MMIO Functions - MMIO Messages

Reprint Courtesy of International Business Machines Corporation, © International Business Machines Corporation

Multimedia Programming Reference

Introduction What's New... MCI Functions High-Level Macro Service Functions Subsystem Messages Notification Messages MCI Command Messages String Commands Memory Playlist Commands Graphic Button Control Secondary Window Functions MMIO Functions MMIO Messages CODEC Messages DIVE Functions Real-Time MIDI Functions SPI Functions Data Stream State Table SMH Messages DDCMD Messages VSD Commands SHD Messages SHC Messages Data Types Types of MIDI Messages Multimedia Specification Overview Resource Interchange File Format Multimedia File Formats RIFF Compound Files and Elements - Sharing and Access Return Codes Notices Glossary

The MMIO messages are sent to an I/O procedure as a result of an MMIO function call. For example, when an application calls mmioOpen, the MMIOM_OPEN message is sent to an I/O procedure. An application can also send the MMIO messages to an I/O procedure by issuing mmioSendMessage or by directly calling the I/O procedure.

The mmioSendMessage function should be used only to pass user-defined messages, or messages not automatically generated by an MMIO function, to the I/O procedure of the user's application.

When an application issues mmioSendMessage, it passes an hmmio parameter, which MMIO converts to an MMIOINFO block before sending the parameter to the I/O procedure. When an application calls an I/O procedure directly, a pmmioinfo parameter is passed to the I/O procedure instead of an hmmio. The following is a function prototype for a direct I/O procedure call:

LONG APIENTRY MMIOPROC (PVOID pmmioinfo, USHORT usMsg, LONG lParam1, LONG lParam2);

Message	Description
MMIOM_BEGININSERT	Requests that all subsequent Writes insert data at the current seek position.
MMIOM_BEGINRECORD	Requests all subsequent Writes be considered one logical unit by an UNDO or REDO.
MMIOM_BEGINSTREAM	Sent before the first mmioRead or mmioWrite to start the stream at the optimum rate for the file.
MMIOM_CLEAR	Requests that a specified range be deleted from a file.
MMIOM_CLOSE	Requests that the file be closed.
MMIOM_COPY	Requests that a specified range be copied to the clipboard.
MMIOM_CUT	Requests that a specified range be copied to the clipboard and then deleted.
MMIOM_ENDSTREAM	Sent after the last mmioRead or mmioWrite to end the stream.
MMIOM_DELETE	Requests that information be removed from a file.
MMIOM_ENDINSERT	Requests that all subsequent Writes overwrite data at the current seek position.
MMIOM_ENDRECORD	Indicates that the logical record operation has ended and data structures should be updated, if necessary.
MMIOM_GETCF	Obtains the handle (hmmcf) of the RIFF compound file.
MMIOM_GETCFENTRY	Requests a CTOC entry for an element of a RIFF compound file.
MMIOM_GETFORMATINFO	Requests that the IOProc return an MMFORMATINFO structure.
MMIOM_GETFORMATNAME	Requests the format name for the IOProc.
MMIOM_GETHEADER	Requests that the IOProc return media-specific information.
MMIOM_IDENTIFYFILE	Attempts to determine if any IOProc can process a file.
MMIOM_MULTITRACKREAD	Requests that data be read from a movie file.
MMIOM_MULTITRACKWRITE	Requests that data be written to a movie file.
MMIOM_OPEN	Requests that a file be opened or deleted.
MMIOM_PASTE	Requests that data from the clipboard be inserted into a file.
MMIOM_QUERYHEADERLENGTH	Requests that the IOProc return the size the header.
MMIOM_QUERYIMAGE	Requests that the IOProc return the currently selected image index in the image file.
MMIOM_QUERYIMAGECOUNT	Requests that the IOProc return the number of images stored in the image file.
MMIOM_READ	Requests that bytes be read from an open file.
MMIOM_REDO	Requests that the last logical action which was undone be redone.
MMIOM_SAVE	Requests temporary changes in a file.
MMIOM_SEEK	Requests that the current file position be moved.
MMIOM_SEEKBYTIME	Requests that the file position be moved relative to some unit of time.
MMIOM_SET	Requests that extended file information be set or queried.
MMIOM_SETHEADER	Requests that the IOProc use media-specific information when writing or accepting data.
MMIOM_SETIMAGE	Selects a new image index in the image file.
MMIOM_STATUS	Used to pass appropriate MCI_STATUS requests to an IOProc.
MMIOM_TEMPCHANGE	Requests that all subsequent Writes to the media be treated as temporary changes.
MMIOM_UNDO	Requests that the last logical action, either a delete, insert, undo, or redo, be undone.
MMIOM_WINMSG	Allows an application or an MCD to pass PM messages from a window procedure to an IOProc.
MMIOM_WRITE	Requests that the bytes be written to an open file.

The MMIO messages indicate, to the I/O procedure, the type of MMIO operation to be performed. I/O procedures can be called to process files that might or might not use the RIFF format standard.

Note

The compound-file messages must not be used while creating or appending to the compound file itself.