The Multimedia API in the Mobility Project gives developers a simplified way to use audio and video playback. The Multimedia QML Plugin provides a QML friendly interface to these features.
The audio element is an easy way to add audio playback to a Qt Quick scene. Mobility provides properties for control, methods (functions) and signals.
The code extract below shows the creation and use of an audio element.
import Qt 4.7 import QtMultimediaKit 1.1 ... Audio { id: playMusic source: "music.wav" } MouseArea { id: playArea anchors.fill: parent onPressed: { playMusic.play() } }
The snippet above shows how the inclusion of playMusic enables audio features on the element that contains it. So that when the parent's MouseArea is clicked the play() method of the audio element is run. Other typical audio control methods are available such as pause() and stop().
Much of the getting / setting of audio parameters is done through properties. These include
Property | Description |
---|---|
The source URL of the media. | |
Indicates if loading of media should begin immediately. | |
Indicates that the media is playing. | |
The media is paused. | |
The status of media loading. | |
Amount of time in milliseconds the media will play. | |
Current position in the media in milliseconds of play. | |
Audio output volume: from 0.0 (silent) to 1.0 (maximum) | |
Indicates audio is muted. | |
Indicates how full the data buffer is: 0.0 (empty) to 1.0 (full). | |
Indicates whether the audio position can be changed. | |
The rate at which audio is played at as a multiple of the normal rate. | |
An error code for the error state including NoError | |
A description of the current error condition. |
The set of signals available allow the developer to create custom behavior when the following events occur,
Signal | Description |
---|---|
Called when playback has been started. | |
Called when playback is resumed from the paused state. | |
Called when playback is paused. | |
Called when playback is stopped. | |
Called when the specified error occurs. |
Adding video playback, with sound, to a Qt Quick scene is also easy. The process is very similar to that of Audio above, in fact Video shares many of the property names, methods and signals. Here is the equivalent sample code to implement a video playback element in a scene
Video { id: video width : 800 height : 600 source: "video.avi" MouseArea { anchors.fill: parent onClicked: { video.play() } } focus: true Keys.onSpacePressed: video.paused = !video.paused Keys.onLeftPressed: video.position -= 5000 Keys.onRightPressed: video.position += 5000 }
There are similar features like play() with new features specific to video.
In the above sample when the parent of MouseArea is clicked, an area of 800x600 pixels with an id of 'video', the source "video.avi" will play in that area. Notice also that signals for the Keys element have been defined so that a spacebar will toggle the pause button; the left arrow will move the current position in the video to 5 seconds previously; and the right arrow will advance the current position in the video by 5 seconds.
Most of the differences will obviously be about video control and information. There are many properties associated with the Video element, most of them deal with meta-data, control of the video media and aspects of presentation.
Note: This element is currently not supported on Symbian platforms.