acmStreamUnprepareHeader function (msacm.h)

The acmStreamUnprepareHeader function cleans up the preparation performed by the acmStreamPrepareHeader function for an ACM stream. This function must be called after the ACM is finished with the given buffers. An application must call this function before freeing the source and destination buffers.

Syntax

MMRESULT ACMAPI acmStreamUnprepareHeader(
  HACMSTREAM        has,
  LPACMSTREAMHEADER pash,
  DWORD             fdwUnprepare
);

Parameters

has

Handle to the conversion steam.

pash

Pointer to an ACMSTREAMHEADER structure that identifies the source and destination buffers to be unprepared.

fdwUnprepare

Reserved; must be zero.

Return value

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

Remarks

Unpreparing a stream header that has already been unprepared is an error. An application must specify the source and destination buffer lengths (cbSrcLength and cbDstLength, respectively) that were used during a call to the corresponding acmStreamPrepareHeader. Failing to reset these member values will cause acmStreamUnprepareHeader to fail with an MMSYSERR_INVALPARAM error.

The ACM can recover from some errors. The ACM will return a nonzero error, yet the stream header will be properly unprepared. To determine whether the stream header was actually unprepared, an application can examine the ACMSTREAMHEADER_STATUSF_PREPARED flag. If acmStreamUnprepareHeader returns success, the header will always be unprepared.

Requirements

See also

Audio Compression Functions

Audio Compression Manager