Pointer to a header structure. This structure is
filled in by the IOProc. If the MMIO_TRANSLATEHEADER flag was set in the
ulTranslate field of MMIOINFO
on the mmioOpen, then the header
returned is one associated with the standard presentation format for that
particular media type. Each media type has a different header.
The I/O procedure is expected to transpose native header information, as
read from the file, into the standard presentation format header before
passing the data to the caller. The currently defined values for each media
type (ulMediaType) and their respective media structures are as follows:
Note: If MMIO_NOTRANSLATE was specified on the open (default case)
then the file format native header is returned.
MMIO_MEDIATYPE_IMAGE
The data represents a still
image. Images use MMIMAGEHEADER as
the media structure.
MMIO_MEDIATYPE_AUDIO
The
data represents digital audio. Digital-audio data streams use MMAUDIOHEADER
as the media structure.
MMIO_MEDIATYPE_MIDI
The data represents MIDI streams. MIDI data streams
use MMMIDIHEADER as the media
structure.
MMIO_MEDIATYPE_DIGITALVIDEO
The
data represents digital video. Digital video data streams use MMVIDEOHEADER
as the media structure.
MMIO_MEDIATYPE_MOVIE
The data represents a movie. Movie data uses MMMOVIEHEADER
as the media structure.
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