midiOutCachePatches

Article
12/10/2007

The midiOutCachePatches function requests that an internal MIDI synthesizer device preload and cache a specified set of patches.

MMRESULT midiOutCachePatches(
  HMIDIOUT hmo,         
  UINT wBank,           
  WORD * lpPatchArray,  
  UINT wFlags           
);

Parameters

hmo

Handle to the opened MIDI output device. This device must be an internal MIDI synthesizer. This parameter can also be the handle of a MIDI stream, cast to HMIDIOUT.

wBank

Bank of patches that should be used. This parameter should be set to zero to cache the default patch bank.

lpPatchArray

Pointer to a PATCHARRAY array indicating the patches to be cached or uncached.

wFlags

Options for the cache operation. It can be one of the following flags.

Value	Meaning
MIDI_CACHE_ALL	Caches all of the specified patches. If they cannot all be cached, it caches none, clears the PATCHARRAY array, and returns MMSYSERR_NOMEM.
MIDI_CACHE_BESTFIT	Caches all of the specified patches. If they cannot all be cached, it caches as many patches as possible, changes the PATCHARRAY array to reflect which patches were cached, and returns MMSYSERR_NOMEM.
MIDI_CACHE_QUERY	Changes the PATCHARRAY array to indicate which patches are currently cached.
MIDI_UNCACHE	Uncaches the specified patches and clears the PATCHARRAY array.

Return Values

Returns MMSYSERR_NOERROR if successful or an error otherwise. Possible error values include the following.

Value	Description
MMSYSERR_INVALFLAG	The flag specified by wFlags is invalid.
MMSYSERR_INVALHANDLE	The specified device handle is invalid.
MMSYSERR_INVALPARAM	The array pointed to by lpPatchArray is invalid.
MMSYSERR_NOMEM	The device does not have enough memory to cache all of the requested patches.
MMSYSERR_NOTSUPPORTED	The specified device does not support patch caching.

Remarks

Some synthesizers are not capable of keeping all patches loaded simultaneously and must load data from disk when they receive MIDI program change messages. Caching patches ensures that the specified patches are immediately available.

Each element of the PATCHARRAY array represents one of the 128 patches and has bits set for each of the 16 MIDI channels that use the particular patch. The least-significant bit represents physical channel 0, and the most-significant bit represents physical channel 15 (0x0F). For example, if patch 0 is used by physical channels 0 and 8, element 0 would be set to 0x0101.

This function applies only to internal MIDI synthesizer devices. Not all internal synthesizers support patch caching. To see if a device supports patch caching, use the MIDICAPS_CACHE flag to test the dwSupport member of the MIDIOUTCAPS structure filled by the midiOutGetDevCaps function.

Requirements

**  Windows NT/2000/XP:** Included in Windows NT 3.1 and later.
**  Windows 95/98/Me:** Included in Windows 95 and later.
**  Header:** Declared in Mmsystem.h; include Windows.h.
**  Library:** Use Winmm.lib.

midiOutCachePatches

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