typedef struct Decoder Decoder;typedef struct Decoderops Decoderops; struct Decoder {	Stream *s;	Channel *frames;	Channel *finished;	Decoderops *ops;	double timebase;	uvlong decodetime; 	void *aux;	char info[128];}; struct Decoderops {	int (*open)(Decoder *d);	void (*close)(Decoder *d);}; Decoder *Dopen(Stream *s);void Dclose(Decoder *d);