typedef struct IVF IVF;typedef struct IVFrame IVFrame; struct IVF {	uvlong ns₀;	Biobuf *v;	u32int tbdenum;	u32int tbnum;	u16int w;	u16int h;	char type[6];}; struct IVFrame {	uvlong ns;	u8int *buf;	int bufsz;	int sz;}; int ivfopen(Biobuf *v, IVF *ivf);int ivfread(IVF *ivf, IVFrame *f);