acmStreamSize

The acmStreamSize function returns a recommended size for a source or destination buffer on an ACM stream.

MMRESULT acmStreamSize(
  HACMSTREAM has,          
  DWORD cbInput,           
  LPDWORD pdwOutputBytes,  
  DWORD fdwSize            
);

Parameters

has

Handle to the conversion stream.

cbInput

Size, in bytes, of the source or destination buffer. The fdwSize flags specify what the input parameter defines. This parameter must be nonzero.

pdwOutputBytes

Pointer to a variable that contains the size, in bytes, of the source or destination buffer. The fdwSize flags specify what the output parameter defines. If the acmStreamSize function succeeds, this location will always be filled with a nonzero value.

fdwSize

Flags for the stream size query. The following values are defined:

Value Meaning
ACM_STREAMSIZEF_DESTINATION The cbInput parameter contains the size of the destination buffer. The pdwOutputBytes parameter will receive the recommended source buffer size, in bytes.
ACM_STREAMSIZEF_SOURCE The cbInput parameter contains the size of the source buffer. The pdwOutputBytes parameter will receive the recommended destination buffer size, in bytes.

Return Values

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

Value Description
ACMERR_NOTPOSSIBLE The requested operation cannot be performed.
MMSYSERR_INVALFLAG At least one flag is invalid.
MMSYSERR_INVALHANDLE The specified handle is invalid.
MMSYSERR_INVALPARAM At least one parameter is invalid.

Remarks

An application can use this function to determine suggested buffer sizes for either source or destination buffers. The buffer sizes returned might be only an estimation of the actual sizes required for conversion. Because actual conversion sizes cannot always be determined without performing the conversion, the sizes returned will usually be overestimated.

In the event of an error, the location pointed to by pdwOutputBytes will receive zero. This assumes that the pointer specified by pdwOutputBytes is valid.

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 Msacm.h.
  Library: Use Msacm32.lib.

See Also

Audio Compression Manager, Audio Compression Functions

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