public static int doWaitFor(Process process) {
  InputStream in = null;
  InputStream err = null;
  int exitValue = -1; // returned to caller when p is finished
  try {
    in = process.getInputStream();
    err = process.getErrorStream();
    boolean finished = false; // Set to true when p is finished
    while (!finished) {
      try {
        while (in.available() > 0) {
          // Print the output of our system call
          Character c = new Character((char) in.read());
          System.out.print(c);
        while (err.available() > 0) {
          // Print the output of our system call
          Character c = new Character((char) err.read());
          System.out.print(c);
        // Ask the process for its exitValue. If the process
        // is not finished, an IllegalThreadStateException
        // is thrown. If it is finished, we fall through and
        // the variable finished is set to true.
        exitValue = process.exitValue();
        finished = true;
      } catch (IllegalThreadStateException e) {
        // Process is not finished yet;
        // Sleep a little to save on CPU cycles
        Thread.currentThread().sleep(500);
  } catch (Exception e) {
    e.printStackTrace();
  } finally {
    try {
      if (in != null) {
        in.close();
    } catch (IOException e) {
      e.printStackTrace();
    if (err != null) {
      try {
        err.close();
      } catch (IOException e) {
        e.printStackTrace();
  return exitValue;
Java调用外部命令使用 Runtime.getRuntime().exec(command) 。
在使用调用ffmpeg命令时，必须要读取执行命令输出流中的内容，程序才不会阻塞。否则缓冲读满后，进程会卡住。
视频转换会非常耗时，取决于硬件性能。在实际应用中，我们也可以开启线程去处理。
FFmpeg还提供C调用，公共库集成。以上方法并不是最优解决方案，仅提供一种参考。