v4l2_fract
struct v4l2_fract min; /* Minimum frame interval [s] */
struct v4l2_fract max; /* Maximum frame interval [s] */
struct v4l2_fract step; /* Frame interval step size [s] */
struct v4l2_fract discrete;
struct v4l2_fract timeperframe; /* Time per frame in seconds */
struct v4l2_fract timeperframe; /* Time per frame in seconds */
struct v4l2_fract pixelaspect;
struct v4l2_fract frameperiod; /* Frames, not fields */
struct v4l2_fract picture_aspect;