- Qt 6.8
- Qt Multimedia
- Qt Multimedia Examples
- QML Video Recorder
- Qt 6.8.0 Reference Documentation

# QML Video Recorder

Recording audio and video using Qt Quick.

QML Recorder demonstrates a simple application that can record audio and video separate or together, using a microphone, a camera, or with screen capturing.

#### 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.

#### Overview

At its core, this is a QML application, see Getting Started Programming with Qt Quick. This documentation is focused on how this example uses the Qt Multimedia QML Types.

The example uses the QML Camera and AudioInput types connected to a CaptureSession. A MediaRecorder object is then used to record the captured audio and video.

In addition to QtMultimedia, features of Qt Quick Windows, Controls, and Layouts are used to implement the graphic user interface and functionality. Playback won't be covered here, for that see the QML Media Player Example.

The example demonstrates the following:

- Input devices can be selected.
- An input type switched off.
- Settings for capturing such as quality, codec choice, file format, and assigning metadata.
- Captured files are stored and can be played back.

#### Recording

The application implements recording.

##### captureSession

In `main.qml`, `captureSession` is declared like so:

         CaptureSession {
             id: captureSession
             recorder: recorder
             audioInput: controls.audioInput
             camera: controls.camera
             screenCapture: controls.screenCapture
             windowCapture: controls.windowCapture
             videoOutput: videoOutput
         }

##### recorder

In `main.qml`, the MediaRecorder `recorder` handles recording media as well as capturing a thumbnail for the file and appending it to a ListModel, `mediaList`.

         MediaRecorder {
             id: recorder
             onRecorderStateChanged:
                 (state) => {
                     if (state === MediaRecorder.StoppedState) {
                         root.contentOrientation = Qt.PrimaryOrientation
                         mediaList.append()
                     } else if (state === MediaRecorder.RecordingState && captureSession.camera) {
                         // lock orientation while recording and create a preview image
                         root.contentOrientation = root.screen.orientation;
                         videoOutput.grabToImage(function(res) { mediaList.mediaThumbnail = res.url })
                     }
                 }
             onActualLocationChanged: (url) => { mediaList.mediaUrl = url }
             onErrorOccurred: { recorderErrorText.text = recorder.errorString; recorderError.open(); }
         }

`mediaList` is declared in the Frame `mediaListFrame`

         Frame {
             id: mediaListFrame
             height: 150
             width: parent.width
             anchors.bottom: controlsFrame.top
             x: controls.capturesVisible ? 0 : parent.width
             background: Rectangle {
                 anchors.fill: parent
                 color: palette.base
                 opacity: 0.8
             }

             Behavior on x { NumberAnimation { duration: 200 } }

             MediaList {
                 id: mediaList
                 anchors.fill: parent
                 playback: playback

##### controls

These are defined in `Controls.qml` and declared in main.qml.

Its root is a Row that contains the Columns `inputControls`, `recordButton`, `optionButtons`, each defined in their own .qml files.

###### Selecting a video source

Defined in `VideoSourceSelect.qml`, `VideoSourceSlect` is comprised of a Switch and a ComboBox and enables the user to select from available cameras.

     Row {
         id: root
         height: Style.height
         property Camera selectedCamera: cameraAvailable ? camera : null
         property ScreenCapture selectedScreenCapture: screenAvailable ? screenCapture : null
         property WindowCapture selectedWindowCapture: windowAvailable ? windowCapture : null

         property bool sourceAvailable: typeof comboBox.currentValue !== 'undefined' &&
                                        comboBox.currentValue.type !== 'toggler' &&
                                        videoSourceSwitch.checked

         property bool cameraAvailable: sourceAvailable && comboBox.currentValue.type === 'camera'
         property bool screenAvailable: sourceAvailable && comboBox.currentValue.type === 'screen'
         property bool windowAvailable: sourceAvailable && comboBox.currentValue.type === 'window'

         Component.onCompleted: {
             videoSourceModel.populate()

             for (var i = 0; i < videoSourceModel.count; i++) {
                 if (videoSourceModel.get(i).value.type !== 'toggler') {
                     comboBox.currentIndex = i
                     break
                 }
             }
         }

         Camera {
             id: camera
             active: cameraAvailable
         }

         ScreenCapture {
             id: screenCapture
             active: screenAvailable
         }

         WindowCapture {
             id: windowCapture
             active: windowAvailable
         }

         MediaDevices { id: mediaDevices
             onVideoInputsChanged: {

                 videoSourceModel.populate()

                 for (var i = 0; i < videoSourceModel.count; i++) {
                     if (videoSourceModel.get(i).value.type !== 'toggler') {
                         comboBox.currentIndex = i
                         break
                     }
                 }
             }
         }

         Switch {
             id: videoSourceSwitch
             anchors.verticalCenter: parent.verticalCenter
             checked: true
         }

         ListModel {
             id: videoSourceModel
             property var enabledSources: {
                 'camera': true,
                 'screen': true,
                 'window': false
             }

             function toggleEnabledSource(type) {
                 enabledSources[type] = !enabledSources[type]
                 populate()
             }

             function appendItem(text, value) {
                 append({ text: text, value: value})
             }

             function appendToggler(name, sourceType) {
                 appendItem((enabledSources[sourceType] ? "- Hide " : "+ Show ") + name,
                            { type: 'toggler', 'sourceType': sourceType })
             }

             function populate() {
                 clear()

                 appendToggler('Cameras', 'camera')
                 if (enabledSources['camera'])
                     for (var camera of mediaDevices.videoInputs)
                         appendItem(camera.description, { type: 'camera', camera: camera })

                 appendToggler('Screens', 'screen')
                 if (enabledSources['screen'])
                     for (var screen of Application.screens)
                         appendItem(screen.name, { type: 'screen', screen: screen })

                 appendToggler('Windows', 'window')
                 if (enabledSources['window'])
                     for (var window of windowCapture.capturableWindows())
                         appendItem(window.description, { type: 'window', window: window })
             }
         }

`comboBox`, declared in the above snippet, assigns the current video source.

         ComboBox {
             id: comboBox
             width: Style.widthLong
             height: Style.height
             background: StyleRectangle { anchors.fill: parent }
             model: videoSourceModel
             displayText: typeof currentValue === 'undefined' ||
                          currentValue.type === 'toggler' ? "Unavailable" : currentText
             font.pointSize: Style.fontSize
             textRole: "text"
             valueRole: "value"
             onCurrentValueChanged: {
                 if (typeof currentValue === 'undefined')
                     return
                 if (currentValue.type === 'screen')
                     screenCapture.screen = currentValue.screen
                 else if (currentValue.type === 'camera')
                     camera.cameraDevice = currentValue.camera

###### Selecting an audio input

Implemented in the same way as Selecting a video source and defined in `AudioInputSelect.qml` like so:

     Row {
         id: root
         height: Style.height
         property AudioInput selected: available ? audioInput : null
         property bool available: (typeof comboBox.currentValue !== 'undefined') && audioSwitch.checked

         Component.onCompleted: {
             audioInputModel.populate()
             comboBox.currentIndex = 0
         }

         MediaDevices { id: mediaDevices }

         AudioInput { id: audioInput; muted: !audioSwitch.checked }

         Switch {
             id: audioSwitch;
             height: Style.height;
             checked: true
         }

         ListModel {
             id: audioInputModel
             property var audioInputs: mediaDevices.audioInputs

             function populate() {
                 audioInputModel.clear()

                 for (var audioDevice of audioInputs)
                     audioInputModel.append({ text: audioDevice.description, value:
                                             { type: 'audioDevice', audioDevice: audioDevice } })
             }
         }
         ComboBox {
             id: comboBox
             width: Style.widthLong
             height: Style.height
             background: StyleRectangle { anchors.fill: parent }
             model: audioInputModel
             textRole: "text"
             font.pointSize: Style.fontSize
             displayText: typeof currentValue === 'undefined' ? "unavailable" : currentText
             valueRole: "value"

Example project @ code.qt.io