java使用mencoder转码视频为什么失败？

在linux中敲入命令

mencoder 1.rmvb -o 2.avi -vf scale=320:240 -oac pcm -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=500

能够转码成功

这是java代码

  String toAvi = "mencoder "
    + originPath
    + "-o "
    + aviPath
    + "-vf scale=320:240 -oac pcm -ovc lavc -lavcopts vcodec=mpeg4:vbitrate=500";
  try {
   // Process p = Runtime.getRuntime().exec(toAvi);
   Runtime rt = Runtime.getRuntime();
   Process proc = rt.exec(toAvi);
   InputStream is = proc.getInputStream();
   final BufferedReader stdout = new BufferedReader(
     new InputStreamReader(is));
   is = proc.getErrorStream();
   final BufferedReader stderr = new BufferedReader(
     new InputStreamReader(is));
   final Vector outputLines = new Vector();
   // this deals with the output from the process in it's own thread
   Thread stdoutThread = new Thread() {
    public void run() {
     try {
      PrintWriter writer = new PrintWriter(new FileWriter(
        "log.txt"));
      int l;
      String line;
      for (l = 0; (line = stdout.readLine()) != null;) {
       if (line.length() > 0) {
        l++;
        outputLines.appendElement(line);
        // if (line.matches("Starting playback..."))
       }

      }
      System.out.println("\nRead " + l
        + " lines from stdout.");
      stdout.close();
      writer.close();
     } catch (IOException ie) {
      System.out.println("IO exception on stdout: " + ie);
     }
    }
   };
   stdoutThread.start();

   Thread stderrThread = new Thread() {
    public void run() {
     try {
      int l;
      String line;
      for (l = 0; (line = stderr.readLine()) != null;) {
       if (line.length() > 0)
        l++;
       System.out.print(",");
      }
      System.out.println("\nRead " + l
        + " lines from stderr.");
      stderr.close();
     } catch (IOException ie) {
      System.out.println("IO exception on stderr: " + ie);
     }
    }
   };
   stderrThread.start();

   System.out.println("About to waitfor");
   try {
    int exitVal = proc.waitFor();
   } catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
   }
   System.out.println("Done.");

  } catch (IOException e) {
   e.printStackTrace();
   System.out.println("Exec failed. Exiting");
   System.exit(0);
   return false;
  }

  return true;

执行后，linux输出

[2015-03-03 11:14:20] [INFO] [System.out] [creat folder:/app/tongweb02/deployment/modules/cms-web/static/upload/video/origin/2015/03/03/1.rmvb]
[2015-03-03 11:14:20] [INFO] [System.out] [creat folder:/app/tongweb02/deployment/modules/cms-web/static/upload/video/flv/2015/03/03/1425352460609.flv]
[2015-03-03 11:14:20] [INFO] [System.out] [creat folder:/app/tongweb02/deployment/modules/cms-web/static/upload/video/videoTemp]
[2015-03-03 11:14:20] [INFO] [System.out] [originVideo:/app/tongweb02/deployment/modules/cms-web/static/upload/video/origin/2015/03/03/1.rmvb]
[2015-03-03 11:14:20] [INFO] [System.out] [transform video:/app/tongweb02/deployment/modules/cms-web/static/upload/video/videoTemp/1425352460776.avi]
[2015-03-03 11:14:20] [INFO] [System.out] [About to waitfor]
[2015-03-03 11:14:20] [INFO] [System.out] [
Read 0 lines from stderr.]
[2015-03-03 11:14:20] [INFO] [System.out] [
Read 2 lines from stdout.]
[2015-03-03 11:14:20] [INFO] [System.out] [Done.]
[2015-03-03 11:14:20] [INFO] [System.out] [rmvb to avi true]

并没有成功转码，在文件夹中没有视频文件，求一段java转码代码，使用mencoder的