- Qt 6.8
- Qt Multimedia
- Qt Multimedia Examples
- QML Media Player Example
- Qt 6.8.2 Reference Documentation

# QML Media Player Example

Playing audio and video using the QML `MediaPlayer` type.

This example demonstrates a simple multimedia player that can play audio and video files using various codecs.

#### Running the Example

To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.

#### Instantiating the MediaPlayer

The entry point for the QML code in this example is `Main.qml`. Here an `ApplicationWindow` is created and properties such as the `id`, `title`, `width` and `height` are set.

     ApplicationWindow {
         id: root
         title: qsTr("Multimedia Player")
         width: 1280
         height: 720

Next the `MediaPlayer` is created and the two properties that are responsible for the video and audio output are defined. Firstly, `videoOutput` which renders the video viewfinder and secondly `audioOutput` which provides the audio output for the player.

     MediaPlayer {
         id: mediaPlayer
         ...
     videoOutput: videoOutput
     audioOutput: AudioOutput {
         id: audio
         muted: playbackController.muted
         volume: playbackController.volume
     }
         ...
     VideoOutput {
         id: videoOutput
         anchors.fill: parent
         visible: mediaPlayer.mediaStatus > 0

         TapHandler {
             onDoubleTapped: {
                 root.fullScreen ?  root.showNormal() : root.showFullScreen()
                 root.fullScreen = !root.fullScreen
             }
         }
     }

The `visible` property of the `VideoOutput` type is set to `true` when the `mediaStatus` property of the `MediaPlayer` is greater than 0. `mediaStatus` is of enumeration type and is equal to 0 when No media has been set, and greater than 0 otherwise. Therefore, the `VideoOutput` is visible when media has been set.

The `MediaPlayer` type has a signal property called `onErrorOccurred` that can be overridden specifically to handle errors. In this case the signal opens a `MessageDialog` using the method `open()` and sets its `text` property to a `MediaPlayer` property called `errorString`.

     onErrorOccurred: {
         mediaError.text = mediaPlayer.errorString
         mediaError.open()
     }

#### Playback Controls

In order to have a useable media player, there needs to be an interface to control the playback. This is created in its own component file, `PlaybackControl.qml`, and instantiated in `Main.qml`.

     PlaybackControl {
         id: playbackController
         ...
     onTracksChanged: {
         audioTracksInfo.read(mediaPlayer.audioTracks)
         videoTracksInfo.read(mediaPlayer.videoTracks)
         subtitleTracksInfo.read(mediaPlayer.subtitleTracks, 6) /* QMediaMetaData::Language = 6 */
         updateMetadata()
         mediaPlayer.play()
     }

When created, objects are forwarded to this type such as track information, metadata information and the `MediaPlayer` object itself. In `PlaybackControl.qml`, each one of these objects have a `required property`, meaning that these properties must be set when the `PlaybackControl` object is created.

     Item {
         id: playbackController

         required property MediaPlayer mediaPlayer
         required property MetadataInfo metadataInfo
         required property TracksInfo audioTracksInfo
         required property TracksInfo videoTracksInfo
         required property TracksInfo subtitleTracksInfo

These playback controls can be broken down into sections. In the top left of the panel lies a collection of buttons used to open a file, either by selecting a file from a file explorer or entering a URL. The file is loaded into the `MediaPlayer` by setting the `source` property. Both buttons are instantiated using a `CustomButton` `custom component`.

     CustomButton {
         id: fileDialogButton
         icon.source: "../images/open_new.svg"
         flat: false
         onClicked: fileDialog.open()
     }

     CustomButton {
         id: openUrlButton
         icon.source: "../images/link.svg"
         flat: false
         onClicked: urlPopup.open()
     }

Three buttons are created and centered on this panel, handling play, pause and seeking ten seconds backwards or forwards. The media is played and paused using the methods `play()` and `pause()`, respectively. To know when to draw a play or pause button, the `playbackState` property is queried. For example, when it is equal to the enum value `MediaPlayer.PlayingState` then the pause button is drawn.

     CustomRoundButton {
         id: playButton
         visible: playbackController.mediaPlayer.playbackState !== MediaPlayer.PlayingState
         icon.source: "../images/play_symbol.svg"
         onClicked: playbackController.mediaPlayer.play()
     }

     CustomRoundButton {
         id: pauseButton
         visible: playbackController.mediaPlayer.playbackState === MediaPlayer.PlayingState
         icon.source: "../images/pause_symbol.svg"
         onClicked: playbackController.mediaPlayer.pause()
     }

To navigate ten seconds forward or backwards, the `position` of the `MediaPlayer` type is incremented by 10,000 milliseconds and set using the method `setPosition()`.

     CustomRoundButton {
         id: forward10Button
         icon.source: "../images/forward10.svg"
         onClicked: {
             const pos = Math.min(playbackController.mediaPlayer.duration,
                                playbackController.mediaPlayer.position + 10000)
             playbackController.mediaPlayer.setPosition(pos)
         }
     }

#### Playback Seeking and Audio

In `PlaybackControl.qml`, an `AudioControl` and a `PlaybackSeekControl` type are instantiated. These are both defined in their own component file and are responsible for volume control and playback seeking, respectively. The `AudioControl` type defines a button to mute and a `Slider`, from `QtQuick Controls`, to set the volume of the player. Both of these attributes are exposed by defining a `mute` and `volume` property and are accessed from the `AudioOutput` definition in `Main.qml`.

     property alias muted: muteButton.checked
     property real volume: slider.value

The `PlaybackSeekControl` uses a `RowLayout` containing a `Slider` with a `Text` item either side. The two `Text` items display the current time and the remaining time of the media being played. These are both calculated using two properties of the `MediaPlayer` type, `position`, which gives the current playback position in milliseconds, and `duration`, which gives the duration of the media in milliseconds.

     Text {
         id: currentTime
         Layout.preferredWidth: 45
         text: seekController.formatToMinutes(seekController.mediaPlayer.position)
         horizontalAlignment: Text.AlignLeft
         font.pixelSize: 11
     }
         ...
     Text {
         id: remainingTime
         Layout.preferredWidth: 45
         text: seekController.formatToMinutes(seekController.mediaPlayer.duration - seekController.mediaPlayer.position)
         horizontalAlignment: Text.AlignRight
         font.pixelSize: 11
     }

The `Slider` is only enabled when the media player is seekable and not, for example, live media. The `MediaPlayer` type has a property for this called `seekable`. The `value` of the `Slider` is calculated using the `position` and `duration` properties of the `MediaPlayer`.

     enabled: seekController.mediaPlayer.seekable
     value: seekController.mediaPlayer.position / seekController.mediaPlayer.duration

#### Metadata and Track Information

The `PlaybackControl` type instantiates a `SettingsPopup`, which contains information about the metadata of the currently loaded media and track selection, as well as the ability to update the playback rate. This `Popup` is defined in `SettingsPopup.qml`.

The metadata is contained in its own component file, `MetadataInfo.qml`. It contains a `ListModel`, a function to clear it, `clear()`, and a function to populate it, `read(MediaMetadata metadata)`. The `read(MediaMetadata metadata)` function takes as a parameter an object of type `MediaMetaData`, and navigates its key-value structure to extract its data into the `model` of the `ListView`. The methods used to do this are `keys()`, which returns all the keys of the `MediaMetaData`, and {stringValue(Key key)}, which returns the `value` for a given `key`.

     function read(metadata) {
         if (!metadata)
             return
         for (const key of metadata.keys())
             if (metadata.stringValue(key))
                 listModel.append({
                                     name: metadata.metaDataKeyToString(key),
                                     value: metadata.stringValue(key)
                                 })
     }

     ListModel {
         id: listModel
     }

The data is then displayed in `SettingsPopup.qml` in a `ListView` type. The `delegate` of this `ListView` is a row of two `Text` items, corresponding to the key-value pairs abstracted from the `MediaMetaData` item.

On the other side of the `Popup` there is playback rate controls and track selection for audio, video and subtitles. The playback rate is chosen from a `ComboBox` and set using the property `playbackRate`.

     settingsController.mediaPlayer.playbackRate = (currentIndex + 1) * 0.25

The type called `TracksInfo`, defined in `TracksInfo.qml`, contains the data about the tracks. More specifically, a `ListModel` containing the titles of the tracks, or for subtitles specifically, the langauges. This information is populated in `Main.qml` by calling the `read(MediaMetadata mediaMetadata)` function defined in the `TracksInfo` type.

     onTracksChanged: {
         audioTracksInfo.read(mediaPlayer.audioTracks)
         videoTracksInfo.read(mediaPlayer.videoTracks)
         subtitleTracksInfo.read(mediaPlayer.subtitleTracks, 6) /* QMediaMetaData::Language = 6 */
         updateMetadata()
         mediaPlayer.play()
     }

The `model` defined in `TracksInfo` is then queried in the `ComboBox`es in the `SettingsPopup` to select the current track.

     settingsController.mediaPlayer.pause()
     tracksInfo.selectedTrack = currentIndex
     settingsController.mediaPlayer.play()

Example project @ code.qt.io