Windows Phone 8.1 多媒体（2）：视频

原文:Windows Phone 8.1 多媒体（2）：视频

Windows Phone 8.1 多媒体（1）：相片

Windows Phone 8.1 多媒体（2）：视频

Windows Phone 8.1 多媒体（3）：音乐

（1）拍摄视频

拍摄视频和拍摄相片的方法是基本一致的：

MediaCapture mediaCapture;
MediaEncodingProfile videoEncodingProperties;

protected override async void OnNavigatedTo(NavigationEventArgs e)
{
    HardwareButtons.CameraHalfPressed += HardwareButtons_CameraHalfPressed;
    HardwareButtons.CameraReleased += HardwareButtons_CameraReleased;

    videoCaptrueElement.Source = await Initialize();
    await mediaCapture.StartPreviewAsync();
}

async void HardwareButtons_CameraHalfPressed(object sender, CameraEventArgs e)
{
    if( mediaCapture != null )
    {
        var video = await KnownFolders.VideosLibrary.CreateFileAsync("video.mp4", CreationCollisionOption.GenerateUniqueName);
await mediaCapture.StartRecordToStorageFileAsync(videoEncodingProperties, video);
    }
}

async void HardwareButtons_CameraReleased(object sender, CameraEventArgs e)
{
    if( mediaCapture != null )
    {
        await mediaCapture.StopRecordAsync();
    }
}

private async Task<MediaCapture> Initialize()
{
    mediaCapture = new MediaCapture();
    await mediaCapture.InitializeAsync();

    mediaCapture.VideoDeviceController.PrimaryUse = CaptureUse.Video;

    videoEncodingProperties = MediaEncodingProfile.CreateMp4(VideoEncodingQuality.Vga);

    return mediaCapture;
}

protected override void OnNavigatedFrom(NavigationEventArgs e)
{
    if( mediaCapture != null )
    {
        mediaCapture.Dispose();
        mediaCapture = null;
    }
}

（2）编辑视频

视频编辑的 API 在 Windows.Media.Editing 命名空间下，具体可看 MSDN：链接

简单的说就是把某些视频实例化为 MediaClip，然后将这些视频添加到 MediaComposition.Clips 中去，最后将这些视频拼接到一起或添加个 BackgroundAudioTrack 什么的：

MediaClip video = await MediaClip.CreateFromFileAsync(　　　　　　　　　　　　　　　　await StorageFile.GetFileFromApplicationUriAsync(new Uri("ms-appx:///thanks.mp4")));

MediaComposition videos = new MediaComposition();
videos.Clips.Add(video);

BackgroundAudioTrack bgm = await BackgroundAudioTrack.CreateFromFileAsync(　　　　　　　　　　　　　　　　　　　　await StorageFile.GetFileFromApplicationUriAsync(new Uri("Above Your Hand.mp3")));
videos.BackgroundAudioTracks.Clear();
videos.BackgroundAudioTracks.Add(bgm);

await videos.SaveAsync(await ApplicationData.Current.LocalFolder.CreateFileAsync("video.mp4", CreationCollisionOption.ReplaceExisting));

（3）录制手机屏幕视频

录制手机屏幕视频是 WP8.1 新加的 API，使用方法和拍摄视频差不多，只需将录制对象设为屏幕即可：

var screenCapture = ScreenCapture.GetForCurrentView();

mediaCapture = new MediaCapture();
await mediaCapture.InitializeAsync(new MediaCaptureInitializationSettings
{
    VideoSource = screenCapture.VideoSource,
    AudioSource = screenCapture.AudioSource,
});

var file = await KnownFolders.VideosLibrary.CreateFileAsync("screenrecording.mp4", CreationCollisionOption.ReplaceExisting);
await mediaCapture.StartRecordToStorageFileAsync(MediaEncodingProfile.CreateMp4(VideoEncodingQuality.Auto), file);

停止录制：

if( mediaCapture != null )
{
    await mediaCapture.StopRecordAsync();
    mediaCapture.Dispose();
    mediaCapture = null;
}