Question

I’m currently developing a WPF application which requires strictly timing, says, being late 2 seconds matters.

I have a MediaElement mediaPlayer which seeks to a new position and play every time a Dispatcher timer is fired. But I notice that the mediaPlayer.Position is not very synced with the timer. In the example below, I set the dispatcherTimer fired after 55 seconds, but the value received from MessageBox in timer_Tick is 108.276746, which is late 2 seconds (55 + 55 = 110).

private void button1_Click(object sender, RoutedEventArgs e)
        {
            DispatcherTimer timer = new DispatcherTimer();
            timer.Interval = TimeSpan.FromSeconds(55);
            timer.Tick += new EventHandler(timer_Tick);
            mediaPlayer.Source = new Uri("test.wma", UriKind.Relative);
            _currentPosition = 55;
            mediaPlayer.Position = TimeSpan.FromSeconds(_currentPosition);

            timer.Start();
        }
void timer_Tick(object sender, EventArgs e)
        {
            MessageBox.Show("Position" + mediaPlayer.Position.TotalSeconds);// print around 108 seconds
        }

This is the problem because I need the mediaPlayer position is perfectly synced with the dispatcher timer.

For more information, the root problem here is: the dispatcher timer to strictly follow the mediaElement progress, because I need to sync other controls with the position that mediaPlayer. Being late 2 seconds is unacceptable. Does anyone know how to achieve this effect?

UPDATE PURPOSE: I’m trying to “switch illustration image” according to the playing position from an audio. For example, when the narrator read to “… We have a beautiful house” in the audio, the program will show pictures of a beautiful building. But now since the position is late, it will show the picture long before the audio mentions it.

Answer 1

As pointed out, it takes time for the media elements to load, therefore it is not wise to use a countdown timer. You should do the the other way round: the DispatchTimer fires say like 1 or 2 times every second, and when it’s fired you check the position of the media element. If it’s at a certain position then show the picture.

This approach also limits the maximum error do the time interval of your DispatchTimer events, assuming that the system fires them accurately.