/*

  * Entagged Audio Tag library

  * Copyright (c) 2003-2005 Rapha�l Slinckx <raphael@slinckx.net>

  * 

  * This library is free software; you can redistribute it and/or

  * modify it under the terms of the GNU Lesser General Public

  * License as published by the Free Software Foundation; either

  * version 2.1 of the License, or (at your option) any later version.

  *  

  * This library is distributed in the hope that it will be useful,

  * but WITHOUT ANY WARRANTY; without even the implied warranty of

  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

  * Lesser General Public License for more details.

  * 

  * You should have received a copy of the GNU Lesser General Public

  * License along with this library; if not, write to the Free Software

  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

  */

 package org.jaudiotagger.audio.mp3;

 import org.jaudiotagger.audio.generic.Utils;

 import org.jaudiotagger.tag.id3.valuepair.TextEncoding;

 import java.nio.ByteBuffer;

 /**

  * The first frame can sometimes contain a LAME frame at the end of the Xing frame

  * <p/>

  * <p>This useful to the library because it allows the encoder to be identified, full specification

  * can be found at http://gabriel.mp3-tech.org/mp3infotag.html

  * <p/>

  * Summarized here:

  * 4 bytes:LAME

  * 5 bytes:LAME Encoder Version

  * 1 bytes:VNR Method

  * 1 bytes:Lowpass filter value

  * 8 bytes:Replay Gain

  * 1 byte:Encoding Flags

  * 1 byte:minimal byte rate

  * 3 bytes:extra samples

  * 1 byte:Stereo Mode

  * 1 byte:MP3 Gain

  * 2 bytes:Surround Dound

  * 4 bytes:MusicLength

  * 2 bytes:Music CRC

  * 2 bytes:CRC Tag

  */

 public class LameFrame

 {

     public static final int LAME_HEADER_BUFFER_SIZE = 36;

     public static final int ENCODER_SIZE = 9;   //Includes LAME ID

     public static final int LAME_ID_SIZE = 4;

     public static final String LAME_ID = "LAME";

     private String encoder;

     /**

      * Initilise a Lame Mpeg Frame

      */

     private LameFrame(ByteBuffer lameHeader)

     {

         encoder = Utils.getString(lameHeader, 0, ENCODER_SIZE, TextEncoding.CHARSET_ISO_8859_1);

     }

     /**

      * Parse frame

      *

      * @return frame or null if not exists    

      */

     public static LameFrame parseLameFrame(ByteBuffer bb)

     {

         ByteBuffer lameHeader = bb.slice();

         String id = Utils.getString(lameHeader, 0, LAME_ID_SIZE, TextEncoding.CHARSET_ISO_8859_1);

         lameHeader.rewind();

         if (id.equals(LAME_ID))

         {

             LameFrame lameFrame = new LameFrame(lameHeader);

             return lameFrame;

         }

         return null;

     }

     /**

      * @return encoder

      */

     public String getEncoder()

     {

         return encoder;

     }

 }