使用MediaCapture时，长宽比/缩放级别更改是否存在问题？

Question

I am using MediaCapture along with CapturePreview to create a preview stream on a Surface Pro tablet. I am taking photos periodically with a timer using

CapturePhotoToStreamAsync()

Whenever a photo is taken though, the preview stream zooms out slightly as if it is changing the resolution or aspect ratio or something similar.

I found this issue , which sounds exactly the same, but I can't seem to resolve it regardless of the resolutions set.

This is the bit of code I have to grab Bitmap objects from the stream:

using (var randomAccessStream = new InMemoryRandomAccessStream())
{
    await mediaCap.CapturePhotoToStreamAsync(imageProps, randomAccessStream);

    randomAccessStream.Seek(0);
    using (var ioStream = randomAccessStream.AsStream())
    {
        BitmapImage bitmapImage = new BitmapImage();
        bitmapImage.BeginInit();
        bitmapImage.StreamSource = ioStream;
        bitmapImage.CacheOption = BitmapCacheOption.OnLoad;
        bitmapImage.EndInit();
        bitmapImage.Freeze();
    }
}

imageProps is being set to 1280x720, the same resolution as the preview object. This wouldn't be a huge issue if it only happened occasionally, but I need to grab frames frequently (multiple times per second), and it looks very jarring.

Edit:

Something to note is that the issue only occurs on the mentioned Surface Pro tablet (2736x1824 @200%), it doesn't appear to occur on a 1920x1080 screen.

Answer 1

The solution I ended up finding was this change:

From:

await _mediaCaptureObject.InitializeAsync(new MediaCaptureInitializationSettings
{
    VideoDeviceId = deviceList?.FirstOrDefault(x => x.Name.Contains("Camera Name"))?.Id,
    StreamingCaptureMode = StreamingCaptureMode.Video
});

To:

await _mediaCaptureObject.InitializeAsync(new MediaCaptureInitializationSettings
{
    VideoDeviceId = deviceList?.FirstOrDefault(x => x.Name.Contains("Camera Name"))?.Id,
    StreamingCaptureMode = StreamingCaptureMode.Video,
    PhotoCaptureSource = PhotoCaptureSource.VideoPreview
});

This doesn't really explain the issue I was seeing, since I was setting the ImageEncodingProperties to the same resolution as the stream when capturing the photo. Anyway, the default PhotoCaptureSource is Auto , which must've been using the Photo mode instead of VideoPreview . Once I changed this, the issue stopped appearing.