树莓派usb摄像头用fswebcam 设置

树莓派上可以找到摄像头驱动，但是在树莓派终端输入raspistill -o image.jpg，输出如下错误：

mmal: Cannot read camera info, keeping the defaults for OV5647
mmal: mmal_vc_component_create: failed to create component 'vc.ril.camera' (1:ENOMEM)
mmal: mmal_component_create_core: could not create component 'vc.ril.camera' (1)
mmal: Failed to create camera component
mmal: main: Failed to create camera component
mmal: Camera is not detected. Please check carefully the camera module is installed correctly

其原因为使用的摄像头为USB摄像头，而raspistill命令只能用于CSI摄像头。对于USB接口的摄像头，可以通过调用fswebcam进行访问。
在树莓派终端输入sudo apt-get install fswebcam安装fswebcam。通过输入sudo fswebcam image.jpg进行拍照测试。使用方法可以通过输入fswebcam -h查询。