Question

我正在使用一种设计来一个接一个地播放wav文件。此设计基于mediaEnded事件并且工作正常。当试图在非常短的wav文件上暗示此设计时，并不总是引发mediaEnded事件。他们是解决这个问题的方法吗？感谢。

Answer 1

我使用计时器实施了一种解决方法，以定期检查两种情况：

自上次检查后视频播放位置未移动 - 表示视频已卡住。
视频播放位置超出了视频的结尾 - 表示视频正在播放，但通常只会显示黑屏。

如果存在任何一种情况，则强制下一个视频开始播放。

请注意，这是类文件中代码的摘录。

namespace XXXX
{
    public partial class VideoWindow :  Window
    {

        private DispatcherTimer mediaPositionTimer;  // We check the play position of the video each time this fires to see if it has hung
        double _lastPosition = -1;
        int _video_count;
        int videoDuration;  
        DateTime lastVideoStartTime;

        public VideoWindow()
        {
            adMediaElement.LoadedBehavior = MediaState.Manual;

            adMediaElement.MediaEnded  += adMediaElement_MediaEnded;
            adMediaElement.MediaOpened += adMediaElement_MediaOpened;
            adMediaElement.MediaFailed += adMediaElement_MediaFailed;

        }

        // Increment the counter every time we open a video
        void adMediaElement_MediaOpened(object sender, RoutedEventArgs e)
        {
            Log("Media opened");
            _video_count++;
        }

        // If we have a failure then just start the next video
        void adMediaElement_MediaFailed(object sender, ExceptionRoutedEventArgs e)
        {
            Log("Media failed");
            this.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Normal, new Action(delegate()
            {
                PlayNextMedia();
            }));
        }

        // When a video ends start the next one
        private void adMediaElement_MediaEnded(object sender, RoutedEventArgs e)
        {
           Log("MediaEnded called");
            this.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Normal, new Action(delegate()
            {
                PlayNextMedia();
            }));
        }

        // Stops and Closes any existing video
        // Increments the file pointer index
        // Switches to display ads if no more videos
        // else
        // Starts the video playing
        private void PlayNextMedia()
        {
           // Log(String.Format("PlayNextMedia called"));

            //Close the existing file and stop the timer
            EndVideo2();
            adMediaElement.Dispatcher.Invoke(System.Windows.Threading.DispatcherPriority.Normal, new Action(delegate()
                {
                    adMediaElement.Stop();
                    adMediaElement.Close();
                }));

            currentMediaFileIndex++;

            if (currentMediaFileIndex > (mediaFileCount - 1))
            {
                Log(String.Format("  switching to Ads, currentMediaFileIndex = {0}", currentMediaFileIndex));
                // Now setup and then run static adds for 10 minutes
                currentMediaFileIndex = 0;
                StartAds();

            }
            else
            {
                Log(String.Format("  switching media, index = {0}", currentMediaFileIndex));
                adMediaElement.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Normal, new Action(delegate()
                {
                    StartVideo2();
                }));
            }
        }

        // Stops the mediaPositionTimer, must be called in conjunction with a admediaElement.Pause() or Stop()
        private void EndVideo2()
        {
           // Log("EndVideo2() called");
            _is_playing = false;
            // Stop the timer
            if (mediaPositionTimer != null)
            {
                mediaPositionTimer.Stop();
            }
        }

        // Load the media file
        // Set the volume
        // Set the lastVideoStartTime variable
        private void StartVideo2()
        {
           // Log("StartVideo2() called");
            loadMediaFile(currentMediaFileIndex);

            adMediaElement.Volume = Properties.StationSettings.Default.VolumeMedia;
            lastVideoStartTime = DateTime.Now;  // Record the time we started

            // Stop the timer if it exists, otherwise create a new one
            if (mediaPositionTimer == null)
            {
                mediaPositionTimer = new DispatcherTimer();
                // Set up the timer     
                mediaPositionTimer.Interval = TimeSpan.FromSeconds(10);
                mediaPositionTimer.Tick += new EventHandler(positionTimerTick);
            }
            else
            {
                mediaPositionTimer.Stop();
            }
            // Start it running
            adMediaElement.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Normal, new Action(delegate()
                {
                    mediaPositionTimer.Start();
                    _is_playing = true;
                    adMediaElement.Play();
                }));
        }


        private void RestartVideo2()
        {
            //Log("Restart the video");
            adMediaElement.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Normal, new Action(delegate()
                {
                    mediaPositionTimer.Start();
                    _is_playing = true;
                    adMediaElement.Play();
                }));
        }

        // Check the playback position of the mediaElement has moved since the last check, 
        //  if not then the video has hung
        // Also check if the playback position exceeds the video duration,
        //  if so it has also hung
        // If video has hung then force the next one to start and report a Warning
        private void positionTimerTick(object sender, EventArgs e)
        {
            double duration;
            double currentPosition = adMediaElement.Position.TotalSeconds;

            if (adMediaElement.NaturalDuration.HasTimeSpan)
            {
                duration = adMediaElement.NaturalDuration.TimeSpan.TotalSeconds;
            }
            else
            {
                duration = 5 * 60; // Default to 5 minutes if video does not report a duration
            }

            if ((currentPosition == lastPosition) || currentPosition > (duration + 30))
            {
                // do something
                //Log("*** Video position has exceed the end of the media or video playback position has not moved ***");

                if (_is_playing)
                {
                    String logString = String.Format("*** Video {0} has frozen ({1}c:{2}l:{3}d)so forcing the next one to start ***", mediaFiles[currentMediaFileIndex], currentPosition, lastPosition, duration);
                    Log(logString);

                    PlayNextMedia();

                    // Send a message indicating we had to do this
                    mainWindow.SendHeartbeat(MainWindow.STATUS_WARNING, logString);

                }
            }
            lastPosition = currentPosition;
        }

    }
}

mediaEnded事件并不总是激发

1 个答案: