ref: dd0fde6262de2b1be2d49a6414c99e203d2a21b8
dir: /frame.h/
typedef struct Frame Frame;
struct Frame {
	uvlong dt;
	int w, h;
	struct {
		int left, top, right, bottom;
	}crop;
	u8int *yuv[3];
	int ystride;
	int uvstride;
	u8int data[1];
};
Frame *newframe(int w, int h, u8int *yuv[3], int ystride, int vstride);