OpenCV: can't set resolution of video capture

Question

I am using OpenCV 2.4.5 on Ubuntu 12.04 64-bit. I would like to be able to set the resolution of the input from my Logitech C310 webcam. The camera supports up to 1280x960 a

Answer 1

This is a bug in the v4l "version" (build) of OpenCV 2.4 (including 2.4.12), but the bug is not in the libv4l version. For OpenCV 3.1.0, neither the v4l nor the libv4l version has the bug.

(Your error error message HIGHGUI ERROR: V4L/V4L2: VIDIOC_S_CROP indicates that you have the v4l version; the message is in cap_v4l.cpp, see code, but not in cap_libv4l.cpp.)

A workaround to get the v4l version of OpenCV 2.4 to work at a fixed resolution other than 640x480 is changing the values for DEFAULT_V4L_WIDTH and DEFAULT_V4L_HEIGHT in modules/highgui/src/cap_v4l.cpp and re-building OpenCV, kudos to this answer.

If you want to build the libv4l version instead, all you likely need to do is install libv4l-dev and rebuild OpenCV; WITH_LIBV4L was enabled by default for me. If it is not, your cmake command should contain

-D WITH_LIBV4L=ON

The cmake output (or version_string.tmp) for a libv4l build contains something like

  Video I/O:
    ...
    V4L/V4L2:   Using libv4l1 (ver 0.8.6) / libv4l2 (ver 0.8.6)

(For a v4l build, it is just V4L/V4L2: NO/YES.)