使用 Qt Quick 播放音频和视频。
This example demonstrates a simple multimedia player that can play audio and video files using various codecs.
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At its core this is a QML application, see 采用 Qt Quick 快速入门编程 for information specific to that. This documentation is focused on how this example utilizes the Qt Multimedia QML types .
在
main.qml
a
MediaPlayer
instance is connected to a
VideoOutput
to play back the video:
MediaPlayer {
id: mediaPlayer
function updateMetadata() {
metadataInfo.clear();
metadataInfo.read(mediaPlayer.metaData);
metadataInfo.read(mediaPlayer.audioTracks[mediaPlayer.activeAudioTrack]);
metadataInfo.read(mediaPlayer.videoTracks[mediaPlayer.activeVideoTrack]);
}
videoOutput: videoOutput
videoOutput
is declared like so:
VideoOutput {
id: videoOutput
property bool fullScreen: false
anchors.top: fullScreen ? parent.top : menuBar.bottom
anchors.bottom: playbackControl.top
anchors.left: parent.left
anchors.right: parent.right
TapHandler {
onDoubleTapped: {
parent.fullScreen ? showNormal() : showFullScreen()
parent.fullScreen = !parent.fullScreen
}
onTapped: {
metadataInfo.visible = false
audioTracksInfo.visible = false
videoTracksInfo.visible = false
subtitleTracksInfo.visible = false
}
}
}
This QML type handles media selection from a url or local file, exiting the application, viewing meta data, and the selection of available video, audio or subtitle tracks.
Accessing the mediaPlayer object is done through properties:
required property MediaPlayer mediaPlayer
required property VideoOutput videoOutput
required property MetadataInfo metadataInfo
required property TracksInfo audioTracksInfo
required property TracksInfo videoTracksInfo
required property TracksInfo subtitleTracksInfo
A FileDialog,
fileDialog
, is created with an
onAccepted
function that will stop
mediaPlayer
, load the source by setting the
source
property and then play it automatically:
FileDialog {
id: fileDialog
title: "Please choose a file"
onAccepted: {
mediaPlayer.stop()
mediaPlayer.source = fileDialog.currentFile
mediaPlayer.play()
}
}
This is triggered in the Menu
File
, which is a child of the
MenuBar
:
MenuBar {
id: menuBar
anchors.left: parent.left
anchors.right: parent.right
Menu {
title: qsTr("&File")
Action {
text: qsTr("&Open")
onTriggered: fileDialog.open()
While
urlPopup
handles prompting and capturing a url, it is the
loadUrl
function that interacts with
mediaPlayer
像这样：
function loadUrl(url) {
mediaPlayer.stop()
mediaPlayer.source = url
mediaPlayer.play()
}
In the declaration of
mediaPlayer
, in
main.qml
, there is the function
updateMetadata()
:
function updateMetadata() {
metadataInfo.clear();
metadataInfo.read(mediaPlayer.metaData);
metadataInfo.read(mediaPlayer.audioTracks[mediaPlayer.activeAudioTrack]);
metadataInfo.read(mediaPlayer.videoTracks[mediaPlayer.activeVideoTrack]);
It is called in the following places:
onMetaDataChanged: { updateMetadata() }
onTracksChanged: {
audioTracksInfo.read(mediaPlayer.audioTracks);
audioTracksInfo.selectedTrack = mediaPlayer.activeAudioTrack;
videoTracksInfo.read(mediaPlayer.videoTracks);
videoTracksInfo.selectedTrack = mediaPlayer.activeVideoTrack;
subtitleTracksInfo.read(mediaPlayer.subtitleTracks);
subtitleTracksInfo.selectedTrack = mediaPlayer.activeSubtitleTrack;
updateMetadata()
}
Reading MetaData is done by the
MetadataInfo
type's
read()
function
function read(metadata) {
if (metadata) {
for (var key of metadata.keys()) {
if (metadata.stringValue(key)) {
elements.append(
{ name: metadata.metaDataKeyToString(key)
, value: metadata.stringValue(key)
})
}
}
}
}
The information is displayed via an Overlay 项。
This is defined in
TracksInfo.qml
and reading available tracks is done in a similar way to
MetadataInfo
:
function read(metadataList) {
var LanguageKey = 6;
elements.clear()
elements.append(
{ language: "No Selected Track"
, trackNumber: -1
})
if (!metadataList)
return;
metadataList.forEach(function (metadata, index) {
var language = metadata.stringValue(LanguageKey);
var label = language ? metadata.stringValue(LanguageKey) : "track " + (index + 1)
elements.append(
{ language: label
, trackNumber: index
})
});
}
To set a track, the property
selectedTrack
is set like so:
ListView {
id: trackList
visible: elements.count > 0
anchors.fill: parent
model: elements
delegate: RowLayout {
width: trackList.width
RadioButton {
checked: model.trackNumber === selectedTrack
text: model.language
ButtonGroup.group: group
onClicked: selectedTrack = model.trackNumber
}
}
}
The
onSelectectedTrackChanged
signal, in each relevant
TracksInfo
instance in
main.qml
, is what makes changes to
mediaPlayer
像这样：
id: audioTracksInfo
anchors.right: parent.right
anchors.top: videoOutput.fullScreen ? parent.top : menuBar.bottom
anchors.bottom: playbackControl.opacity ? playbackControl.bottom : parent.bottom
visible: false
onSelectedTrackChanged: mediaPlayer.activeAudioTrack = audioTracksInfo.selectedTrack
This item has controls for Playback control , Play Pause Stop , Playback rate control and Playback seek control .
This qml type handles media playback and interacts with the
MediaPlayer
in
main.qml
.
Here are the property definitions.
required property MediaPlayer mediaPlayer
property int mediaPlayerState: mediaPlayer.playbackState
Connections:
target: mediaPlayer
function onPlaybackStateChanged() { updateOpacity() }
function onHasVideoChanged() { updateOpacity() }
}
Play , stop and pause interactions with the MediaPlayer object are done like so:
RoundButton {
id: pauseButton
radius: 50.0
text: "\u2016";
onClicked: mediaPlayer.pause()
}
RoundButton {
id: playButton
radius: 50.0
text: "\u25B6";
onClicked: mediaPlayer.play()
}
RoundButton {
id: stopButton
radius: 50.0
text: "\u25A0";
onClicked: mediaPlayer.stop()
}
}
Playback states done using playbackstate 像这样：
State {
name: "playing"
when: mediaPlayerState == MediaPlayer.PlayingState
PropertyChanges { target: pauseButton; visible: true}
PropertyChanges { target: playButton; visible: false}
PropertyChanges { target: stopButton; visible: true}
},
State {
name: "stopped"
when: mediaPlayerState == MediaPlayer.StoppedState
PropertyChanges { target: pauseButton; visible: false}
PropertyChanges { target: playButton; visible: true}
PropertyChanges { target: stopButton; visible: false}
},
State {
name: "paused"
when: mediaPlayerState == MediaPlayer.PausedState
PropertyChanges { target: pauseButton; visible: false}
PropertyChanges { target: playButton; visible: true}
PropertyChanges { target: stopButton; visible: true}
}
]
Defined in
PlaybackSeekControl.qml
, this component comprises of an item with a Text,
mediaTime
，和
Slider
,
mediaSlider
, in a
RowLayout
.
mediaTime
使用
MediaPlayer
's
position
property like so:
Text {
id: mediaTime
Layout.minimumWidth: 50
Layout.minimumHeight: 18
horizontalAlignment: Text.AlignRight
text: {
var m = Math.floor(mediaPlayer.position / 60000)
var ms = (mediaPlayer.position / 1000 - m * 60).toFixed(1)
return `${m}:${ms.padStart(4, 0)}`
}
}
mediaSlider
使用
MediaPlayer
seekable
,
duration
，和
position
properties like so:
Slider {
id: mediaSlider
Layout.fillWidth: true
enabled: mediaPlayer.seekable
to: 1.0
value: mediaPlayer.position / mediaPlayer.duration
onMoved: mediaPlayer.setPosition(value * mediaPlayer.duration)
}
This type is defined in
PlaybackRateControl.qml
像这样：
Slider {
id: slider
Layout.fillWidth: true
snapMode: Slider.SnapOnRelease
enabled: true
from: 0.5
to: 2.5
stepSize: 0.5
value: 1.0
onMoved: { mediaPlayer.setPlaybackRate(value) }
}
Text {
text: "Rate " + slider.value + "x"
This type is defined in
AudioControl.qml
, and utilizes the
muted
and
volume
properties of the
AudioOutput
instantiated within the
MediaPlayer
, which is instantiated in
main.qml
.
required property MediaPlayer mediaPlayer
property bool muted: false
property real volume: volumeSlider.value/100.
implicitHeight: buttons.height
RowLayout {
anchors.fill: parent
Item {
id: buttons
width: muteButton.implicitWidth
height: muteButton.implicitHeight
RoundButton {
id: muteButton
radius: 50.0
icon.source: muted ? "qrc:///Mute_Icon.svg" : "qrc:///Speaker_Icon.svg"
onClicked: { muted = !muted }
}
}
Slider {
id: volumeSlider
Layout.fillWidth: true
Layout.alignment: Qt.AlignVCenter
enabled: true
to: 100.0
value: 100.0