How to get the duration of mp3 file without playing or storing them

Question

I am building a wp8 app which could play poems line by line displayed in listbox.

Say I have 20 lines of Poems showing as 20 items in listbox. I have 20 mp3 files (one for each line), I used BackgroundAudioPlayer to play individual files and select each item (poem) in listbox. During playback of these mp3 files, there were delays of 1-3 seconds, so I found the full version of these mp3 files (20 files merged into one), reading poems line by line.

I am playing this mp3 file using BackgroundAudioPlayer. Playing as one file, I cannot select each item in listbox as I don't know the line number by playing one mp3 file.

Now what I want is to store the duration of 20 files in seconds, without storing and playing. The files are located in a link (http:123.com/1.mp3, /2.mp3, ...)

I used AudioTrack with absolute path and then used duration property, but it always returns zero. How can I get the duration of an mp3 file without playing them?

Edited: In the background Agent I did below:

protected override void OnPlayStateChanged(BackgroundAudioPlayer player, AudioTrack track, PlayState playState)
{
switch (playState)
{
case PlayState.TrackReady:
TrackDuration tr = DataSource.Connection.Table<TrackDuration>().SingleOrDefault();
if (tr.IsGetTrackDuration)
{
if (player.Track != null)
{
player.Position = TimeSpan.FromSeconds(player.Track.Duration.TotalSeconds);
Recitation r = DataSource.Connection.Query<Recitation>("select * from Recitation where ID = " + player.Track.Title).SingleOrDefault();
r.AyaDuration = player.Track.Duration.TotalSeconds;
DataSource.saveRecitionDownloaded(r);
PlayNextTrack(player);
}
}
break;
}
NotifyComplete();
}

protected override void OnUserAction(BackgroundAudioPlayer player, AudioTrack track, UserAction action, object param)
{
switch (action)
{
case UserAction.Play:
   PlayTrack(player);
break;
case UserAction.Seek:
if (null!=player.Track)
player.Position = (TimeSpan)param;
break;
}
NotifyComplete();
}

private void PlayNextTrack(BackgroundAudioPlayer player)
{
 if (++currentTrackNumber >= audioTrack.Count)
   return;
 PlayTrack(player);
}

private void PlayTrack(BackgroundAudioPlayer player)
{
//If No Track then load Track
 if (audioTrack.Count == 0)
 {
     //Load Tracks and Add them into Track Play List
 }
if ((player.Track == null) || (player.Track.Title != audioTrack[currentTrackNumber].Title))
    player.Track = audioTrack[currentTrackNumber];

if ((player.Track != null) && (player.PlayerState != PlayState.Playing))
    player.Play();
}

The question is It plays some of the files which I don't want. (tr.IsGetTrackDuration) is always true, but I don't know why it plays some?

Answer 1

Ok I have a thought here. Under the AudioPlayer class, there is a TrackReady event that is set by default to play the track. Instead of playing by default, set a bool to true if you're simply wanting to obtain the duration, and false if you actually wish to play a track (when you're wanting to play the full mp3).

The bool value would have to be set in the main app before the track is set, and then read in the AudioPlayer each time the OnPlayStateChanged is called.

protected override void OnPlayStateChanged(BackgroundAudioPlayer player, AudioTrack track, PlayState playState)
{
    //read GettingDuration value here

    try
    {
        switch (playState)
        {
            case PlayState.TrackReady:
                if (GettingDuration)
                {
                //store duration somehow and get the next track in line
                }
                else
                {
                    player.Play();
                }

                break;
        }
    }
}

Answer 2

MusicProperties class has a property for the duration

 MusicProperties musicProperties = await file.Properties.GetMusicPropertiesAsync();
 outputText.AppendLine("Duration: " + musicProperties.Duration);