question: @ Override public AudioInputStream synthesize ( int backchannelNumber , AudioFileFormat aft ) throws SynthesisException { int numberOfBackChannels = unitFileReader . getNumberOfUnits ( ) ; if ( backchannelNumber >= numberOfBackChannels ) { throw new IllegalArgumentException ( "This voice has " + numberOfBackChannels + " backchannels only. so it doesn't support unit number " + backchannelNumber ) ; } VocalizationUnit bUnit = unitFileReader . getUnit ( backchannelNumber ) ; long start = bUnit . startTime ; int duration = bUnit . duration ; Datagram [ ] frames = null ; try { frames = audioTimeline . getDatagrams ( start , duration ) ; } catch ( IOException e ) { throw new SynthesisException ( "Can not read data from timeline file " + e ) ; } LinkedList < Datagram > datagrams = new LinkedList < Datagram > ( ) ; datagrams . addAll ( Arrays . asList ( frames ) ) ; DoubleDataSource audioSource = new DatagramDoubleDataSource ( datagrams ) ; return ( new DDSAudioInputStream ( new BufferedDoubleDataSource ( audioSource ) , aft . getFormat ( ) ) ) ; }
target:  Synthesize given vocalization (i.e. unit-selection)