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/****************************************************************************
**
** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** 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
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** use the contact form at http://qt.digia.com/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: http://www.gnu.org/copyleft/fdl.html.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\example multimedia/video/qmlvideo
\title QML Video Example
\ingroup multimedia_examples
\brief The QML Video Example demonstrates the various manipulations (move;
resize; rotate; change aspect ratio) which can be applied to QML \l{VideoOutput}
items.
\section1 Overview
This example demonstrates the various manipulations (move; resize; rotate;
change aspect ratio) which can be applied to QML \l{VideoOutput} items.
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.png
\section1 Application structure
The \l{multimedia/video/qmlvideo/qml/qmlvideo/main.qml} file creates a UI which includes
the following items:
\list
\li Two \l{multimedia/video/qmlvideo/qml/qmlvideo/Button.qml}{Button} instances, each
of which displays a filename, and can be used to launch a
\l{multimedia/video/qmlvideo/qml/qmlvideo/FileBrowser.qml}{FileBrowser}
\li An exit \l{multimedia/video/qmlvideo/qml/qmlvideo/Button.qml}{Button}
\li A \l{multimedia/video/qmlvideo/qml/qmlvideo/SceneSelectionPanel.qml}{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.png
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
\l{multimedia/ideo/qmlvideo/qml/qmlvideo/VideoBasic.qml}{VideoBasic.qml} file. As you
can see from the code, this makes use of a type of inheritance: a
\l{multimedia/video/qmlvideo/qml/qmlvideo/VideoBasic.qml}{VideoBasic} item ...
\quotefromfile multimedia/video/qmlvideo/qml/qmlvideo/VideoBasic.qml
\skipto import
\printuntil /^\}/
... is-a
\l{multimedia/video/qmlvideo/qml/qmlvideo/SceneBasic.qml}{SceneBasic} ...
\quotefromfile multimedia/video/qmlvideo/qml/qmlvideo/SceneBasic.qml
\skipto import
\printuntil contentType
\dots
\skipto Content
\printuntil content
\dots
\skipto }
\printuntil /^\}/
... which is-a
\l{multimedia/video/qmlvideo/qml/qmlvideo/Scene.qml}{Scene}:
\quotefromfile multimedia/video/qmlvideo/qml/qmlvideo/Scene.qml
\skipto import
\printuntil root
\dots
\skipto property QtObject content
\printuntil content
\dots
\skipto Button
\printuntil /^\}/
\l{multimedia/video/qmlvideo/qml/qmlvideo/SceneBasic.qml}{SceneBasic} describes the
structure and behaviour of the scene, but is agnostic of the type of content
which will be displayed - this is abstracted by
\l{multimedia/video/qmlvideo/qml/qmlvideo/Content.qml}{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
(\l{multimedia/video/qmlvideo/qml/qmlvideo/VideoBasic.qml}{VideoBasic}) and cameracontent
(\l{multimedia/video/qmlvideo/qml/qmlvideo/CameraBasic.qml}{CameraBasic}). This approach
is used to implement many of the other scenes - for example, "repeatedly slide
the content from left to right and back again" is implemented by
\l{multimedia/video/qmlvideo/qml/qmlvideo/SceneMove.qml}{SceneMove}, on which
\l{multimedia/video/qmlvideo/qml/qmlvideo/VideoMove.qml}{VideoMove} and
\l{multimedia/video/qmlvideo/qml/qmlvideo/CameraMove.qml}{CameraMove} are based.
Depending on the value of the contentType property in the top-level scene
instance, the embedded
\l{multimedia/video/qmlvideo/qml/qmlvideo/Content.qml}{Content} item creates either a
\l{MediaPlayer} or a \l{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 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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