libv4l capturing backend spams stderr with "HIGHGUI ERROR: V4L2:..." (Bug #3004)

Added by Hans Meine almost 12 years ago. Updated over 9 years ago.

Status:Open Start date:2013-05-03
Priority:Normal Due date:
Assignee:Vadim Pisarevsky % Done:

0%
Category:highgui-camera
Target version:-
Affected version:branch 'master' (2.4.9) Operating System:
Difficulty: HW Platform:
Pull request:

Description

I have tried querying various properties from the capturing backend, but the libv4l backend defeats this by writing errors to stderr every time I try to access unsupported properties.

AFAICS, unsupported properties should be ignored (that is, setProperty returns false, but unfortunately, getProperty cannot do so ATM). If I want to write a backend-independent client software, it is undesirable to get lots of errors on specific backends, no?

Even better would be to have a way to query (un)supported properties, e.g. by passing an optional bool* to getProperty, and let it write a success flag to that pointer if it is non-NULL.

Finally, I wonder whether these "ERROR"s fprintf's should have been CV_WARN()s like e.g. in cap_gstreamer.cpp.

History

#1
Updated by Hans Meine almost 12 years ago

BTW, I forgot to mention that issue #1984 seems to be slightly related, but I think it is more about a specific instance of this problem.

#2
Updated by Anna Kogan almost 12 years ago

Hello Hans,
Thank you for reporting the issue. If you can solve the issue on your side, a pull request in our GitHub repo would be highly appreciated!

  • Assignee changed from Vadim Pisarevsky to Hans Meine

#3
Updated by Hans Meine almost 12 years ago

Hi Anna, does your comment imply that my thoughts are acknowledged? I don't want to spend time on this if you don't agree.

#4
Updated by Anna Kogan almost 12 years ago

  • Assignee changed from Hans Meine to Vadim Pisarevsky

#5
Updated by Maksim Shabunin over 9 years ago

Issue has been transferred to GitHub: https://github.com/Itseez/opencv/issues/4561

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