将m4s文件转为mp4

使用ffmpeg可以从m4s音频和视频文件生成mp4文件，命令为

ffmpeg -i audio.m4s -i video.m4s -codec copy 1.mp4

java提供Process类来模拟执行命令行。
需要在项目资源路径下放置ffmpeg.exe

package com.client.util;


import com.client.spider.w12.bilibili.core.Progress;
import com.client.spider.w12.bilibili.exception.FileUnexpectedEndException;

import java.io.*;
import java.util.Arrays;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/** 从m4s音频和视频文件生成mp4<br/>
 * 使用ffmpeg命令进行,命令为<br/>
 * ffmpeg -i audio.m4s -i video.m4s -codec copy 1.mp4<br/>
 * 需要在项目资源路径下放置ffmpeg.exe
 */
public class TransCoding {
    /**如果文件存在，删除文件*/
    public static void deleteIfExist(String pathname){
        File file=new File(pathname);
        if(file.exists()){
            file.delete();
        }
    }
    public static boolean checkExist(String pathname){
        File file=new File(pathname);
        return file.exists();
    }
    //ffmpeg程序的位置
    private static String ffmpeg="\\ffmpeg.exe";;
    public void createMp4FromM4s(String audioPath,String videoPath,String output){
        if(!checkExist(audioPath)|| !checkExist(videoPath))throw new RuntimeException("输入文件不存在");
        deleteIfExist(output);
        System.out.println("生成文件中 "+output);
        String command=ffmpeg+" -i "+audioPath+" -i "+videoPath+" -codec copy "+output;
        exec(Arrays.asList(command.split(" ")));
    }
    public void createMp4FromM4sInNewThread(String audioPath,String videoPath,String output,Runnable additionTask){
        new Thread(()->{
            createMp4FromM4s(audioPath, videoPath, output);
            if(additionTask!=null)additionTask.run();
        }).start();
    }
    /**
     * 模拟命令行执行命令
     * @param command   命令
     * @return  true-成功 false-失败
     */
    private boolean exec(List<String> command){
        ProcessBuilder processBuilder = new ProcessBuilder();
        processBuilder.command(command);
        try {
             processBuilder.redirectErrorStream(true);
            Process process = processBuilder.start();
            new StreamHandler(process.getInputStream()).start();
            process.waitFor();
            process.destroy();
        } catch (IOException e) {
            e.printStackTrace();
            return false;
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return true;
    }
    //读取输出，防止阻塞
    static class StreamHandler extends Thread {

        private InputStream in;

        public StreamHandler(InputStream in) {
            this.in = in;
        }

        public void run() {
            try {
                BufferedReader reader = new BufferedReader(new InputStreamReader(in));
                String line;
                while ((line = reader.readLine()) != null) {
                    //System.out.println(Thread.currentThread().getName() + "\t" + line);
                }
            } catch (Exception e) {
                System.out.println(Thread.currentThread().getName() + "\t" + e.getMessage());
            }
        }
    }
    public static void main(String[] args) {
        String v="D:\\magnetCatcher\\test\\BV1HZ4y117zQ\\Video.m4s";
        String a="D:\\magnetCatcher\\test\\BV1HZ4y117zQ\\Audio.m4s";
        String o="D:\\magnetCatcher\\test\\BV1HZ4y117zQ\\Video.mp4";
        new TransCoding().createMp4FromM4s(a,v,o);
    }
}

经测试,该类可以转化B站的缓存视频。对于几十兆大小的视频，转化时间在秒级内。