutput::prepareVideoOutputChange(const QGstPad &/*pad*/)
+{
+    qCDebug(qLcMediaVideoOutput) << "Reconfiguring video output" << QThread::currentThreadId();
+
+    gstPipeline.setState(GST_STATE_PAUSED);
+    changeVideoOutput();
+    gstPipeline.setState(GST_STATE_PLAYING);
+}
+
+
+QT_END_NAMESPACE