TkhdAtom.java

/**
 * 
 */
package mp4.util.atom;

/**
 * The header information for a single track.
 * 
 * In the absence of an edit list, the presentaiton of a track starts at the
 * beginning of the overall presentation.
 */
@SuppressWarnings("unused")
public class TkhdAtom extends LeafAtom {
  private static final int V0_CREATION_TIME_OFFSET = 4;
  private static final int V0_MODIFICATION_TIME_OFFSET = 8;
//  private static final int TRACK_ID_OFFSET = 12;
//  private static final int RESERVED_1_OFFSET = 16;
  private static final int V0_DURATION_OFFSET = 20;
  private static final int V1_DURATION_OFFSET = 28;  
//  private static final int RESERVED_2_OFFSET = 24;
//  private static final int LAYER_OFFSET = 32;
//  private static final int ALTERNATE_GROUP_OFFSET = 34;
//  private static final int VOLUME_OFFSET = 36;
//  private static final int RESERVED_3_OFFSET = 38;
//  private static final int MATRIX_OFFSET = 40;
//  private static final int WIDTH_OFFSET = 76;
//  private static final int HEIGHT_OFFSET = 80;
  
  public TkhdAtom() {
    super(new byte[]{'t','k','h','d'});
  }
  
  /**
   * Copy constructor
   * @param old the version to copy
   */
  public TkhdAtom(TkhdAtom old) {
    super(old);
  }
  
//  /**
//   * Get the track id.
//   * @return the track id
//   */
//  public long getTrackId() {
//    return data.getUnsignedInt(TRACK_ID_OFFSET);
//  }
//  
//  /**
//   * Set the track id
//   * @param id the new track id
//   */
//  public void setTrackId(long id) {
//    data.addUnsignedInt(TRACK_ID_OFFSET, id);
//  }
//    
  /**
   * Return the duration of the track.  The track duration is the sum of the 
   * sample durations (in the absence of an edit list).
   * @return the track's duration.
   */
  public long getDuration() {
	if (getVersion() == 0)
		return data.getUnsignedInt(V0_DURATION_OFFSET);
	else
		return data.getLong(V1_DURATION_OFFSET);		
  }
  
  /**
   * Set the duration for the track.  The track duration is the sum of the sample
   * durations (in the absence of an edit list).  The timescale is from the movie header atom.
   * @param duration the track's duration in movie's timescale
   */
  public void setDuration(long duration) {
    if (getVersion() == 0)
	  data.addUnsignedInt(V0_DURATION_OFFSET, duration);
    else
	  data.addLong(V1_DURATION_OFFSET, duration);
    
  }
  
  /**
   * Cut the tkhd atom at the specified time.  The duration for the track header is set
   * to zero initially.  It must be filled in later.
   */
  public TkhdAtom cut() {
    TkhdAtom cutTkhd = new TkhdAtom(this);
    cutTkhd.setDuration(0);
    return cutTkhd;
  }
  
  @Override
  public void accept(AtomVisitor v) throws AtomException {
    v.visit(this); 
  }
	public boolean force32BitTimes() {
		if (getVersion() == 0)
			return false;
		data.collapse64To32(V0_CREATION_TIME_OFFSET);
		data.collapse64To32(V0_MODIFICATION_TIME_OFFSET);
		data.collapse64To32(V0_DURATION_OFFSET);
		setVersion((byte)0);
		return true;
	}

}