Video4Linux2 C++ simple wrapper
Intro
A simple C++ header library to capture frames from a usb camera into a callback function for image processing.
How to use
Run a simple hello camera to see how easy. no more v4l2 boilrplate code.
// callback function to pipe out image to stdout
// later pipe to ffplay to display image
void callback_stdout_pipe(uint8_t *p_data, size_t len) {
uint8_t outBuff[921600];
util_v4l2::raw_to_rgb(p_data, 0, outBuff, 921600, 640 * 480, 8);
fwrite(outBuff, 640*480*3, 1, stdout);
}
int main() {
// a capture instance
// device, resolution, pixel format , and callback function this should be known in advance you can use
// v4l2-ctl command to figure that out.
capture cap("/dev/video0", 640,480,pixel_format ::V4L2CXX_PIX_FMT_YUYV,callback_stdout_pipe);
// start streaming - a blocking function.
cap.run();
}Examples
- TODO ; cmake; See example folder
v4l2 Extension unit
- TODO
- TODO example with LI-USB30-V034M
pipe to ffplay
./libv4l2cxx | ffplay -f rawvideo -i pipe:0 -video_size 640x480 -pixel_format rgb24 -framerate 60
ffmpeg commands
Play video device
ffplay -f v4l2 -i /dev/video0 -video_size 640x480 -pixel_format yuyv422 -framerate 30
ffplay -f v4l2 -i /dev/video0 -video_size 640x480 -pixel_format mjpeg
ffplay -f v4l2 -i /dev/video0 -video_size 1280x720 -pixel_format mjpeg -framerate 30
Pipe libv4l2 to ffplay, tell ffplay to use input (-i pipe:0 = stdin standrd input)
./libv4l2cxx | ffplay -f rawvideo -i pipe:0 -video_size 640x480 -pixel_format rgb24 -framerate 60
List formats for device
v4l2-ctl --list-formats
List exdtended formats including resolution info for device
v4l2-ctl --list-formats-ext
v4l2-ctl -L
List controls for device
v4l2-ctl --all
Change control option to value
v4l2-ctl -c \
v4l2-ctl -d /dev/video1 -c exposure_absolute=100