public OggVorbisComment(IntPtr ptr, Encoding textEncoding)
 {
     c             = (VorbisComment)Marshal.PtrToStructure(ptr, typeof(VorbisComment));
     text_encoding = textEncoding;
 }
 internal OggVorbisComment(VorbisComment c, Encoding textEncoding)
 {
     this.c        = c;
     text_encoding = textEncoding;
 }