Qt Multimedia QML API | Qt Multimedia 5.9

Qt 5.9 | Qt Multimedia | Qt Multimedia QML API

Qt 5.9.3 Reference Documentation

# Qt Multimedia QML API

## Overview

The Qt Multimedia module gives developers a simplified way to use audio and video playback, and access camera functionality. The Multimedia QML API provides a QML friendly interface to these features.

## Types

### Audio

Audio is an easy way to add audio playback to a Qt Quick scene. Qt Multimedia provides properties for control, methods (functions) and signals.

The code extract below shows the creation and use of an Audio instance.

      Item {
          width: 640
          height: 360

          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 type that contains it. So that when the parent's MouseArea is clicked the play() method of Audio 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
--- | ---
source | The source URL of the media.
autoLoad | Indicates if loading of media should begin immediately.
playing | Indicates that the media is playing.
paused | The media is paused.
status | The status of media loading.
duration | Amount of time in milliseconds the media will play.
position | Current position in the media in milliseconds of play.
volume | Audio output volume: from 0.0 (silent) to 1.0 (maximum)
muted | Indicates audio is muted.
bufferProgress | Indicates how full the data buffer is: 0.0 (empty) to 1.0 (full).
seekable | Indicates whether the audio position can be changed.
playbackRate | The rate at which audio is played at as a multiple of the normal rate.
error | An error code for the error state including NoError
errorString | 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
--- | ---
playing | Called when playback is started, or when resumed from paused state.
paused | Called when playback is paused.
stopped | Called when playback is stopped.
error | Called when the specified error occurs.

### Camera

Camera enables still image and video capture using QML. It has a number of properties that help setting it up.

The details of using a Camera are described in further depth in the Camera Overview and in the corresponding reference documentation.

### Video

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 video playback 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 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 Video, most of them deal with meta-data, control of the video media and aspects of presentation.

### SoundEffect

SoundEffect provides a way to play short sound effects, like in video games. Multiple sound effect instances can be played simultaneously. You should use Audio for music playback.

      Item {
          width: 640
          height: 360

          SoundEffect {
              id: effect
              source: "test.wav"
          }
          MouseArea {
              id: playArea
              anchors.fill: parent
              onPressed:  { effect.play() }
          }
      }

In the above sample the sound effect will be played when the MouseArea is clicked.

For a complete description of this type, see SoundEffect

## Multimedia QML Types

Video | A convenience type for showing a specified video
Audio | Add audio playback to a scene
MediaPlayer | Add media playback to a scene
Camera | Access viewfinder frames, and take photos and movies
CameraCapture | An interface for capturing camera images
CameraExposure | An interface for exposure related camera settings
CameraFlash | An interface for flash related camera settings
CameraFocus | An interface for focus related camera settings
CameraImageProcessing | An interface for camera capture related settings
CameraRecorder | Controls video recording with the Camera
QtMultimedia | Provides a global object with useful functions from Qt Multimedia
Playlist | For specifying a list of media to be played
PlaylistItem | Defines an item in a Playlist
Radio | Access radio functionality from a QML application
RadioData | Access RDS data from a QML application
Torch | Simple control over torch functionality
SoundEffect | Type provides a way to play sound effects in QML
VideoOutput | Render video or camera viewfinder