/// <summary>
/// Read the ID3 meta data extracting required tag values
/// </summary>
/// <param name="reader"></param>
/// <param name="majorVersion"></param>
/// <param name="maxPosition"></param>
/// <param name="tags"></param>
private static void ReadFrames(BinaryReader reader, int majorVersion, int maxPosition, MP3Tags tags)
{
// These are the tags that are currently being searched for
HashSet <string> requiredTags = (majorVersion == 2) ? new HashSet <string>()
{
"TP1", "TP2", "TT2", "TAL", "TRK", "TYE", "TCO"
}
: new HashSet <string>()
{
"TPE1", "TPE2", "TIT2", "TALB", "TRCK", "TYER", "TCON"
};
int nameSize = (majorVersion == 2) ? 3 : 4;
// Put the tag contents here
Dictionary <string, byte[]> frames = new Dictionary <string, byte[]>();
bool endOfTags = false;
while ((reader.BaseStream.Position < maxPosition) && (endOfTags == false))
{
Logger.Log(string.Format("Position at start of frame {0}", reader.BaseStream.Position));
// Check for end of the frames
char frameNameFirstChar = reader.ReadChar();
if (frameNameFirstChar == '\0')
{
endOfTags = true;
}
else
{
// Get the rest of the tag name and its contents
string frameName = frameNameFirstChar + new string( reader.ReadChars(nameSize - 1));
ulong frameSize = ReadFrameSize(reader, nameSize, majorVersion);
Logger.Log(string.Format("Frame {0}, size {1}", frameName, frameSize));
// Skip a couple of bytes and then read the frame contents
reader.ReadByte();
reader.ReadByte();
// Only store if it is one of the required tags
if (requiredTags.Contains(frameName) == true)
{
frames[frameName] = (frameSize > 0) ? reader.ReadBytes(( int )frameSize) : new byte[0];
requiredTags.Remove(frameName);
endOfTags = (requiredTags.Count == 0);
}
else
{
// Still need to skip over the frame contents
if (frameSize > 0)
{
Logger.Log(string.Format("Position before skipping {0} bytes is {1}", frameSize, reader.BaseStream.Position));
reader.ReadBytes(( int )frameSize);
Logger.Log(string.Format("Position after skipping bytes {0}", reader.BaseStream.Position));
}
}
}
}
// Now all the required frames have been obtained, extract the contents and assign to the tag instance
if (majorVersion == 2)
{
tags.Artist = GetStringTag(frames, "TP1");
tags.AlbumArtist = GetStringTag(frames, "TP2");
tags.Title = GetStringTag(frames, "TT2");
tags.Album = GetStringTag(frames, "TAL");
tags.Track = GetStringTag(frames, "TRK");
tags.Year = GetStringTag(frames, "TYE");
tags.Genre = GetStringTag(frames, "TCO");
}
else
{
tags.Artist = GetStringTag(frames, "TPE1");
tags.AlbumArtist = GetStringTag(frames, "TPE2");
tags.Title = GetStringTag(frames, "TIT2");
tags.Album = GetStringTag(frames, "TALB");
tags.Track = GetStringTag(frames, "TRCK");
tags.Year = GetStringTag(frames, "TYER");
tags.Genre = GetStringTag(frames, "TCON");
}
// Log.WriteLine( LogPriority.Debug, "MobileApp:ReadFrames", string.Format( "Artist: {0} Title: {1} Album: {2} Track: {3}", tags.Artist, tags.Title, tags.Album,
// tags.Track ) );
}
/// <summary>
/// Extract MP3 tags and duration from the MP3 stream
/// </summary>
/// <param name="fileStream"></param>
/// <returns></returns>
public static MP3Tags GetFileTags(Stream fileStream)
{
MP3Tags tags = new MP3Tags();
using (BinaryReader reader = new BinaryReader(fileStream))
{
try
{
// Make sure the file is at least 10 bytes long to determine the size of the ID3 header
if (reader.BaseStream.Length >= 10)
{
// Look at the start of the file for the ID3 tags
if (new string( reader.ReadChars(3)) == "ID3")
{
// Start extracting metadata
// ID3 version
byte majorVersion = reader.ReadByte();
// Skip the minor version
reader.ReadByte();
// Skip next 'flags' byte
reader.ReadByte();
// The size of the ID3 header
ulong headerSize = ReadEncodedSize(reader, 4);
if (headerSize > 0)
{
// Get all the required ID3 tags
int id3EndPosition = ( int )headerSize + 10;
ReadFrames(reader, majorVersion, id3EndPosition, tags);
// Step on past the ID3 frames and attempt to read the first MP3 frame
if ((reader.BaseStream.Position < id3EndPosition) && (reader.BaseStream.Length >= id3EndPosition))
{
reader.ReadBytes(id3EndPosition - ( int )reader.BaseStream.Position);
// The first MP3 frame does not always follow the end of the ID3 header, so go searching for the
// MP3 synch pattern
bool mp3HeaderFound = false;
long readLimit = reader.BaseStream.Position + 0x1000;
long searchStart = reader.BaseStream.Position;
byte[] mp3Header = new byte[] { 0, 0, 0 };
while ((mp3HeaderFound == false) && (reader.BaseStream.Position < reader.BaseStream.Length) &&
(reader.BaseStream.Position < readLimit))
{
mp3Header[1] = reader.ReadByte();
if ((mp3Header[0] == 0xFF) && ((mp3Header[1] & 0xE0) == 0xE0))
{
// Synch bytes found
mp3HeaderFound = true;
// Get the last byte of the header
mp3Header[2] = reader.ReadByte();
// Parse the MP3 frame and determine the duration of the file
tags.Length = ParseMp3Frame(reader, mp3Header);
}
else
{
mp3Header[0] = mp3Header[1];
}
}
if (mp3HeaderFound == false)
{
Logger.Log(string.Format("MP3 frame not found between {0} and {1}", searchStart, reader.BaseStream.Position));
}
}
else
{
Logger.Log(string.Format("ID3 frame is truncated"));
}
}
}
else
{
Logger.Log(string.Format("Header is not ID3"));
}
}
else
{
Logger.Log(string.Format("Could not read header"));
}
}
catch (Exception tagsException)
{
Logger.Log(string.Format("Problem reading file: {0}", tagsException.Message));
}
}
return(tags);
}
