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/****************************************************************************
**
** Copyright (C) 2015 The Qt Company Ltd.
** Contact: http://www.qt.io/licensing/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** 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 Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: https://www.gnu.org/licenses/fdl-1.3.html.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\example multimedia/video/qmlvideo
\title QML Video Example
\ingroup multimedia_examples
\brief Transforming video and camera viewfinder content.
\e{QML Video} demonstrates the various transformations (move; resize; rotate;
change aspect ratio) that can be applied to QML \l VideoOutput and \l Camera
types.
It also shows how native code can be combined with QML to implement more
advanced functionality - in this case, C++ code is used to calculate the QML
frame rate. This value is rendered in QML in a semi-transparent item
overlaid on the video content.
The following image shows the application executing the video-overlay scene,
which creates a dummy overlay item (just a semi-transparent \l{Rectangle}),
which moves across the \l{VideoOutput} item.
\image qmlvideo-overlay.jpg
\include examples-run.qdocinc
\section1 Application Structure
The \c main.qml file creates a UI which includes the following items:
\list
\li Two \c Button instances, each of which displays a filename, and can be
used to launch a \c FileBrowser.
\li An exit \c Button.
\li A \c SceneSelectionPanel, which is a flickable list displaying the
available scenes.
\li At the lower left, an item which displays the QML repainting rate - the
upper number is the instantaneous frame rate and the lower number is the
average over the past second.
\endlist
\image qmlvideo-menu.jpg
Each scene in the flickable list is implemented in its own QML file - for
example the video-basic scene (which just displays a static \l{VideoOutput}
in the center of the screen) is implemented in the \c VideoBasic.qml file. As
you can see from the code, this makes use of a type of inheritance; a
\c VideoBasic item ...
\quotefromfile multimedia/video/qmlvideo/qml/qmlvideo/VideoBasic.qml
\skipto import
\printuntil /^\}/
... is of type \c SceneBasic ...
\quotefromfile multimedia/video/qmlvideo/qml/qmlvideo/SceneBasic.qml
\skipto import
\printuntil contentType
\dots
\skipto Content
\printuntil content
\dots
\skipto }
\printuntil /^\}/
... which itself is a \c Scene:
\quotefromfile multimedia/video/qmlvideo/qml/qmlvideo/Scene.qml
\skipto import
\printuntil root
\dots
\skipto property QtObject content
\printuntil content
\dots
\skipto Button
\printuntil /^\}/
\c SceneBasic describes the structure and behavior of the scene, but is
agnostic of the type of content which will be displayed - this is abstracted
by \c Content.
This pattern allows us to define a particular use case (in this case, simply
display a static piece of content), and then instantiate that use case for
both video content (\c {VideoBasic}) and camera content \c ({CameraBasic}).
This approach is used to implement many of the other scenes - for example,
\e {"repeatedly slide the content from left to right and back again"} is
implemented by \c SceneMove, on which \c VideoMove and \c CameraMove are based.
Depending on the value of the contentType property in the top-level scene
instance, the embedded \c Content item creates either a
\l[QML]{MediaPlayer} or a \l[QML]{Camera} item.
\section1 Calculating and Displaying QML Painting Rate
\input multimedia/doc/src/examples/video-qml-paint-rate.qdocinc
All that remains is to connect the afterRendering() signal of the QQuickView
object to a JavaScript function, which will eventually call
\c frequencyItem.notify():
\quotefromfile multimedia/video/qmlvideo/main.cpp
\skipto QGuiApplication
\printuntil ;
\dots
\skipto QQuickItem
\printuntil ;
\dots
\skipto QObject::connect
\printuntil SLOT(qmlFramePainted()));
*/
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