Describe the doc issue

Hello,

I think this is documentation issue + bug issue

First, when reading a video, this warning occured, giving me a None value instead of a frame :

[ WARN:[email protected]] global cap_ffmpeg_impl.hpp:1541 grabFrame packet read max attempts exceeded, if your video have multiple streams (video, audio) try to increase attempt limit by setting environment variable OPENCV_FFMPEG_READ_ATTEMPTS (current value is 4096)

I wanted to create the environment variable inside my Python file to be machine-independant so I followed the instructions in page OpenCV: OpenCV environment variables reference

When I executed this code in the given page :

import os
os.environ["MY_ENV_VARIABLE"] = True
import cv2 # variables set after this may not have effect

It raised this error :

Traceback (most recent call last):
  File "C:\Users\...\script.py", line 2, in <module>
    os.environ["MY_ENV_VARIABLE"] = True
  File "C:\ProgramData\miniconda\new_torch\lib\os.py", line 684, in __setitem__
    value = self.encodevalue(value)
  File "C:\ProgramData\miniconda\new_torch\lib\os.py", line 742, in check_str
    raise TypeError("str expected, not %s" % type(value).__name__)
TypeError: str expected, not bool

Same error if I give an int instead of a bool.
So I tried giving a str instead, to the variable :

import os
os.environ["OPENCV_FFMPEG_READ_ATTEMPTS"] = str(16000)
import cv2 # variables set after this may not have effect
print(os.environ["OPENCV_FFMPEG_READ_ATTEMPTS"])

This prints me 16000, but I still have the first error provided at the top, saying that current value of OPENCV_FFMPEG_READ_ATTEMPTS is 4096, when reading a particular frame of a particular video.

Now that I have created a system environment variable in Windows, plus restarted my computer, it works.

Do anyone know what the opencv Doc is missing and why setting environment variable inside python file seems impossible ?

(Windows 10, opencv-python 4.9.0.80, Python 3.9.12, openCV doc tried on version 4.10.0 and 4.9.0)

Fix suggestion

No response