Onboard Camera - V4L wrapper for use with OpenCV

Many people have been asking how to use the onbard camera (CSI and MIPI that comes with the Freesacale's development board) with OpenCV.

Unfortunately the mxc driver for this camera is not compatible with OpenCV and there is no way to use it directly, instead, we can use wrapper functions to access it. In this post I will share with you guys some utility functions I created (based on an Ipu demo app from Rogerio Pimentel - Freescaler) that uses V4L to access the camera.

When using these functions we will get frames on UYVY format (YUV422) and to use with OpenCV it must be converted to RGB24 (24bpp), all these are included in the source code.

The code can be downloaded from here, it also comes with a sample application, you just need to export the ROOTFS envioroment variable and check if the toolchain you are going to use is the same as defined in the Makefile, otherwise you must change it too.

The demo application (tested on i.MX6 sabresd board) performs the Canny edge detector and displays it using cvShowImage, you could display it directly in the framebuffer using the utility function, just uncomment the functions in the code and also add the conversion from RGB888toYUV422.

to run this application, make sure to have these drivers installed:

modprobe ov5642_camera
modprobe ov5640_camera_mipi
modprobe mxc_v4l2_capture

here is the result:

ps:  There is a "small" issue in these wrapper functions, as it uses multiple buffers for capturing and output (if you use it instead cvShowImage), you need to at least use the  V4LWrapper_QueryFrame function 3 times in a row to fill all buffers and the display it, so, the best scenario would be using this function like cvQueryFrame, when I got a fix for this I will update this post. Meanwhile just throw this function inside a loop function and you are good to go =)

EOF !