MediaObject Class Reference

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Detailed Description

Interface for media playback of a given URL.

This class is the most important class in Phonon. Use it to open a media file at an arbitrary location, a CD or DVD or to stream media data from the application to the backend.

This class controls the state (play, pause, stop, seek) and you can use it to get a lot of information about the media data.

Notice that most functions of this class are asynchronous. That means if you call play() the object only starts playing when the stateChanged() signal tells you that the object changed into PlayingState. The states you can expect are documented for those methods.

A common usage example is the following:

 media = new MediaObject(this);
 connect(media, SIGNAL(finished()), SLOT(slotFinished());
 media->setCurrentSource("/home/username/music/filename.ogg");
 media->play();

If you want to play more than one media file (one after another) you can either tell MediaObject about all those files

 media->setCurrentSource(":/sounds/startsound.ogg");
 media->enqueue("/home/username/music/song.mp3");
 media->enqueue(":/sounds/endsound.ogg");

or provide the next file just in time:

   media->setCurrentSource(":/sounds/startsound.ogg");
   connect(media, SIGNAL(aboutToFinish()), SLOT(enqueueNextSource()));
 }

 void enqueueNextSource()
 {
   media->enqueue("/home/username/music/song.mp3");
 }

Author:

Matthias Kretz <kretz@kde.org>

Definition at line 85 of file mediaobject.h.

#include <Phonon/MediaObject>

Inheritance diagram for MediaObject:

List of all members.

Public Slots
void	setTickInterval (qint32 newTickInterval)
void	play ()
	Requests playback of the media data to start.
void	pause ()
	Requests playback to pause.
void	stop ()
	Requests playback to stop.
void	seek (qint64 time)
	Requests a seek to the time indicated.
void	clear ()
	Stops and removes all playing and enqueued media sources.
Signals
void	stateChanged (Phonon::State newstate, Phonon::State oldstate)
	Emitted when the state of the MediaObject has changed.
void	tick (qint64 time)
	This signal gets emitted every tickInterval milliseconds.
void	metaDataChanged ()
	This signal is emitted whenever the audio/video data that is being played is associated with new meta data.
void	seekableChanged (bool isSeekable)
	Emitted whenever the return value of isSeekable() changes.
void	hasVideoChanged (bool hasVideo)
	Emitted whenever the return value of hasVideo() changes.
void	bufferStatus (int percentFilled)
	Tells about the status of the buffer.
void	finished ()
	Emitted when the object has finished playback.
void	currentSourceChanged (const Phonon::MediaSource &newSource)
	Emitted when the MediaObject makes a transition to the next MediaSource in the queue().
void	aboutToFinish ()
	Emitted before the playback of the whole queue stops.
void	prefinishMarkReached (qint32 msecToEnd)
	Emitted when there are only msecToEnd milliseconds left for playback.
void	totalTimeChanged (qint64 newTotalTime)
	This signal is emitted as soon as the total time of the media file is known or has changed.
Public Member Functions
	~MediaObject ()
	Destroys the MediaObject.
State	state () const
	Get the current state.
bool	hasVideo () const
	Check whether the media data includes a video stream.
bool	isSeekable () const
	Check whether the current media may be seeked.
qint32	tickInterval () const
QStringList	metaData (const QString &key) const
	Returns the strings associated with the given key.
QStringList	metaData (Phonon::MetaData key) const
	Returns the strings associated with the given key.
QMultiMap< QString, QString >	metaData () const
	Returns all meta data.
QString	errorString () const
	Returns a human-readable description of the last error that occurred.
ErrorType	errorType () const
	Tells your program what to do about the error.
MediaSource	currentSource () const
	Returns the current media source.
void	setCurrentSource (const MediaSource &source)
	Set the media source the MediaObject should use.
QList< MediaSource >	queue () const
	Returns the queued media sources.
void	setQueue (const QList< MediaSource > &sources)
	Set the MediaSources to play when the current media has finished.
void	setQueue (const QList< QUrl > &urls)
	Set the MediaSources to play when the current media has finished.
void	enqueue (const MediaSource &source)
	Appends one source to the queue.
void	enqueue (const QList< MediaSource > &sources)
	Appends multiple sources to the queue.
void	enqueue (const QList< QUrl > &urls)
	Appends multiple sources to the queue.
void	clearQueue ()
	Clears the queue of sources.
qint64	currentTime () const
	Get the current time (in milliseconds) of the file currently being played.
qint64	totalTime () const
	Get the total time (in milliseconds) of the file currently being played.
qint64	remainingTime () const
	Get the remaining time (in milliseconds) of the file currently being played.
qint32	prefinishMark () const
void	setPrefinishMark (qint32 msecToEnd)
qint32	transitionTime () const
void	setTransitionTime (qint32 msec)
Properties
qint32	transitionTime
	Defines the time between media sources.
qint32	prefinishMark
	Get a signal before playback finishes.
qint32	tickInterval
	The time interval in milliseconds between two ticks.
Friends
class	FrontendInterfacePrivate

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Constructor & Destructor Documentation

~MediaObject

(

)

Destroys the MediaObject.

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Member Function Documentation

State state

(

)

const

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Get the current state.

Returns:

The state of the object.

See also:

State

stateChanged

bool hasVideo

(

)

const

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Check whether the media data includes a video stream.

Warning:

This information cannot be known immediately. It is best to also listen to the hasVideoChanged signal.

   connect(media, SIGNAL(hasVideoChanged(bool)), hasVideoChanged(bool));
   media->setCurrentSource("somevideo.avi");
   media->hasVideo(); // returns false;
 }

 void hasVideoChanged(bool b)
 {
   // b == true
   media->hasVideo(); // returns true;
 }

Returns:

true if the media contains video data. false otherwise.

See also:

hasVideoChanged

bool isSeekable

(

)

const

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Check whether the current media may be seeked.

Warning:

This information cannot be known immediately. It is best to also listen to the seekableChanged signal.

   connect(media, SIGNAL(seekableChanged(bool)), seekableChanged(bool));
   media->setCurrentSource("somevideo.avi");
   media->isSeekable(); // returns false;
 }

 void seekableChanged(bool b)
 {
   // b == true
   media->isSeekable(); // returns true;
 }

Returns:

true when the current media may be seeked. false otherwise.

See also:

seekableChanged()

qint32 tickInterval

(

)

const

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QStringList metaData

(

const QString &

key

)

const

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Returns the strings associated with the given key.

Backends should use the keys specified in the Ogg Vorbis documentation: http://xiph.org/vorbis/doc/v-comment.html

Therefore the following should work with every backend:

A typical usage looks like this:

 setMetaArtist (media->metaData("ARTIST"     ));
 setMetaAlbum  (media->metaData("ALBUM"      ));
 setMetaTitle  (media->metaData("TITLE"      ));
 setMetaDate   (media->metaData("DATE"       ));
 setMetaGenre  (media->metaData("GENRE"      ));
 setMetaTrack  (media->metaData("TRACKNUMBER"));
 setMetaComment(media->metaData("DESCRIPTION"));

For Audio CDs you can query

 metaData("MUSICBRAINZ_DISCID");

to get a DiscID hash that you can use with the MusicBrainz service: http://musicbrainz.org/doc/ClientHOWTO

QStringList metaData

(

Phonon::MetaData

key

)

const

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Returns the strings associated with the given key.

Same as above except that the keys are defined in the Phonon::MetaData enum.

QMultiMap<QString, QString> metaData

(

)

const

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Returns all meta data.

QString errorString

(

)

const

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Returns a human-readable description of the last error that occurred.

ErrorType errorType

(

)

const

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Tells your program what to do about the error.

See also:

Phonon::ErrorType

MediaSource currentSource

(

)

const

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Returns the current media source.

See also:

setCurrentSource

void setCurrentSource

(

const MediaSource &

source

)

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Set the media source the MediaObject should use.

Parameters:

source

The MediaSource object to the media data. You can just as well use a QUrl or QString (for a local file) here. Setting an empty (invalid) source, will stop and remove the current source.

 QUrl url("http://www.example.com/music.ogg");
 media->setCurrentSource(url);

See also:

currentSource

QList<MediaSource> queue

(

)

const

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Returns the queued media sources.

This list does not include the current source (returned by currentSource).

void setQueue

(

const QList< MediaSource > &

sources

)

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Set the MediaSources to play when the current media has finished.

This function will overwrite the current queue.

See also:

clearQueue

enqueue

void setQueue

(

const QList< QUrl > &

urls

)

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Set the MediaSources to play when the current media has finished.

This function overwrites the current queue.

See also:

clearQueue

enqueue

void enqueue

(

const MediaSource &

source

)

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Appends one source to the queue.

Use this function to provide the next source just in time after the aboutToFinish signal was emitted.

See also:

aboutToFinish

setQueue

clearQueue

void enqueue

(

const QList< MediaSource > &

sources

)

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Appends multiple sources to the queue.

See also:

setQueue

clearQueue

void enqueue

(

const QList< QUrl > &

urls

)

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Appends multiple sources to the queue.

See also:

setQueue

clearQueue

void clearQueue

(

)

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Clears the queue of sources.

qint64 currentTime

(

)

const

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Get the current time (in milliseconds) of the file currently being played.

Returns:

The current time in milliseconds.

See also:

tick

qint64 totalTime

(

)

const

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Get the total time (in milliseconds) of the file currently being played.

Returns:

The total time in milliseconds.

See also:

totalTimeChanged

qint64 remainingTime

(

)

const

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Get the remaining time (in milliseconds) of the file currently being played.

Returns:

The remaining time in milliseconds.

qint32 prefinishMark

(

)

const

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void setPrefinishMark

(

qint32

msecToEnd

)

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qint32 transitionTime

(

)

const

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void setTransitionTime

(

qint32

msec

)

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void setTickInterval

(

qint32

newTickInterval

)

[slot]

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void play

(

)

[slot]

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Requests playback of the media data to start.

Playback only starts when stateChanged() signals that it goes into PlayingState, though.

Possible states right after this call:

• BufferingState
• PlayingState
• ErrorState

void pause

(

)

[slot]

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Requests playback to pause.

If it was paused before nothing changes.

Possible states right after this call:

• PlayingState
• PausedState
• ErrorState

void stop

(

)

[slot]

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Requests playback to stop.

If it was stopped before nothing changes.

Possible states right after this call:

• the state it was in before (e.g. PlayingState)
• StoppedState
• ErrorState

void seek

(

qint64

time

)

[slot]

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Requests a seek to the time indicated.

You can only seek if state() == PlayingState, BufferingState or PausedState.

The call is asynchronous, so currentTime can still be the old value right after this method was called. If all you need is a slider that shows the current position and allows the user to seek use the class SeekSlider.

Parameters:

time	The time in milliseconds where to continue playing.

Possible states right after this call:

• BufferingState
• PlayingState
• ErrorState

See also:

SeekSlider

void clear

(

)

[slot]

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Stops and removes all playing and enqueued media sources.

See also:

setCurrentSource

void stateChanged	(	Phonon::State	newstate,
		Phonon::State	oldstate
	)		[signal]

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Emitted when the state of the MediaObject has changed.

Parameters:

newstate	The state the Player is in now.
oldstate	The state the Player was in before.

void tick

(

qint64

time

)

[signal]

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This signal gets emitted every tickInterval milliseconds.

Parameters:

time	The position of the media file in milliseconds.

See also:

setTickInterval, tickInterval

void metaDataChanged

(

)

[signal]

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This signal is emitted whenever the audio/video data that is being played is associated with new meta data.

E.g. for radio streams this happens when the next song is played.

You can get the new meta data with the metaData methods.

void seekableChanged

(

bool

isSeekable

)

[signal]

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Emitted whenever the return value of isSeekable() changes.

Normally you'll check isSeekable() first and then let this signal tell you whether seeking is possible now or not. That way you don't have to poll isSeekable().

Parameters:

isSeekable

true if the stream is seekable (i.e. calling seek() works) false if the stream is not seekable (i.e. all calls to seek() will be ignored)

void hasVideoChanged

(

bool

hasVideo

)

[signal]

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Emitted whenever the return value of hasVideo() changes.

Normally you'll check hasVideo() first and then let this signal tell you whether video is available now or not. That way you don't have to poll hasVideo().

Parameters:

hasVideo

true The stream contains video and adding a VideoWidget will show a video. false There is no video data in the stream and adding a VideoWidget will show an empty (black) VideoWidget.

void bufferStatus

(

int

percentFilled

)

[signal]

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Tells about the status of the buffer.

You can use this signal to show a progress bar to the user when in BufferingState:

 progressBar->setRange(0, 100); // this is the default
 connect(media, SIGNAL(bufferStatus(int)), progressBar, SLOT(setValue(int)));

Parameters:

percentFilled

A number between 0 and 100 telling you how much the buffer is filled.

void finished

(

)

[signal]

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Emitted when the object has finished playback.

It is not emitted if you call stop(), pause() or load(), but only on end-of-queue or a critical error.

Warning:

This signal is not emitted when the current source has finished and there's another source in the queue. It is only emitted when the queue is empty.

See also:

currentSourceChanged

aboutToFinish

prefinishMarkReached

void currentSourceChanged

(

const Phonon::MediaSource &

newSource

)

[signal]

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Emitted when the MediaObject makes a transition to the next MediaSource in the queue().

In other words, it is emitted when an individual MediaSource is finished.

Parameters:

newSource

The source that starts to play at the time the signal is emitted.

void aboutToFinish

(

)

[signal]

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Emitted before the playback of the whole queue stops.

When this signal is emitted you still have time to provide the next MediaSource (using enqueue()) so that playback continues.

This signal can be used to provide the next MediaSource just in time for the transition still to work.

See also:

enqueue

void prefinishMarkReached

(

qint32

msecToEnd

)

[signal]

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Emitted when there are only msecToEnd milliseconds left for playback.

Parameters:

msecToEnd

The remaining time until the playback queue finishes.

Warning:

This signal is not emitted when there is another source in the queue. It is only emitted when the queue is empty.

See also:

setPrefinishMark

prefinishMark

aboutToFinish

finished

void totalTimeChanged

(

qint64

newTotalTime

)

[signal]

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This signal is emitted as soon as the total time of the media file is known or has changed.

For most non-local media data the total time of the media can only be known after some time. Initially the totalTime function can not return useful information. You have to wait for this signal to know the real total time.

Parameters:

newTotalTime

The length of the media file in milliseconds.

See also:

totalTime

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Friends And Related Function Documentation

friend class FrontendInterfacePrivate [friend]

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Definition at line 87 of file mediaobject.h.

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Property Documentation

qint32 transitionTime [read, write]

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Defines the time between media sources.

A positive transition time defines a gap of silence between queued media sources.

A transition time of 0 ms requests gapless playback (sample precise queueing of the next source).

A negative transition time defines a crossfade between the queued media sources.

Defaults to 0 (gapless playback).

Warning:

This feature might not work reliably on every platform.

Definition at line 107 of file mediaobject.h.

qint32 prefinishMark [read, write]

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Get a signal before playback finishes.

This property specifies the time in milliseconds the prefinishMarkReached signal is emitted before the playback finishes. A value of 0 disables the signal.

Defaults to 0 (disabled).

Warning:

For some media data the total time cannot be determined accurately, therefore the accuracy of the prefinishMarkReached signal can be bad sometimes. Still, it is better to use this method than to look at totalTime() and currentTime() to emulate the behaviour because the backend might have more information available than your application does through totalTime and currentTime.

See also:

prefinishMarkReached

Definition at line 128 of file mediaobject.h.

qint32 tickInterval [read, write]

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The time interval in milliseconds between two ticks.

The tick interval is the time that elapses between the emission of two tick signals. If you set the interval to 0 the tick signal gets disabled.

Defaults to 0 (disabled).

Warning:

The back-end is free to choose a different tick interval close to what you asked for. This means that the following code may fail:

 int x = 200;
 media->setTickInterval(x);
 Q_ASSERT(x == producer->tickInterval());

On the other hand the following is guaranteed:

 int x = 200;
 media->setTickInterval(x);
 Q_ASSERT(x >= producer->tickInterval() &&
          x <= 2 * producer->tickInterval());

See also:

tick

Definition at line 155 of file mediaobject.h.

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The documentation for this class was generated from the following file:

• phonon/mediaobject.h