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)

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)

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)

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)

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.

References

Continuous Task

AVSession Development

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

Applicable to: OpenHarmony 3.2 (API version 9)

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)

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);

How do I apply for the media read/write permission on a device?

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

Solution

1. Configure the permissions ohos.permission.READ_MEDIA and ohos.permission.WRITE_MEDIA in the module.json5 file.

   Example:

   {
     "module" : {
       "requestPermissions":[
         {
           "name" : "ohos.permission.READ_MEDIA",
           "reason": "$string:reason"
         },
         {
           "name" : "ohos.permission.WRITE_MEDIA",
           "reason": "$string:reason"
         }
       ]
     }
   }
   

2. Call requestPermissionsFromUser to request the permissions from end users in the form of a dialog box. This operation is required because the grant mode of both permissions is user_grant.

   let context = getContext(this) as common.UIAbilityContext;
   let atManager = abilityAccessCtrl.createAtManager();
   let permissions: Array<string> = ['ohos.permission.READ_MEDIA','ohos.permission.WRITE_MEDIA']
   atManager.requestPermissionsFromUser(context, permissions)
   .then((data) => {
       console.log("Succeed to request permission from user with data: " + JSON.stringify(data))
   }).catch((error) => {
       console.log("Failed to request permission from user with error: " + JSON.stringify(error))
   })
   

How do I obtain the camera status?

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

Solution

The cameraManager class provides a listener to subscribe to the camera status.

cameraManager.on('cameraStatus', (cameraStatusInfo) => {
  console.log(`camera : ${cameraStatusInfo.camera.cameraId}`);
  console.log(`status: ${cameraStatusInfo.status}`);
})

CameraStatus Enumerates the camera statuses. CAMERA_STATUS_APPEAR (0): A camera appears. CAMERA_STATUS_DISAPPEAR (1): The camera disappears. CAMERA_STATUS_AVAILABLE (2): The camera is available. CAMERA_STATUS_UNAVAILABLE (3): The camera is unavailable.

References

CameraStatus

Does SoundPool support audio in WMV format? Which formats are supported? (API version 10)

Solution

Currently, WMV is not supported. The supported formats are AAC, MPEG (MP3), FLAC, and Vorbis.

References

The formats supported by SoundPool are the same as those supported by the bottom layer. For details about the supported formats, see Audio Decoding.

How do I read the preview image of the camera? (API version 10)

Solution

You can call ImageReceiver.readLatestImage to obtain the preview image of the camera.

References

readLatestImage

How do I listen for recordings? (API version 10)

Solution

Audio-related listening of the system is implemented in AudioStreamManager. You can call on(type: 'audioCapturerChange', callback: Callback): void to listen for audio capturer changes.

References

onaudiocapturerchange

In which audio processing scenarios are 3A algorithms (AEC, ANC, and AGC) embedded? If they are embedded, is there any API related to audio 3A processing? How do I call them? Are independent switches provided for the 3A algorithms? Does the system support 3A in recording scenarios? If not, what is the solution? For example, how do I ensure the sound quality of audio recording when playing music? (API version 10)

Solution

The embedded 3A processing is automatically enabled for the audio stream with the STREAM_USAGE_VOICE_COMMUNICATION configuration. Currently, an independent switch is not provided. 3A is supported in recording scenarios. You need to configure AudioScene and SourceType to enable 3A processing in recording scenarios.

References

AudioCapturer