Trouble with multiprocessing - python-3.x

Question

I am trying to save videos from multiple cameras connected to a Raspberry Pi using OpenCV. I have the Video saving working when there is a single camera without any multiprocessing. But when I try to have each camera on its own process nothing happens. I do not get any errors or log messages or anything, the process does not start.
Here is, what I think, the relevant code.
def init():
log(LOG_CODE_APP_START)
# video_capture(0) <-- works perfectly!
for index in range(0, 9):
camera_check = cv.VideoCapture(index)
if camera_check is None or not camera_check.isOpened():
continue
else:
camera_index.append(index)
print(camera_index) # <-- prints [0,1]
processes = []
for camera in camera_index:
video_process = multiprocessing.Process(name=str(camera), target=video_capture, kwargs={'camera': camera})
processes.append(video_process)
for process in processes:
print("Starting processes")
process.start()
def video_capture(camera=None):
start_time = time.time()
while True:
capture = cv.VideoCapture(camera)
capture.set(cv.CAP_PROP_FRAME_WIDTH, 800)
capture.set(cv.CAP_PROP_FRAME_HEIGHT, 600)
log(LOG_CODE_NEW_VIDEO)
file_name = 'camera_' + str(camera + 1) + '_' + '_' + get_time_string() + '_' + '.avi'
fourcc = cv.VideoWriter_fourcc(*'XVID')
height, width = get_video_stream_height_width(capture)
out = cv.VideoWriter(file_name, fourcc, 20.0, (width, height))
while int(time.time() - start_time) < CAPTURE_TIME:
ret, frame = capture.read()
if ret:
out.write(frame)
capture.release()
out.release()
start_time = time.time()
try:
if not os.path.exists(VIDEO_STORE):
os.mkdir(VIDEO_STORE)
shutil.move(file_name, VIDEO_STORE + '/' + file_name)
log(LOG_CODE_VIDEO_SAVED)
except Exception as e:
print("Exception")
log_error(e)

Answer 1

Change your script without multiprocessing to accept a camera number as a command-line argument.
Then try launching multiple instances of that script.