Hello:
I'm writing a code wich uses an USB webcam. Enviroment: Ubuntu 12.04 + OpenCV 2.4.2. All the development libraries are installed and updated (FFMPEG, V4L and so on).
Since CPU usage and bandwitdh are critical, I need to set some parameters, such as the frame size:
VideoCapture MyWebCamVariable;
MyWebCamVariable.open(0);
MyWebCamVariable.set(CV_CAP_PROP_FRAME_WIDTH, 320)
MyWebCamVariable.set(CV_CAP_PROP_FRAME_HEIGHT, 240)
Ok, everything works flawlessly, camera is shown properly. Troubles appear when dealing with parameters such as CV_CAP_PROP_FOURCC or CV_CAP_PROP_FPS (all of them are documented in the OpenCV reference manual).
For example:
char MyWebCamCodec;
MyWebCamCodec = MyWebCamVariable.get(CV_CAP_PROP_FOURCC);
gives the following message when executed:
HIGHGUI ERROR: V4L2: Unable to get property <unknown property string>(6) - Invalid Argument
Notice that I used get instruction, so no chances to mistake with a bad value. The rest of the code works well. Variable MyWebCamCodec is given an unrecognised character: �
In a Linux terminal I used v4l2-ctl --list-formats-ext and I checked that lots of capture modes (resolutions, FPS, YUV and MJPEG) are avaiable.
Regards