(python 3)从.h264自动转换为.mp4

我有一个Python 3代码,应该用来录制视频。不幸的是,我不希望它出现在.h264中,我需要将其转换为.mp4。使用其他StackOverflow线程作为模板(特别是 this 一),我认为最简单的方法是使用 subprocess.Popen 插入 MP4Box -add filename.h264 filename.mp4 进入终端,让它自动为我做这件事。不幸的是,Python脚本没有做任何事情,我也没有收到任何错误消息,所以我不知道出了什么问题。h264文件会出现在我想要的文件夹中,如果我手动将命令放入终端,会出现.mp4,但当我让它运行时,什么也没有发生。剧本的其余部分很有魅力。代码如下:

#!/usr/bin/python

from gpiozero import MotionSensor
from gpiozero import Motor
from picamera import PiCamera
import subprocess
import os.path
import shlex
import datetime as dt
from time import sleep

camera = PiCamera()
pir = MotionSensor(4, 1, 100, .6, False)
motor = Motor(3,14) #first number is forwards, second is backwards
startupTime = 1
recordingTime = 1
collectionTime = 3
resetTime = 30



while True:
    sleep(startupTime) #delay a bit so installation can take place

    #wait for motion, then move the motor back and forth
    pir.wait_for_motion() 
    print("Motion Detected")
    #moves motor forward for 3 seconds at 25% speed
    motor.forward(.25)
    print("Strip Extending")
    sleep(3) 
    motor.stop()
    #leaves strip out for given amount of time
    print("Collecting Sample")
    sleep(collectionTime) 
    #moves motor backward for 3 seconds at 50% speed
    motor.backward(.5)
    print("Strip Retracting")
    sleep(3) 
    motor.stop()

    #Prep file for correct saving
    filename = dt.datetime.now().strftime("%Y-%m-%d_%H.%M.%S.h264") #saves file as a date
    save_path= "/home/pi/ANALYSIS"
    completed_video= os.path.join(save_path, filename)

    #Start recording
    camera.start_recording(completed_video) #starts recording and saves it as filename
    print("Camera Recording")
    camera.annotate_text = dt.datetime . now() . strftime("%Y-%m-%d_%H.%M.%S")
    start=dt.datetime.now()

    #Keep recording until time runs out, annotate to make sure we have reference frame
    while (dt.datetime.now() - start).seconds < recordingTime: 
        camera.annotate_text = dt.datetime.now(). strftime("%Y-%m-%d_%H.%M.%S")
        camera.wait_recording(.2)
    camera.stop_recording()

    #Conversion to usable file format
    print("Camera finished recording... Beginning Analysis")
    from subprocess import CalledProcessError
    command = shlex.split("MP4Box -add {} {}.mp4".format(completed_video, os.path.splitext(filename)[0]))
    try:
        output = subprocess.check_output(command, stderr=subprocess.STDOUT, shell=True)
    except CalledProcessError as e:
        print('FAIL:\ncmd:{}\noutput:{}'.format(e.cmd, e.output))

    #starts detecting again after given time
    sleep(resetTime)
    print("Ready for next sample")

>Traceback (most recent call last):  
>
    File "/home/pi/Detector.py", line 62, in <module> output = 
      subprocess.check_output(command, stderr=subprocess.STDOUT) 
    File "/usr/lib/python3.4/subprocess.py", line 620, in check_output raise 
      CalledProcessError(retcode, process.args, output=output) 
      subprocess.CalledProcessError: 
        Command '['MP4Box', '-add', '2017-07-11_15.34.49.h264.h264', '2017-07-11_15.34.49.h264.mp4']' 
>
Returned non-zero exit status 1"