can't open camera by index

[richierh]

I use zbarcam which has dependencies on opencv
why I got this error ?

[INFO   ] [Camera      ] Provider: opencv(['camera_picamera', 'camera_gi'] ignored)
[ WARN:0] global /tmp/pip-req-build-ms668fyv/opencv/modules/videoio/src/cap_v4l.cpp (893) open VIDEOIO(V4L2:/dev/video0): can't open camera by index
 Traceback (most recent call last):
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/lang/builder.py", line 705, in _apply_rule
     setattr(widget_set, key, value)
   File "kivy/weakproxy.pyx", line 35, in kivy.weakproxy.WeakProxy.__setattr__
   File "kivy/properties.pyx", line 498, in kivy.properties.Property.__set__
   File "kivy/properties.pyx", line 840, in kivy.properties.ListProperty.set
   File "kivy/properties.pyx", line 545, in kivy.properties.Property.set
   File "kivy/properties.pyx", line 600, in kivy.properties.Property.dispatch
   File "kivy/_event.pyx", line 1248, in kivy._event.EventObservers.dispatch
   File "kivy/_event.pyx", line 1154, in kivy._event.EventObservers._dispatch
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy_garden/xcamera/xcamera.py", line 85, in _on_index
     self._on_index_dispatch(*largs)
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy_garden/xcamera/xcamera.py", line 88, in _on_index_dispatch
     super()._on_index(*largs)
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/uix/camera.py", line 103, in _on_index
     self._camera = CoreCamera(index=self.index,
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/core/camera/camera_opencv.py", line 70, in __init__
     super(CameraOpenCV, self).__init__(**kwargs)
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/core/camera/__init__.py", line 70, in __init__
     self.init_camera()
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/core/camera/camera_opencv.py", line 120, in init_camera
     self._resolution = (int(frame.shape[1]), int(frame.shape[0]))
 AttributeError: 'NoneType' object has no attribute 'shape'
 
 During handling of the above exception, another exception occurred:
 
 Traceback (most recent call last):
   File "main.py", line 48, in <module>
     DemoApp().run()
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/app.py", line 949, in run
     self._run_prepare()
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/app.py", line 918, in _run_prepare
     self.load_kv(filename=self.kv_file)
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/app.py", line 691, in load_kv
     root = Builder.load_file(rfilename)
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/lang/builder.py", line 306, in load_file
     return self.load_string(data, **kwargs)
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/lang/builder.py", line 408, in load_string
     self._apply_rule(
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/lang/builder.py", line 663, in _apply_rule
     self._apply_rule(
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/lang/builder.py", line 663, in _apply_rule
     self._apply_rule(
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/lang/builder.py", line 663, in _apply_rule
     self._apply_rule(
   [Previous line repeated 3 more times]
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/lang/builder.py", line 661, in _apply_rule
     child.apply_class_lang_rules(
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/uix/widget.py", line 463, in apply_class_lang_rules
     Builder.apply(
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/lang/builder.py", line 541, in apply
     self._apply_rule(
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/lang/builder.py", line 663, in _apply_rule
     self._apply_rule(
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/lang/builder.py", line 661, in _apply_rule
     child.apply_class_lang_rules(
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/uix/widget.py", line 463, in apply_class_lang_rules
     Builder.apply(
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/lang/builder.py", line 541, in apply
     self._apply_rule(
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/lang/builder.py", line 710, in _apply_rule
     raise BuilderException(rule.ctx, rule.line,
 kivy.lang.builder.BuilderException: Parser: File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy_garden/xcamera/xcamera.kv", line 27:
 ...
      25:
      26:    id: camera
 >>   27:    resolution: 640, 480 # 1920, 1080
      28:    allow_stretch: True
      29:
 ...
 AttributeError: 'NoneType' object has no attribute 'shape'
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/lang/builder.py", line 705, in _apply_rule
     setattr(widget_set, key, value)
   File "kivy/weakproxy.pyx", line 35, in kivy.weakproxy.WeakProxy.__setattr__
   File "kivy/properties.pyx", line 498, in kivy.properties.Property.__set__
   File "kivy/properties.pyx", line 840, in kivy.properties.ListProperty.set
   File "kivy/properties.pyx", line 545, in kivy.properties.Property.set
   File "kivy/properties.pyx", line 600, in kivy.properties.Property.dispatch
   File "kivy/_event.pyx", line 1248, in kivy._event.EventObservers.dispatch
   File "kivy/_event.pyx", line 1154, in kivy._event.EventObservers._dispatch
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy_garden/xcamera/xcamera.py", line 85, in _on_index
     self._on_index_dispatch(*largs)
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy_garden/xcamera/xcamera.py", line 88, in _on_index_dispatch
     super()._on_index(*largs)
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/uix/camera.py", line 103, in _on_index
     self._camera = CoreCamera(index=self.index,
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/core/camera/camera_opencv.py", line 70, in __init__
     super(CameraOpenCV, self).__init__(**kwargs)
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/core/camera/__init__.py", line 70, in __init__
     self.init_camera()
   File "/home/cireng/.virtualenvs/kivypos/lib/python3.8/site-packages/kivy/core/camera/camera_opencv.py", line 120, in init_camera
     self._resolution = (int(frame.shape[1]), int(frame.shape[0]))
 

[furas]

What system do you use?
It seems you use some Linux but what distribution and version.

Error shows open VIDEOIO(V4L2:/dev/video0): can't open camera by index.
Do you have /dev/video0 in your system?

ls /dev/video*

Did you test your camera directly with opencv?

import cv2

cap = cv2.VideoCapture('/dev/video0')
ret, frame = cap.read()
print(ret, frame)

If you have /dev/video0 and this code doesn't work then you can try with sudo because you may not have privileges.

sudo python script.py

If this code work then problem can be in zbarcam and you would have to ask on zbarcam forum/repo

---

I tested this code on Linux Mint 20 based on Ubuntu 20.04 and it works without problem.
I don't have your code with zbarcam to test it.

[oqlaalrefai]

@furas I try the opencv test and I get this result:
False None
and when try the sudo command Iget this
can't open file 'script.py': [Errno 2] No such file or directory

[furas]

@oqlaalrefai

If sudo can't find file then you may have to use /full/path/to/script.py

False None means it couldn't find camera - and it needs different value in VideoCapture(..). OR camera may need some time to warm up before it start sending images - it may need to use time.sleep(...) before read()