question: public Mp4BoxHeader ( String id ) { if ( id . length ( ) != IDENTIFIER_LENGTH ) { throw new RuntimeException ( "Invalid length:atom idenifier should always be 4 characters long" ) ; } dataBuffer = ByteBuffer . allocate ( HEADER_LENGTH ) ; try { this . id = id ; dataBuffer . put ( 4 , id . getBytes ( "ISO-8859-1" ) [ 0 ] ) ; dataBuffer . put ( 5 , id . getBytes ( "ISO-8859-1" ) [ 1 ] ) ; dataBuffer . put ( 6 , id . getBytes ( "ISO-8859-1" ) [ 2 ] ) ; dataBuffer . put ( 7 , id . getBytes ( "ISO-8859-1" ) [ 3 ] ) ; } catch ( UnsupportedEncodingException uee ) { throw new RuntimeException ( uee ) ; } }
target:  Construct header to allow manual creation of header for writing to file