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diff --git a/doc/src/multimedia.qdoc b/doc/src/multimedia.qdoc new file mode 100644 index 000000000..25c42f5fe --- /dev/null +++ b/doc/src/multimedia.qdoc @@ -0,0 +1,470 @@ +/**************************************************************************** +** +** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies). +** All rights reserved. +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the documentation of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:FDL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the Technology Preview License Agreement accompanying +** this package. +** +** GNU Free Documentation License +** 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. +** +** If you have questions regarding the use of this file, please contact +** Nokia at qt-info@nokia.com. +** $QT_END_LICENSE$ +** +****************************************************************************/ + + +/*! + \group multimedia + \title QtMobility Multimedia + APIs to play and record media, and manage a collection of media content. +*/ + +// XXX title sucks +// XXX move backend stuff away +// XXX move QML stuff up +// XXX more introductory material +// XXX terminology +// XXX separate pages for audio, video, camera, radio, metadata +// control, mediaobject etc stuff +// symbian/harmattan specific pages + +/*! + +\page multimedia.html +\title Multimedia +\brief Provides a set of APIs to play and record media, and manage a +collection of media content. +\ingroup mobility + +Multimedia provides a set of APIs that allow the developer to play, record +and manage a collection of media content. It is dependent on the +QtMultimediaKit module. QtMultimediaKit is the recommended API to build multimedia +applications using Qt. The Phonon API is no longer recommended. + +\tableofcontents + +\section1 No Special Namespace + +Unlike the other APIs in QtMobility, the Multimedia API is \i not in the +\i QtMobility namespace. + +\section1 Overview + +This API delivers an easy to use interface to multimedia functions. The +developer can use the API to display an image, or a video, record sound or play a +multimedia stream. + +There are several benefits this API brings to Qt. Firstly, the +developer can now implement fundamental multimedia functions with minimal +code, mostly because they are already implemented. Also there is a great +deal of flexibility with the media source or the generated multimedia. The +source file does not need to be local to the device, it could be streamed +from a remote location and identified by a URL. Finally, many different +codecs are supported 'out +of the box'. + +The supplied \l {qtmultimediakit examples}{examples} give a good idea at the ease of use of the API. When +the supporting user interface code is ignored we can see that functionality +is immediately available with minimal effort. + +\section2 Audio + +The Audio Recorder example is a good introduction to the basic use of the API. We will use snippets from this example to illustrate how to use the +API to quickly build functionality. + +The first step is to demonstrate recording audio to a file. When recording from an audio source there are a number of things we may want to control beyond the essential user interface. We may want a particular encoding of the file, MP3 or Ogg Vorbis for instance, or select a different input source. The user may modify the bitrate, number of channels, quality and sample rate. Here the example will only modify the codec and the source device, since they are essential. + +To begin, the developer sets up a source and a recorder object. A +\l{QAudioCaptureSource} object is created and used to initialize a \l{QMediaRecorder} object. The output file name is then set for the \l{QMediaRecorder} object. + +\code + audiosource = new QAudioCaptureSource; + capture = new QMediaRecorder(audiosource); + + capture->setOutputLocation(QUrl("test.raw")); +\endcode + +A list of devices is needed so that an input can be selected in the user interface + +\code + for(int i = 0; i < audiosource->deviceCount(); i++) + deviceBox->addItem(audiosource->name(i)); +\endcode + +and a list of the supported codecs for the user to select a codec, + +\code + QStringList codecs = capture->supportedAudioCodecs(); + for(int i = 0; i < codecs.count(); i++) + codecsBox->addItem(codecs.at(i)); +\endcode + +To set the selected device or codec just use the index of the device or codec by calling the setter in \i {audiosource} or \i {capture} as appropriate, for example, + +\code + audiosource->setSelectedDevice(i); + ... + capture->setAudioCodec(codecIdx); +\endcode + +Now start recording by using the \l {QMediaRecorder}{record()} function from the new \l{QMediaRecorder} object + +\code + capture->record(); +\endcode + +And stop recording by calling the matching function \l {QMediaRecorder::stop()}{stop()} in \l{QMediaRecorder}. + +\code + capture->stop(); +\endcode + +How then would this audio file be played? The \l {QMediaPlayer} class will be +used as a generic player. Since the player can play both video and audio files the interface will be more complex, but for now the example will concentrate on the audio aspect. + +Playing the file is simple: create a player object, pass in the filename, set +the volume or other parameters, then play. Not forgetting that the code will +need to be hooked up to the user interface. + +\code + QMediaPlayer *player = new QMediaPlayer; + ... + player->setMedia(QUrl::fromLocalFile("test.raw")); + player->setVolume(50); + player->play(); +\endcode + +The filename does not have to be a local file. It could be a URL to a +remote resource. Also by using the \l{QMediaPlaylist} class from this API +we can play a list of local or remote files. The \l{QMediaPlaylist} +class supports constructing, managing and playing playlists. + +\code + player = new QMediaPlayer; + + playlist = new QMediaPlaylist(player); + playlist->addMedia(QUrl("http://example.com/myfile1.mp3")); + playlist->addMedia(QUrl("http://example.com/myfile2.mp3")); + ... + playlist->setCurrentPosition(1); + player->play(); +\endcode + +To manipulate the playlist there are the usual management functions (which are in fact slots): previous, next, setCurrentPosition and shuffle. Playlists can be built, saved and loaded using the API. + + + +\section2 Video + +Continuing with the example discussed for an Audio recorder/player, we can use this to show how to play video files with little change to the code. + +Moving from audio to video requires few changes in the sample code. To play a +video playlist the code can be changed to include another new QtMobility +Project class: \l{QVideoWidget}. This class enables control of a video +resource with signals and slots for the control of brightness, contrast, +hue, saturation and full screen mode. + +\code + player = new QMediaPlayer; + + playlist = new QMediaPlaylist(player); + playlist->addMedia(QUrl("http://example.com/myclip1.mp4")); + playlist->addMedia(QUrl("http://example.com/myclip2.mp4")); + ... + widget = new QVideoWidget(player); + widget->show(); + + playlist->setCurrentPosition(1); + player->play(); +\endcode + +The \l {player}{Player} example does things a bit differently to our sample +code. Instead of using a QVideoWidget object directly, the Player example +has a \i {VideoWidget} class that inherits from QVideoWidget. This means +that functions can be added to provide functions such as full screen display, +either on a double click or on a particular keypress. + +\snippet ../../demos/player/player.cpp 2 + + +\section2 Radio + +QRadioTunerControl is a pure virtual base class that will be the basis for +any platform specific radio device control. When the functions are +implemented the developer will be able to quickly produce an application +that supports the typical uses of an FM radio including tuning, volume, +start, stop and various other controls. + +\section1 Extending the API for Symbian and Maemo + + +For the developer who wishes to extend the functionality of the Multimedia +classes there are several classes of particular importance. The default +classes are QMediaService, QMediaServiceProvider and QMediaControl. + +Basically, the idea is that to use the Multimedia API you would use these +three classes or classes derived from them as follows + + \list + \o \l QMediaServiceProvider is used by the top level client class to request a service. The top level class knowing what kind of service it needs. + + \o \l QMediaService provides a service and when asked by the top level object, say a component, will return a QMediaControl object. + + \o \l QMediaControl allows the control of the service using a known interface. + \endlist + +Consider a developer creating, for example, a media player class called MyPlayer. +It may have special requirements beyond ordinary media players and so may +need a custom service and a custom control. We can subclass \l QMediaServiceProvider +to create our MyServiceProvider class. Also we will create a +MyMediaService, and the MyMediaControl to manipulate the media service. + +The MyPlayer object calls MyServiceProvider::requestService() to get an +instance of MyMediaService. Then the MyPlayer object calls this service +object it has just received and calling \l {QMediaService::requestControl()}{requestControl()} +it will receive the control object derived from QMediaControl. Now we have +all the parts necessary for our media application. We have the service +provider, the service it provides and the control used to manipulate the +service. Since our MyPlayer object has instances of the service and its +control then it would be possible for these to be used by associated classes +that could do additional actions, perhaps with their own control since the +parameter to requestControl() is a c-type string, \i {const char *}, for the +interface. + + +\section2 Adding a Media Service Provider + +The base class for creating new service providers is \l{QMediaServiceProvider}. +The user must implement the \l{QMediaServiceProvider::requestService()}{requestService()} +function + +\code + QMediaService* requestService(const QByteArray &type, const QMediaServiceProviderHint &hint); +\endcode + +The details of implementation will depend on the provider. Looking at the +class \l QMediaServiceProvider for the default implementation. Notice that +\l {QMediaServiceProvider::requestService()}{requestService()} uses the +\l QMediaServiceProviderHint to look for the appropriate plugin and then to +insert it into the plugin map. However, for a specific service provider there +is probably no need for this approach, it will simply depend on what the +developer wants to implement. + +Other methods that may be overloaded +\code + void releaseService(QMediaService *service); + + QtMediaServices::SupportEstimate hasSupport(const QByteArray &serviceType, + const QString &mimeType, + const QStringList& codecs, + int flags) const; + + QStringList supportedMimeTypes(const QByteArray &serviceType, int flags) const; + + QList<QByteArray> devices(const QByteArray &serviceType) const; + + QString deviceDescription(const QByteArray &serviceType, const QByteArray &device); +\endcode + +The choice of what needs to be done depends on what the developer wishes to do with the service. + + +\section1 Camera Support + +Creating still images and video. + +\section2 Still Images + +In order to capture an image we need to create a \l QCamera object and use +it to initialize a \l QVideoWidget, so we can see where the camera is +pointing - a viewfinder. The camera object is also used to initialize a new +QCameraImageCapture object, \i imageCapture. All that is then needed is to start +the camera, lock it so that the settings are not changed while the image +capture occurs, capture the image, and finally unlock the camera ready for +the next photo. + + \code + camera = new QCamera; + viewFinder = new QCameraViewfinder(); + viewFinder->show(); + + camera->setViewfinder(viewFinder); + + imageCapture = new QCameraImageCapture(camera); + + camera->setCaptureMode(QCamera::CaptureStillImage); + camera->start(); + + //on half pressed shutter button + camera->searchAndLock(); + + ... + + //on shutter button pressed + imageCapture->capture(); + + //on shutter button released + camera->unlock(); + \endcode + +\note Alternatively, we could have used a QGraphicsVideoItem as a viewfinder. + + +\section2 Video Clips + +Previously we saw code that allowed the capture of a still image. Recording +video requires the use of a \l QMediaRecorder object and a \l +QAudioCaptureSource for sound. + +To record video we need a camera object, as before, a media recorder and a +viewfinder object. The media recorder object will need to be initialized. + + \code + camera = new QCamera; + mediaRecorder = new QMediaRecorder(camera); + + camera->setCaptureMode(QCamera::CaptureVideo); + camera->start(); + + //on shutter button pressed + mediaRecorder->record(); + \endcode + +Signals from the \i mediaRecorder can be connected to slots to react to +changes in the state of the recorder or error events. Recording itself +starts with the \l {QMediaRecorder::record()}{record()} function of +mediaRecorder being called, this causes the signal \l +{QMediaRecorder::stateChanged()}{stateChanged()} to be emitted. The +recording process can be changed with the \l {QMediaRecorder::record()}{record()}, +\l {QMediaRecorder::pause()}{pause()}, \l {QMediaRecorder::stop()}{stop()} and +\l {QMediaRecorder::setMuted()}{setMuted()} slots in \l QMediaRecorder. + +When the camera is in video mode, as decided by the application, then as the +shutter button is pressed the camera is locked as before but instead the +\l {QMediaRecorder::record()}{record()} function in \l QMediaRecorder is used. + + + +\section2 Focus + +Focusing is managed by the classes \l QCameraFocus and \l QCameraFocusControl. +QCameraFocus allows the developer to set the general policy by means of the +enums for the \l {QCameraFocus::FocusMode}{FocusMode} and the +\l {QCameraFocus::FocusPointMode}{FocusPointMode}. +\l {QCameraFocus::FocusMode}{FocusMode} deals with +settings such as \l {QCameraFocus::FocusMode}{AutoFocus}, +\l {QCameraFocus::FocusMode}{ContinuousFocus} and +\l {QCameraFocus::FocusMode}{InfinityFocus}, whereas +\l {QCameraFocus::FocusPointMode}{FocusPointMode} deals with the various focus zones within the view. +\l {QCameraFocus::FocusPointMode}{FocusPointMode} has support for face +recognition, center focus and a custom focus where the focus point can be specified. + + + +\section2 Canceling Asynchronous Operations + +Various operations such as image capture and auto focusing occur +asynchrously. These operations can often be cancelled by the start of a new +operation as long as this is supported by the backend. For image capture, +the operation can be cancelled by calling +\l {QCameraImageCapture::cancelCapture()}{cancelCapture()}. For \l {QCameraFocus::FocusMode}{auto-focus}, +\l {QCameraExposure::ExposureMode}{auto-exposure} or \l {QCameraImageProcessing::WhiteBalanceMode}{white balance} +cancellation can be done by calling \l {QCamera::unlock()}{unlock}(QCamera::LockFocus). + + + +\section2 Camera Controls + + \table + \header + \o Control Name + \o Description + \row + \o camera + \o The interface for system camera devices + \row + \o exposure + \o Includes: flash mode; flash power; metering mode; aperture; shutter speed, iso setting + \row + \o focus + \o Includes: optical zoom; digital zoom; focus point; focus zones + \row + \o image processing + \o White balance; contrast; saturation; sharpen; denoise + \row + \o locks + \o Handles the locking and unlocking of camera devices + \endtable + + +\section2 Classes +\annotatedlist camera + + + + +\target qtmultimediakit examples +\section1 Examples + +\section2 Record a Sound Source + +\l{audiorecorder}{AudioRecorder} is a demonstration of the discovery of +the supported devices and codecs and the use of recording functions in the +QMediaRecorder class. + +\section2 Play a Media File + +The \l{player}{Player} example is a simple multimedia player. Select a +video file to play, stop, pause, show in fullscreen or manipulate various +image attributes using the Color Options button. + +\section2 Slide Show + +The \l{slideshow}{Slide Show} shows the use of the QMediaImageViewer and +QVideoWidget classes. + +\section2 Camera Example + +The \l{Camera Example} shows how use the QtMultimediaKit API to quickly +write a camera application in C++. + +\section2 QML Camera Example + +The \l {QML Camera Example} demonstrates still image capture and controls +using the QML plugin. Video recording is not currently available. + + +\section1 Reference documentation + +\section2 Main classes + +\annotatedlist multimedia + + +\section2 Classes for service implementers. + +\annotatedlist multimedia-serv + +\section2 QML Elements +\list +\o \l {SoundEffect}{SoundEffect: Low Latency Sound Effects} +\o \l {Audio}{Audio: Music playback} +\o \l {Video}{Video: Video playback} +\endlist +*/ + + + |