如何在Windows Phone 8,8.1中更改默认视频捕获分辨率

Question

I want build an app that will give users options to choose the resolution size of video recording (such as full HD-1920x1080 or vga-640x480 etc.)

I am using the code below but when I run this on 720p emulator, it shows the message which is in else part ie camera not support this. (when I change the value 800,450 , to 640 ,480 camera start working normally)

try
           {
              //string deviceName = DeviceStatus.DeviceName;
               //var deviceName = DeviceStatus.DeviceName;
               //if (deviceName.Contains("RM-885"))
               //{
                   Windows.Foundation.Size initialResolution = new Windows.Foundation.Size(800, 450);
                   Windows.Foundation.Size previewResolution = new Windows.Foundation.Size(800, 450);
                   Windows.Foundation.Size captureResolution = new Windows.Foundation.Size(800, 450);
                   if (AudioVideoCaptureDevice.AvailableSensorLocations.Contains(CameraSensorLocation.Back))
                   {
                       pops = await AudioVideoCaptureDevice.OpenAsync(CameraSensorLocation.Back, initialResolution);
                       await pops.SetPreviewResolutionAsync(previewResolution);
                       await pops.SetCaptureResolutionAsync(captureResolution);    


                   }
               }
          // }

           catch (Exception p) { Debug.WriteLine(p.Message); }

            try
            {
                if(pops != null)
                {


                    // create the videobrush for the viewfinder
                    videoRecordBrush = new VideoBrush();
                    videoRecordBrush.SetSource(pops);
                    // display the viewfinder image 
                    viewfinderRectangle.Fill = videoRecordBrush;
                    //shows available resolution message 
                    MessageBox.Show("statrt recording ");
                    MessageBox.Show(pops.PreviewResolution.ToString());
                    MessageBox.Show(pops.CaptureResolution.ToString());


                }
                else
                {
                    MessageBox.Show("camera not support this ");
                }
            }
            catch(Exception ex)
            {
                MessageBox.Show("exception" + ex);
            }
        }

Is this right code to change the resolution in video mode? or is there any other method?

Answer 1

In Windows Phone 8.1, u can change the aspect ratio of both video preview and captured photo by changing the MediaCapture.VideoDeviceController setting.

Video preview is the view of camera you can see from your screen before you actually capture a photo. It is essential for the aspect ratio of video preview and captured photo to be the same to avoid weird lines & black bars in the captured photo. In other words, it is to ensure the photo captured to be exactly the same as the preview you see on the screen.

First, you can check all the available resolutions in your Windows Phone 8.1. In the following code, I demonstrate how to check resolutions available for video preview & captured photo. The height&width returned is the resolutions available for your phone, eg at i=0, height=1080, width=1920 (1920x1080). Please debug at the height&width line to check for different resolution.

MediaCapture mediacapture = new MediaCapture();
await mediacapture.InitializeAsync(new MediaCaptureInitializationSettings{});
var previewResolution = mediacapture.VideoDeviceController.GetAvailableMediaStreamProperties(MediaStreamType.VideoPreview);
var photoResolution = mediacapture.VideoDeviceController.GetAvailableMediaStreamProperties(MediaStreamType.Photo);

        VideoEncodingProperties allResolutionsAvailable;
        uint height, width;
  //use debugger at the following line to check height & width for video preview resolution
        for (int i = 0; i < previewResolution.Count; i++)
        {
            allResolutionsAvailable = previewResolution[i] as VideoEncodingProperties;
            height = allResolutionsAvailable.Height;
            width = allResolutionsAvailable.Width;
        }
  //use debugger at the following line to check height & width for captured photo resolution
        for (int i = 0; i < photoResolution.Count; i++)
        {
            allResolutionsAvailable = photoResolution[i] as VideoEncodingProperties;
            height = allResolutionsAvailable.Height;
            width = allResolutionsAvailable.Width;
        }

After checking all the available resolutions from the height and width parameter above, you can select the particular resolutions you want by using .ElementAt(int) method, eg .ElementAt(0)

var selectedPreviewResolution = mediacapture.VideoDeviceController.GetAvailableMediaStreamProperties(MediaStreamType.VideoPreview).ElementAt(1);
var selectedPhotoResolution = mediacapture.VideoDeviceController.GetAvailableMediaStreamProperties(MediaStreamType.Photo).ElementAt(1);

await mediacapture.VideoDeviceController.SetMediaStreamPropertiesAsync(MediaStreamType.VideoPreview, selectedPreviewResolution);
await mediacapture.VideoDeviceController.SetMediaStreamPropertiesAsync(MediaStreamType.Photo, selectedPhotoResolution);

//in .xaml <CaptureElement Name="viewfinder"/>
viewfinder.Source = mediacapture;
//to set video preview upright
mediacapture.SetPreviewRotation(VideoRotation.Clockwise90Degrees);
await mediacapture.StartPreviewAsync();

Set .ElementAt(i) for Video Preview & Captured Photo separately at the same aspect ratio. Below are the resolutions available for Nokia Lumia 1520.

Video Preview

• i.....height*width..aspect ratio
• 0.....1080*1920....16:9
• 1......720*1280.....16:9
• 2......450*800.......16:9
• 3....1080*1440......4:3
• 4......768*1024......4:3
• 5......480*640........4:3

Captured photo

• i.... height*width..aspect ratio
• 0.... 3024*4992.......4:3
• 1.....1936*2592...162:121
• 2.....1536*2048.......4:3
• 3......480*640..........4:3
• 4.....3024*5376.....16:9
• 5.....1728*3072.....16:9
• 6.....1456*2592...162:91

Lastly, if you want to use the maximum resolution available for both Video Preview & Captured Photo, you can use the following code instead.

//maximum resolution for 4:3 aspect ratio 
 var maxPhotoResolution = mediacapture.VideoDeviceController.GetAvailableMediaStreamProperties(MediaStreamType.Photo).Aggregate((i1, i2) => (i1 as VideoEncodingProperties).Height > (i2 as VideoEncodingProperties).Height ? i1 : i2);
 var maxPreviewResolution = mediacapture.VideoDeviceController.GetAvailableMediaStreamProperties(MediaStreamType.VideoPreview).Aggregate((i1, i2) => (i1 as VideoEncodingProperties).Height > (i2 as VideoEncodingProperties).Height ? i1 : i2);

//maximum resolution for 16:9 aspect ratio 
 var maxPhotoResolution = mediacapture.VideoDeviceController.GetAvailableMediaStreamProperties(MediaStreamType.Photo).Aggregate((i1, i2) => (i1 as VideoEncodingProperties).Width > (i2 as VideoEncodingProperties).Width ? i1 : i2);
 var maxPreviewResolution = mediacapture.VideoDeviceController.GetAvailableMediaStreamProperties(MediaStreamType.VideoPreview).Aggregate((i1, i2) => (i1 as VideoEncodingProperties).Width > (i2 as VideoEncodingProperties).Width ? i1 : i2);

await mediacapture.VideoDeviceController.SetMediaStreamPropertiesAsync(MediaStreamType.Photo, maxPhotoResolution);
await mediacapture.VideoDeviceController.SetMediaStreamPropertiesAsync(MediaStreamType.VideoPreview, maxPreviewResolution);

Answer 2

如果要对录制的视频进行更多控制，则应使用新的Windows Phone 8 API： AudioVideoCaptureDevice ，它具有SetCaptureResolutionAsync方法。