acmStreamConvert
The acmStreamConvert
function requests the ACM to perform a conversion on the specified conversion
stream. A conversion may be synchronous or asynchronous, depending on how the
stream was opened.
MMRESULT acmStreamConvert(
|
HACMSTREAM
has, |
|
|
LPACMSTREAMHEADER pash, |
|
|
DWORD fdwConvert |
|
|
); |
|
Parameters
has
Handle of the
open conversion stream.
pash
Address of a
stream header that describes source and destination buffers for a conversion.
This header must have been prepared previously by using the acmStreamPrepareHeader function.
fdwConvert
Flags for
doing the conversion. The following values are defined:
ACM_STREAMCONVERTF_BLOCKALIGN
Only integral
numbers of blocks will be converted. Converted data will end on block-aligned
boundaries. An application should use this flag for all conversions on a stream
until there is not enough source data to convert to a block-aligned
destination. In this case, the last conversion should be specified without this
flag.
ACM_STREAMCONVERTF_END
ACM
conversion stream should begin returning pending instance data. For example, if
a conversion stream holds instance data, such as the end of an echo filter
operation, this flag will cause the stream to start returning this remaining
data with optional source data. This flag can be specified with the
ACM_STREAMCONVERTF_START flag.
ACM_STREAMCONVERTF_START
ACM
conversion stream should reinitialize its instance data. For example, if a
conversion stream holds instance data, such as delta or predictor information,
this flag will restore the stream to starting defaults. This flag can be
specified with the ACM_STREAMCONVERTF_END flag.
Return Values
Returns zero
if successful or an error otherwise. Possible error values include the
following:
|
ACMERR_BUSY |
The stream
header specified in pash is currently in use and cannot be reused. |
|
ACMERR_UNPREPARED |
The stream
header specified in pash is currently not prepared by the acmStreamPrepareHeader function. |
|
MMSYSERR_INVALFLAG |
At least
one flag is invalid. |
|
MMSYSERR_INVALHANDLE |
The
specified handle is invalid. |
|
MMSYSERR_INVALPARAM |
At least
one parameter is invalid. |
Remarks
You must use
the acmStreamPrepareHeader function to prepare the source and
destination buffers before they are passed to acmStreamConvert.
If an
asynchronous conversion request is successfully queued by the ACM or driver and
the conversion is later determined to be impossible, the ACMSTREAMHEADER
structure is posted back to the application s callback function with the cbDstLengthUsed
member set to zero.
See Also