Multimedia Development

How do I obtain the frame data of a camera when using the XComponent to display the preview output stream of the camera?

Applicable to: OpenHarmony 3.2 (API version 9, stage model)

Symptom

Currently, the API does not support real-time preview of the camera frame data. To obtain the frame data, you must bind an action, for example, photographing.

Solution

Create a dual-channel preview to obtain the frame data.

1. Use the XComponent to create a preview stream.

   // Obtain a PreviewOutput instance.
   const surfaceId = globalThis.mxXComponentController.getXComponentSurfaceld();
   this.mPreviewOutput = await Camera.createPreviewOutput(surfaceld) ;
   

2. Use imageReceiver to listen for image information.

   // Add dual-channel preview.
   const fullWidth = this.mFullScreenSize.width;
   const fullHeight = this.mFullScreenSize.height;
   const imageReceiver = await image.createImageReceiver(fullwidth, fullHeight, 
     formatImage, capacityImage) ;
   const photoSurfaceId = await imageReceiver.getReceivingSurfaceld();
   this.mPreviewOutputDouble = await Camera.createPreviewOutput ( photoSurfaceld)
   

How do I obtain the preview image of the front camera?

Applicable to: OpenHarmony 3.2 (API version 9, stage model)

Solution

1. Use the @ohos.multimedia.camera module to obtain the physical camera information.

   let cameraManager = await camera.getCameraManager(context);
   let camerasInfo = await cameraManager.getSupportedCameras();
   let cameraDevice = this.camerasInfo[0];
   

2. Create and start the input stream channel of the physical camera.

   let cameraInput = await cameraManager.createCameraInput(cameraDevice);
   await this.cameraInput.open();
   

3. Obtain the output formats supported by the camera, and create a preview output channel based on the surface ID provided by the XComponent.

   let outputCapability = await this.cameraManager.getSupportedOutputCapability(cameraDevice);
   let previewProfile = this.outputCapability.previewProfiles[0];
   let previewOutput = await cameraManager.createPreviewOutput(previewProfile, previewId);
   

4. Create a camera session, add the camera input stream and preview output stream to the session, and start the session. The preview image is displayed on the XComponent.

   let captureSession = await cameraManager.createCaptureSession();
   await captureSession.beginConfig();
   await captureSession.addInput(cameraInput);
   await captureSession.addOutput(previewOutput);
   await this.captureSession.commitConfig()
   await this.captureSession.start();
   

How do I set the camera focal length?

Applicable to: OpenHarmony 3.2 (API version 9, stage model)

Solution

1. Check whether the camera is a front camera. A front camera does not support focal length setting.
2. Use captureSession.getZoomRatioRange() to obtain the focal length range supported by the device.
3. Check whether the target focal length is within the range obtained. If yes, call captureSession.setZoomRatio() to set the focal length.

How do I play music in the background?

Applicable to: OpenHarmony 3.2 (API version 9, stage model)

Symptom

Music cannot be played in the background.

Solution

AVSession controls media playback. When a third-party application switches to the background or encounters a screen lock event, media playback is forcibly paused and the application is unaware of the pause. To enable the application to continue the playback in the background, request a continuous task and access the AVSession capability, which allows Control Panel to control the playback behavior of third-party applications.

Reference

Continuous Task Development

AVSession Development

What should I do when multiple video components cannot be used for playback?

Applicable to: OpenHarmony 3.2 (API version 9, stage model)

Symptom

A large number of video components are created. They cannot play media normally or even crash.

Solution

A maximum of 13 media player instances can be created.

How do I invoke the image library directly?

Applicable to: OpenHarmony 3.2 (API version 9, stage model)

Solution

let want = {
  bundleName: 'com.ohos.photos',
  abilityName: 'com.ohos.photos.MainAbility',
  parameters: {
 uri: 'detail'
  }
};
let context = getContext(this) as common.UIAbilityContext;
context.startAbility(want);