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[Bug 1518726] Re: Webcam cannot start after interrupted access with "VIDIOC_STREAMON: Invalid argument"

To: desktop-packages@xxxxxxxxxxxxxxxxxxx
From: Saren Taşçıyan <sarentasciyan@xxxxxxxxxxx>
Date: Sun, 22 Nov 2015 16:19:07 -0000
Reply-to: Bug 1518726 <1518726@xxxxxxxxxxxxxxxxxx>
Sender: bounces@xxxxxxxxxxxxx

** Description changed:

Hi,

I am trying to make my first application in C++ with OpenCV, where I am trying to capture images from the built-in webcam on my Lenovo T450s. I use Eclipse CDT as my IDE to write code and debug. During several trials, sometimes I need to STOP running applications via Eclipse (probably through some interrupt signal). Whenever the application is interrupted, during the next run it cannot access the webcam and is returning
"VIDIOC_STREAMON: Invalid argument"

Apparently this is because resources are not released due to the
interrupt. Also VLC cannot access webcam after I start seeing this
error.

Apparently there are 1-2 reports about this issue related to OpenCV and kernel, and there is also a workaround by handling SIGINT properly and correctly exiting. I could not work that solution in Eclipse, because probably Eclipse STOP button does not send SIGINT but some other signal. Nevertheless, I was expecting kernel to handle this in another way, so that resources would be released automatically to allow other applications to access webcam.
However, webcam cannot be accessed after a program is interrupted.

lsb_release -rd
Description: Ubuntu 14.04.3 LTS
Release: 14.04

uname -r
3.13.0-68-generic

References:
http://answers.opencv.org/question/28929/acquiring-video-from-webcam-problems/
http://askubuntu.com/questions/683327/libv4l2-error-turning-on-stream-invalid-argument-vidioc-streamon-invalid-argu
https://lawlorcode.wordpress.com/2014/04/08/opencv-fix-for-v4l-vidioc_s_crop-error/
http://ubuntuforums.org/showthread.php?t=2298140

Please don't hesitate to ask for more information about the issue and
correct me if my report isn't useful or sufficient.
+
+ Update: After further testing, I realized Eclipse is sending SIGTERM
+ signal, which if handled does not cause above mentioned issue. However,
+ a program may still crash or terminated without handling it properly.
+ This should not cause any issue for other applications.

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https://bugs.launchpad.net/bugs/1518726

Title:
Webcam cannot start after interrupted access with "VIDIOC_STREAMON:
Invalid argument"

Status in v4l-utils package in Ubuntu:
New

Bug description:
Hi,

Apparently this is because resources are not released due to the
interrupt. Also VLC cannot access webcam after I start seeing this
error.

lsb_release -rd
Description: Ubuntu 14.04.3 LTS
Release: 14.04

uname -r
3.13.0-68-generic

Please don't hesitate to ask for more information about the issue and
correct me if my report isn't useful or sufficient.

Update: After further testing, I realized Eclipse is sending SIGTERM
signal, which if handled does not cause above mentioned issue.
However, a program may still crash or terminated without handling it
properly. This should not cause any issue for other applications.

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