java获取网络音频时长--不是很准

import javazoom.jl.decoder.Bitstream;
import javazoom.jl.decoder.Header;

public static void main(String[] args) {
        try {
            long startTime=System.currentTimeMillis();   //获取开始时间
            URL urlfile = new URL("http://resource.puxinwangxiao.com/b4ef18fe62948ab2528127c8c1357ddd.mp3");
            //File file = new File("C:\\music\\test2.mp3");
            //URL urlfile = file.toURI().toURL();
            URLConnection con = urlfile.openConnection();
            int b = con.getContentLength();// 得到音乐文件的总长度
            BufferedInputStream bis = new BufferedInputStream(con.getInputStream());
            Bitstream bt = new Bitstream(bis);
            Header h = bt.readFrame();
            int time = (int) h.total_ms(b);
            System.out.println(time / 1000);
            long endTime1=System.currentTimeMillis(); //获取结束时间
            System.out.println("所需时间： "+(endTime1-startTime)+"ms");
        }catch (Exception e ){
            System.out.println(e.getMessage());
        }
    }