Avoid delay between Play() and the actual playback

Question

I'm trying to play a local media file using LibVLCSharp and to overlay a metronome sound on top of it. Here's a simplified version of the code I've been using:

private LibVLC libVlc;
private MediaPlayer mediaPlayer;

async Task Open()
{
    libVlc = new LibVLC();
    Core.Initialize();
    Media media = new(libVlc, new Uri(MEDIA_FILE_PATH));
    await media.Parse();
    mediaPlayer = new MediaPlayer(media);
}

async Task Play()
{
    PeriodicTimer metronomeTimer = new(METRONOME_TIMER_INTERVAL);
    mediaPlayer.Play();
    for (int i = 0; i < 10; i++)
    {
        PlayMetronomeSound();
        await metronomeTimer.WaitForNextTickAsync();
    }
}

This code works fine, but there is a small delay between the metronome sound and the media played by LibVLC. If I subscribe to the mediaPlayer.Playing event, I see that this event is fired about 150 ms after the mediaPlayer.Play() call. I assume, it's buffering the media during that time?

If that's the case, is there a way to pre-buffer the media in the Open() method to avoid the delay in Play()?

The only workaround I was able to find is to call mediaPlayer.Play() in the Open() method, then mediaPlayer.Pause() in the mediaPlayer.Playing event handler, and then seek to the beginning using mediaPlayer.SeekTo(TimeSpan.Zero). In this case, the second call of mediaPlayer.Play() starts the playback immediately and there are no more synchronization issues, but this feels like a hack to me.

Answer 1

You could try the following custom libvlc option --start-paused (in libvlc constructor) or :start-paused as a Media.AddOption argument. This may produce the result you're after.

Also, why not call PlayMetronomeSound when the Playing event fires?