How to record video using AudioVideoCptureDevice i

问题:

Here its stated that I can record video using AudioVideoCaptureDevice but there is no sample or help provided.

I need to do the following things:
- record the video into a stream DONE
- display a thumbnail of video recorded (can be a frame captured while video recording) DONE
- replay the video recorded DONE
- change resolution and type of camera (front/back) DONE

How to achieve this? Are there any samples? I am unable to find them. Please help me.

DONE
- record the video into a stream
- replay the video recorded
- change resolution and type of camera (front/back)
- display a thumbnail of video recorded (can be a frame captured while video recording)

NEW PROBLEMS
- front camera video is mirror inverted. I am able to change this while recording using transform but the actual video is still mirrored.

UPDATE
- calculate the size of the recording video and display it. Its not working. Stream.Size is giving random values.

Any thoughts on solving these?

回答1:

For the problem of Displaying a Thumbnail of the video recording...there is an event called PreviewFrameAvailable on the AudioVideoCaptureDevice. I think if you setup this event handler it will tell you when the data is available to get a preview (image/thumbnail) of the video.

There are also 3 methods for grabbing a byte array of a preview image (GetPreviewBufferARGB, GetPreviewBufferY, GetPreviewBufferYCbCr). All three of these methods return a byte[] of the pixel data for the image in the corresponding format (ex: GetPreviewBufferARGB should return the raw bytes of a raw bitmap in ARGB format). After getting the byte array of the preview data you should be able to encode it as a PNG or JPEG or whatever compressed image format you prefer. Best of luck.

回答2:

The basics of using the Windows Phone 8 camera are covered here...

Advanced photo capture for Windows Phone 8

How to save a picture captured with the new camera’s API in the camera roll in Windows Phone 8

How to set video record resolution in Windows Phone 8

How to set advanced properties for video recording in WP8

Note: there are issues when getting the supported resolutions of the front camera on some Lumia devices

回答3:

I solved the problem of mirror inverted video recording through Front-Camera:

the one line that solved my problem is:

//here videoCapture is AudioVideoCaptureDevice object

videoCapture.SetProperty(KnownCameraGeneralProperties.EncodeWithOrientation, -90);

Full Code:

XAML code

    <Canvas x:Name="CanvasLayoutRoot" RenderTransformOrigin="0.5 0.5"
            Width="{Binding ActualHeight, ElementName=LayoutRoot}"
            Height="{Binding ActualWidth, ElementName=LayoutRoot}"
            Margin="-160 0 0 0">

        <Canvas.RenderTransform>
            <RotateTransform x:Name="rt" />
        </Canvas.RenderTransform>

        <Canvas.Background>
            <VideoBrush x:Name="videoBrush" />
        </Canvas.Background>
    </Canvas>

BackEnd C# code

    // in any specific method or event handler write
    // the below code while initializing the Front camera

    private AudioVideoCaptureDevice videoCapture = await AudioVideoCaptureDevice.OpenAsync(CameraSensorLocation.Front, new Windows.Foundation.Size(640, 480));
    videoCapture.SetProperty(KnownCameraGeneralProperties.EncodeWithOrientation, -90);
    rt.Angle = -90;
    videoBrush.SetSource(videoCapture);

This piece of code helped me after tens of efforts..!