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

Bug #1518726 reported by Saren Taşçıyan on 2015-11-22
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
v4l-utils (Ubuntu)
Undecided
Unassigned

Bug Description

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.

affects: xawtv (Ubuntu) → v4l-utils (Ubuntu)
description: updated
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