Saturday, August 25, 2012

M3U.NET: Parsing and Output of .m3u files in .NET

I've been reorganizing my media library using the very cool MusicBrainz Picard, but of course all my m3u files broke. So I wrote the free M3U.NET library, and then wrote a utility called FixM3U that regenerates an M3U file by searching your music folder for the media files based on whatever extended M3U information is available:

> FixM3u.exe /order:title,artist foo.m3u bar.m3u ...

The M3U.NET library itself has a fairly simple interface:

// Parsing M3U files.
public static class M3u
{
  // Write a media list to an extended M3U file.
  public static string Write(IEnumerable<MediaFile> media);
  // Parse an M3U file.
  public static IEnumerable<MediaFile> Parse(
         string input,
         DirectiveOrder order);
  // Parse an M3U file.
  public static IEnumerable<MediaFile> Parse(
         IEnumerable<string> lines,
         DirectiveOrder order);
}

The 3 exported types are straightforward. A MediaFile just has a full path to the file itself and a list of directives supported by the extended M3U format:

// A media file description.
public sealed class MediaFile
{
    // The full absolute path to the file.
    public string Path { get; set; }
    // Extended M3U directives.
    public List<MediaDirective> Directives { get; set; }
}

The directives are represented in this library as key-value pairs:

// An extended M3U directive.
public struct MediaDirective
{
    // The directive name.
    public string Name { get; set; }
    // The directive value.
    public string Value { get; set; }
    // The separator delineating this field from the next.
    public char? Separator { get; set; }
}

The currently supported keys are "Artist", "Title" and "Length".

The M3U format is supposed to order directives as "length, artist - title", but iTunes seems to reverse the order of artist and title. I've thus made this configurable via a parsing parameter of type DirectiveOrder, and you can specify the ordering when parsing:

// The order of the title and artist directives.
public enum DirectiveOrder
{
    // Artist followed by title.
    ArtistTitle,
    // Title followed by artist.
    TitleArtist,
}

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