How to solve TypeError: cannot pickle 'cv2.VideoWriter' object?

Question

When I try to use cv2.VideoWriter with multiproccesing, I get an error (shown below). How do I fix this?

from .audio import Audio
from .video import Video
from uuid import uuid1
from os import mkdir,listdir
from multiprocessing import Process
import ffmpeg
class Recorder(Video,Audio):
    def __init__(self):
        unique_id = uuid1()
        self.unique_id = unique_id
        directory = listdir(".")
        if "tmp" not in directory:
            mkdir("tmp")
        Video.__init__(self,self.unique_id)
        Audio.__init__(self,self.unique_id)
    
    def record_screen(self):
        video = Process(target = self._record_video)
        video.start()
        audio = Process(target = self._record_audio)
        audio.start()

    def _combine_audio_and_video(self,path):
        video = ffmpeg.input(f'./tmp/{self.unique_id}/video.avi')
        audio = ffmpeg.input(f'./tmp/{self.unique_id}/output.wav')
        out = ffmpeg.output(video, audio, path, vcodec='copy', acodec='aac', strict='experimental')
        out.run()

    def stop(self):
        stop_video = Process(target = self.stop_video)
        stop_video.start()
        stop_audio = Process(target = self.stop_audio)
        stop_audio.start()
        
    def save(self,path):
        print("Saving....")
        self._combine_audio_and_video(path)
        print("FILE SAVED")

The error is

Traceback (most recent call last):
  File "e:\SCREEN RECORDER WITH PY\ok.py", line 5, in <module>
    ok.record_screen()
  File "e:\SCREEN RECORDER WITH PY\screen_recorder\recorder.py", line 19, in record_screen
    video.start()
  File "C:\Users\krish\AppData\Local\Programs\Python\Python38\lib\multiprocessing\process.py", line 121, in start
    self._popen = self._Popen(self)
  File "C:\Users\krish\AppData\Local\Programs\Python\Python38\lib\multiprocessing\context.py", line 224, in _Popen
    return _default_context.get_context().Process._Popen(process_obj)
  File "C:\Users\krish\AppData\Local\Programs\Python\Python38\lib\multiprocessing\context.py", line 327, in _Popen
    return Popen(process_obj)
  File "C:\Users\krish\AppData\Local\Programs\Python\Python38\lib\multiprocessing\popen_spawn_win32.py", line 93, in __init__
    reduction.dump(process_obj, to_child)
  File "C:\Users\krish\AppData\Local\Programs\Python\Python38\lib\multiprocessing\reduction.py", line 60, in dump
    ForkingPickler(file, protocol).dump(obj)
TypeError: cannot pickle 'cv2.VideoWriter' object

score 0 · Answer 1 · answered Mar 07 '21 at 10:15

0

Processes can only return and receive picklable values. Consider using threading instead, also refer to this question. There are some differences between threads and processes as explained here

answered Mar 07 '21 at 10:15

Kenivia

384
1
13

How to solve TypeError: cannot pickle 'cv2.VideoWriter' object?

1 Answers1