UWP提供的流号码无效PreviewState

Question

我想设置一个预览流和记录循环的按钮来保存最后10分钟，30秒等等。这工作得很好，直到我开始添加代码来处理旋转。

这是抛出的线。

await _mediaCapture.SetEncodingPropertiesAsync(MediaStreamType.VideoPreview, 
videoEncodingProperties, mediaPropertySet); 

这里是整个方法

public async Task<MediaCapture> PrepareRecordingAsync() { 
      try { 
       _mediaCapture = new MediaCapture(); 
       var allVideoDevices = await DeviceInformation.FindAllAsync(DeviceClass.VideoCapture); 
       var desiredDevice = allVideoDevices.FirstOrDefault(x => x.EnclosureLocation != null && x.EnclosureLocation.Panel == Panel.Back); 
       _cameraDevice = desiredDevice ?? allVideoDevices.FirstOrDefault(); 
       _rotationHelper = new CameraRotationHelper(_cameraDevice.EnclosureLocation); 

       _mediaCapture.Failed += MediaCapture_Failed; 

       var settings = new MediaCaptureInitializationSettings { VideoDeviceId = _cameraDevice.Id }; 
       await _mediaCapture.InitializeAsync(settings); 

       var encodingProfile = MediaEncodingProfile.CreateMp4(VideoEncodingQuality.Auto); 

       var rotationAngle = CameraRotationHelper.ConvertSimpleOrientationToClockwiseDegrees(_rotationHelper.GetCameraCaptureOrientation()); 
       Guid RotationKey = new Guid("C380465D-2271-428C-9B83-ECEA3B4A85C1"); 
       encodingProfile.Video.Properties.Add(RotationKey, PropertyValue.CreateInt32(rotationAngle)); 
       var videoEncodingProperties = _mediaCapture.VideoDeviceController.GetMediaStreamProperties(MediaStreamType.VideoPreview); 
       MediaPropertySet mediaPropertySet = new MediaPropertySet(); 
       await _mediaCapture.SetEncodingPropertiesAsync(MediaStreamType.VideoPreview, videoEncodingProperties, mediaPropertySet); 

       _ras = new InMemoryRandomAccessStream(); 
       _recording = await _mediaCapture.PrepareLowLagRecordToStreamAsync(encodingProfile, _ras); 

       DisplayInformation.AutoRotationPreferences = DisplayOrientations.Portrait; 
       ConcurrentRecordAndPhotoSupported = _mediaCapture.MediaCaptureSettings.ConcurrentRecordAndPhotoSupported; 
      } catch (UnauthorizedAccessException) { 
       // This will be thrown if the user denied access to the camera in privacy settings 
       System.Diagnostics.Debug.WriteLine("The app was denied access to the camera"); 
      } catch (Exception ex) { 
       System.Diagnostics.Debug.WriteLine("MediaCapture initialization failed. {0}", ex.Message); 
      } 
      return _mediaCapture; 
     } 

没有通过谷歌搜索找到的解决方案是任何帮助。

这基本上是对MSDN操作指南的修改。

编辑：如果我改变了违规行以下然后它工作正常。

_mediaCapture.SetPreviewRotation(VideoRotation.Clockwise90Degrees); 

Answer 1

我可以重现我的身边您的问题，它会抛出错误异常的代码行await _mediaCapture.SetEncodingPropertiesAsync(...);

提供的流号码无效。 PreviewState

根据

注意，这种旋转是由流，如CaptureElement或视频播放应用程序的消费者进行的，而物流中的实际像素仍然是SetEncodingPropertiesAsync方法保留原来的方向。

此方法由流的消费者执行。看起来您需要首先调用StartPreviewAsync()，然后才能设置预览旋转，以便预览流。更多详细信息，请参考Handle device orientation with MediaCapture的“将定向数据添加到相机预览流”部分。

开始预览后，调用助手方法SetPreviewRotationAsync设置预览旋转。

因此，更新您的代码片段如下，它将工作。

_mediaCapture = new MediaCapture(); 
var allVideoDevices = await DeviceInformation.FindAllAsync(DeviceClass.VideoCapture); 
var desiredDevice = allVideoDevices.FirstOrDefault(x => x.EnclosureLocation != null && x.EnclosureLocation.Panel == Windows.Devices.Enumeration.Panel.Back); 
_cameraDevice = desiredDevice ?? allVideoDevices.FirstOrDefault(); 
_rotationHelper = new CameraRotationHelper(_cameraDevice.EnclosureLocation); 
_mediaCapture.Failed += MediaCapture_Failed; 
var settings = new MediaCaptureInitializationSettings { VideoDeviceId = _cameraDevice.Id }; 
await _mediaCapture.InitializeAsync(settings); 

//Add the preview code snippet 
PreviewControl.Source = _mediaCapture; 
await _mediaCapture.StartPreviewAsync(); 

var encodingProfile = MediaEncodingProfile.CreateMp4(VideoEncodingQuality.Auto); 
var rotationAngle = CameraRotationHelper.ConvertSimpleOrientationToClockwiseDegrees(_rotationHelper.GetCameraCaptureOrientation()); 
Guid RotationKey = new Guid("C380465D-2271-428C-9B83-ECEA3B4A85C1"); 
encodingProfile.Video.Properties.Add(RotationKey, PropertyValue.CreateInt32(rotationAngle)); 
var videoEncodingProperties = _mediaCapture.VideoDeviceController.GetMediaStreamProperties(MediaStreamType.VideoPreview); 
MediaPropertySet mediaPropertySet = new MediaPropertySet(); 
await _mediaCapture.SetEncodingPropertiesAsync(MediaStreamType.VideoPreview, videoEncodingProperties, mediaPropertySet); 

更多详情请参考official sample。