Question

我正在学习如何使用WPF mediaelement控制视频的教程。对于大多数部件，除了倒带视频功能外，一切都很好。我试图寻找解决方案并遇到一个线程，建议暂停视频并改变视频播放的位置。所以我尝试了这个：

//timer updates the position of the slider
if(flagRewind == true)
{
    try
    {
        if (playVideoMediaElement.NaturalDuration.HasTimeSpan)
        {
            //step the video back every second
            playVideoMediaElement.Position -= TimeSpan.FromMilliseconds(1000);

            videoSlider.Value = playVideoMediaElement.Position.TotalSeconds;
            //we have re-winded to the zero position of the slider
            if (videoSlider.Value <= 0)
            {
                //the video is done playing
                playVideoMediaElement.Stop();
                //get tag of button click, to change button icon appropriately             (pause[||]/play [>])
                tag = playPauseVideoButton.Tag.ToString(); 
                //call method that changes the button image icon to either [||] or [>]
                ChangePlayPauseButtonImageIcon();
                IsPlaying(false);
                playPauseVideoButton.IsEnabled = true;
                //we are done re-winding
                flagRewind = false;   
            }
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show("Error: " + ex.Message);
    }
}

这有效，但它正在跳帧，我尝试使用这样的按钮点击事件加速：

private void slowPlayVideoButton_Click(object sender, RoutedEventArgs e)
{
  playVideoMediaElement.SpeedRatio = (double)-1;
}

但这只是停止（冻结）视频。如何使用速度比率平滑地回放视频？ #Thanks！

Answer 1

我所做的只是通过增加TimeSpan值来更改计时器间隔，我还更改了媒体元素的TimeSpan。代码现在看起来：

if(flagRewind == true)
{
    //change the timer interval
    timer.Interval = TimeSpan.FromMilliseconds(50.0);
    try
    {
        if (playVideoMediaElement.NaturalDuration.HasTimeSpan)
        {
            //step the video back every second
            playVideoMediaElement.Position -= TimeSpan.FromMilliseconds(50.0);
            videoSlider.Value = playVideoMediaElement.Position.TotalSeconds;

            if (videoSlider.Value <= 0)
            {
                //the video is done playing
                playVideoMediaElement.Stop();

                tag = playPauseVideoButton.Tag.ToString(); 
                ChangePlayPauseButtonImageIcon();
                IsPlaying(false);
                playPauseVideoButton.IsEnabled = true;

                flagRewind = false;   
            }
        }

这对我来说非常好，当用户按下前进||时播放按钮我只是默认定时器间隔和媒体元素位置值。

Media Element speedratio rewind不起作用

1 个答案: