Java 获取amr音频格式的音频长度

import java.io.File;

import java.io.IOException;

import java.io.RandomAccessFile;



public class GetAmrDuration {



    /**

     * 得到amr的时长

     * 

     * @param file

     * @return

     * @throws IOException

     */

    public static int getAmrDuration(File file) throws IOException {

        long duration = -1;

        int[] packedSize = { 12, 13, 15, 17, 19, 20, 26, 31, 5, 0, 0, 0, 0, 0,

                0, 0 };

        RandomAccessFile randomAccessFile = null;

        try {

            randomAccessFile = new RandomAccessFile(file, "rw");

            long length = file.length();// 文件的长度

            int pos = 6;// 设置初始位置

            int frameCount = 0;// 初始帧数

            int packedPos = -1;



            byte[] datas = new byte[1];// 初始数据值

            while (pos <= length) {

                randomAccessFile.seek(pos);

                if (randomAccessFile.read(datas, 0, 1) != 1) {

                    duration = length > 0 ? ((length - 6) / 650) : 0;

                    break;

                }

                packedPos = (datas[0] >> 3) & 0x0F;

                pos += packedSize[packedPos] + 1;

                frameCount++;

            }



            duration += frameCount * 20;// 帧数*20

        } finally {

            if (randomAccessFile != null) {

                randomAccessFile.close();

            }

        }

        return (int)((duration/1000)+1);

    }

    

    public static void main(String[] args) throws IOException {

        File source = new File("6.amr");

        System.out.println(getAmrDuration(source));

    }



}