c# - UWP提供的流号无效PreviewState

我试图通过按钮设置预览流和录制循环，以保存最后的10分钟，30秒等。在我开始添加代码以处理旋转之前，这种方法一直很好。

这是抛出的线。

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

这是整个方法

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;
        }

通过Google搜索找到的解决方案均无济于事。

这基本上是对MSDN操作方法的修改。

编辑：如果我将违规行更改为以下内容，则可以正常工作。

_mediaCapture.SetPreviewRotation(VideoRotation.Clockwise90Degrees);

最佳答案

我可以重现您的问题，它将在代码行await _mediaCapture.SetEncodingPropertiesAsync(...);上引发错误异常


  提供的流编号无效。
  预览状态


根据SetEncodingPropertiesAsync方法


  请注意，此旋转是由流的使用者（例如CaptureElement或视频播放器应用程序）执行的，而流中的实际像素仍保持其原始方向。


此方法由流的使用者执行。似乎您需要首先调用StartPreviewAsync()，然后再设置预览旋转，以便获得预览流。更多详细信息，请参考Handle device orientation with MediaCapture的“向相机预览流添加方向数据”部分。


  开始预览后，调用辅助方法SetPreviewRotationAsync设置预览旋转。


因此，按照以下方式更新代码段将可以正常工作。

_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);

更多详细信息，请参考official sample。

关于c# - UWP提供的流号无效PreviewState，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/43402721/