This function can be used to set or query various extended information. It can associate a CODEC with an I/O procedure, set the current track for multiple track files, set the playing speed of a digital video, and so forth.

#define INCL_MMIOOS2
#include <os2.h>

HMMIO            hmmio;              /*  Open file handle. */
PMMEXTENDINFO    pUserExtendmminfo;  /*  Extended information. */
ULONG            ulFlags;            /*  Flags. */
ULONG            rc;                 /*  Return codes. */

rc = mmioSet(hmmio, pUserExtendmminfo, ulFlags);