Sample Code
Windows Driver Samples/ Msfilter Sample Codec/ C++/ msfilter.c/
//==========================================================================;
//
// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY
// KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR
// PURPOSE.
//
// Copyright (c) 1992-1994 Microsoft Corporation
//
//--------------------------------------------------------------------------;
//
// msfilter.c
//
// Description:
// This file contains filter routines for doing simple
// volume and echo.
//
//
//
//==========================================================================;
#include <windows.h>
#include <windowsx.h>
#include <mmsystem.h>
#include <mmreg.h>
#include <msacm.h>
#include <msacmdrv.h>
#include "codec.h"
#include "msfilter.h"
//--------------------------------------------------------------------------;
//
// LRESULT msfilterVolume
//
// Description:
// This function handles the ACMDM_STREAM_CONVERT message. This is the
// whole purpose of writing an ACM driver--to convert data. This message
// is sent after a stream has been opened (the driver receives and
// succeeds the ACMDM_STREAM_OPEN message).
//
// Arguments:
// LPACMDRVSTREAMINSTANCE padsi: Pointer to instance data for the
// conversion stream. This structure was allocated by the ACM and
// filled with the most common instance data needed for conversions.
// The information in this structure is exactly the same as it was
// during the ACMDM_STREAM_OPEN message--so it is not necessary
// to re-verify the information referenced by this structure.
//
// LPACMDRVSTREAMHEADER padsh: Pointer to stream header structure
// that defines the source data and destination buffer to convert.
//
// Return (LRESULT):
// The return value is zero (MMSYSERR_NOERROR) if this function
// succeeds with no errors. The return value is a non-zero error code
// if the function fails.
//
//--------------------------------------------------------------------------;
LRESULT FNGLOBAL msfilterVolume
(
LPACMDRVSTREAMINSTANCE padsi,
LPACMDRVSTREAMHEADER padsh
)
{
LPVOLUMEWAVEFILTER pwfVol;
HPSHORT hpiSrc;
HPSHORT hpiDst;
HPBYTE hpbSrc;
HPBYTE hpbDst;
LONG lSrc, lDst;
LONG lAmp;
LONG lDone, lSize;
DWORD dw;
pwfVol = (LPVOLUMEWAVEFILTER)padsi->pwfltr;
//
// Source and dest sizes are the same for volume.
// block align source
//
dw = PCM_BYTESTOSAMPLES(padsi->pwfxSrc, padsh->cbSrcLength);
dw = PCM_SAMPLESTOBYTES(padsi->pwfxSrc, dw);
padsh->cbSrcLengthUsed = dw;
lSize = (LONG)dw;
lAmp = pwfVol->dwVolume;
if( padsi->pwfxSrc->wBitsPerSample == 8 ) {
hpbSrc = (HPBYTE)padsh->pbSrc;
hpbDst = (HPBYTE)padsh->pbDst;
for( lDone = 0; lDone < lSize; lDone++ ) {
lSrc = ((short)(WORD)(*hpbSrc)) - 128;
lDst = ((lSrc * lAmp) / 65536L) + 128;
if( lDst < 0 ) {
lDst = 0;
} else if( lDst > 255 ) {
lDst = 255;
}
*hpbDst = (BYTE)lDst;
if( lDone < (lSize - 1) ) {
// Will advance to invalid ptr on last sample
// So do not advance on last sample.
hpbSrc++;
hpbDst++;
}
}
} else {
hpiSrc = (HPSHORT)(padsh->pbSrc);
hpiDst = (HPSHORT)(padsh->pbDst);
for( lDone = 0; lDone < lSize; lDone += sizeof(short) ) {
lDst = ((((LONG)(int)(*hpiSrc)) * (lAmp/2)) / 32768L);
if( lDst < -32768 ) {
lDst = -32768;
} else if( lDst > 32767 ) {
lDst = 32767;
}
*hpiDst = (short)lDst;
if( lDone < (lSize - 1) ) {
// Will advance to invalid ptr on last sample
// So do not advance on last sample.
hpiSrc++;
hpiDst++;
}
}
}
padsh->cbDstLengthUsed = lDone;
return (MMSYSERR_NOERROR);
}
//--------------------------------------------------------------------------;
//
// LRESULT msfilterEcho
//
// Description:
// This function handles the ACMDM_STREAM_CONVERT message. This is the
// whole purpose of writing an ACM driver--to convert data. This message
// is sent after a stream has been opened (the driver receives and
// succeeds the ACMDM_STREAM_OPEN message).
//
// Arguments:
// LPACMDRVSTREAMINSTANCE padsi: Pointer to instance data for the
// conversion stream. This structure was allocated by the ACM and
// filled with the most common instance data needed for conversions.
// The information in this structure is exactly the same as it was
// during the ACMDM_STREAM_OPEN message--so it is not necessary
// to re-verify the information referenced by this structure.
//
// LPACMDRVSTREAMHEADER padsh: Pointer to stream header structure
// that defines the source data and destination buffer to convert.
//
// Return (LRESULT):
// The return value is zero (MMSYSERR_NOERROR) if this function
// succeeds with no errors. The return value is a non-zero error code
// if the function fails.
//
//--------------------------------------------------------------------------;
LRESULT FNGLOBAL msfilterEcho
(
LPACMDRVSTREAMINSTANCE padsi,
LPACMDRVSTREAMHEADER padsh
)
{
PSTREAMINSTANCE psi;
LPECHOWAVEFILTER pwfEcho;
DWORD dw;
HPSHORT hpiHistory;
HPSHORT hpiSrc;
HPSHORT hpiDst;
HPBYTE hpbHistory;
HPBYTE hpbSrc;
HPBYTE hpbDst;
LONG lSrc, lHist, lDst;
LONG lAmp, lDelay;
LONG lDone1, lDone2, lSize, lDelaySize;
BOOL fStart;
BOOL fEnd;
DWORD cbDstLength;
fStart = (0 != (ACM_STREAMCONVERTF_START & padsh->fdwConvert));
fEnd = (0 != (ACM_STREAMCONVERTF_END & padsh->fdwConvert));
pwfEcho = (LPECHOWAVEFILTER)padsi->pwfltr;
lAmp = pwfEcho->dwVolume;
psi = (PSTREAMINSTANCE)padsi->dwDriver;
lDone1 = 0;
lDone2 = 0;
lDelay = psi->dwPlace;
lDelaySize = padsi->pwfxSrc->nBlockAlign
* (padsi->pwfxSrc->nSamplesPerSec
* pwfEcho->dwDelay
/ 1000);
// If this is a start buffer, then zero out the history
if(fStart) {
hpbHistory = psi->hpbHistory;
for( lDone1 = 0; lDone1 < lDelaySize; lDone1++ ) {
hpbHistory[lDone1] = 0;
}
psi->dwPlace = 0L;
psi->dwHistoryDone = 0L;
}
//
// Source and dest sizes are the same for volume.
// block align source
//
dw = PCM_BYTESTOSAMPLES(padsi->pwfxSrc, padsh->cbSrcLength);
dw = PCM_SAMPLESTOBYTES(padsi->pwfxSrc, dw);
padsh->cbSrcLengthUsed = dw;
lSize = (LONG)dw;
cbDstLength = PCM_BYTESTOSAMPLES(padsi->pwfxDst, padsh->cbDstLength);
cbDstLength = PCM_SAMPLESTOBYTES(padsi->pwfxDst, cbDstLength);
if( padsi->pwfxSrc->wBitsPerSample == 8 ) {
hpbHistory = psi->hpbHistory;
hpbSrc = (HPBYTE)padsh->pbSrc;
hpbDst = (HPBYTE)padsh->pbDst;
for( lDone1 = 0; lDone1 < lSize; lDone1++ ) {
lSrc = ((short)(WORD)(*hpbSrc)) - 128;
lHist = ((short)(char)(hpbHistory[lDelay]));
lDst = lSrc + lHist + 128;
if( lDst < 0 ) {
lDst = 0;
} else if( lDst > 255 ) {
lDst = 255;
}
*hpbDst = (BYTE)lDst;
lHist = (((lDst-128) * lAmp) / 65536L);
if( lHist < -128 ) {
lHist = -128;
} else if( lHist > 127 ) {
lHist = 127;
}
hpbHistory[lDelay] = (BYTE)lHist;
lDelay++;
if( lDelay >= lDelaySize ) {
lDelay = 0;
}
if( lDone1 < (lSize - 1) ) {
// Will advance to invalid ptr on last sample
// So do not advance on last sample.
hpbSrc++;
hpbDst++;
}
}
// If this is the end block and there is room,
// then output the last echo
if(fEnd && ((DWORD)lDone1 < cbDstLength) ) {
lSize = cbDstLength - lDone1;
if( lSize > (lDelaySize - (LONG)(psi->dwHistoryDone)) ) {
lSize = lDelaySize - psi->dwHistoryDone;
}
if( lSize < 0 ) {
/* ERROR */
lSize = 0;
}
for( lDone2 = 0; lDone2 < lSize; lDone2++ ) {
*hpbDst = (BYTE)((short)(char)(hpbHistory[lDelay]) + 128);
lDelay++;
if( lDelay >= lDelaySize ) {
lDelay = 0;
}
if( lDone2 < (lSize - 1) ) {
// Will advance to invalid ptr on last sample
// So do not advance on last sample.
hpbSrc++;
hpbDst++;
}
(psi->dwHistoryDone)++;
}
}
} else {
hpiHistory = (HPSHORT)(psi->hpbHistory);
hpiSrc = (HPSHORT)(padsh->pbSrc);
hpiDst = (HPSHORT)(padsh->pbDst);
for( lDone1 = 0; lDone1 < lSize; lDone1 += sizeof(short) ) {
lDst = (LONG)(*hpiSrc) + (LONG)(hpiHistory[lDelay]);
if( lDst < -32768 ) {
lDst = -32768;
} else if( lDst > 32767 ) {
lDst = 32767;
}
*hpiDst = (short)lDst;
lHist = ( ( lDst * (lAmp/2)) / 32768L);
if( lHist < -32768 ) {
lHist = -32768;
} else if( lHist > 32767 ) {
lHist = 32767;
}
hpiHistory[lDelay] = (short)lHist;
lDelay++;
if( (LONG)(lDelay * sizeof(short)) >= lDelaySize ) {
lDelay = 0;
}
if( lDone1 < (lSize - 1) ) {
// Will advance to invalid ptr on last sample
// So do not advance on last sample.
hpiSrc++;
hpiDst++;
}
}
// If this is the end block and there is room,
// then output the last echo
if(fEnd && ((DWORD)lDone1 < cbDstLength) ) {
lSize = cbDstLength - lDone1;
if( lSize > (lDelaySize - (LONG)(psi->dwHistoryDone)) ) {
lSize = lDelaySize - psi->dwHistoryDone;
}
if( lSize < 0 ) {
/* ERROR */
lSize = 0;
}
for( lDone2 = 0; lDone2 < lSize; lDone2 += sizeof(short) ) {
*hpiDst = hpiHistory[lDelay];
lDelay++;
if( (LONG)(lDelay * sizeof(short)) >= lDelaySize ) {
lDelay = 0;
}
if( lDone2 < (lSize - 1) ) {
// Will advance to invalid ptr on last sample
// So do not advance on last sample.
hpiSrc++;
hpiDst++;
}
psi->dwHistoryDone += sizeof(short);
}
}
}
// Reset the new point/place in the history
psi->dwPlace = lDelay;
padsh->cbDstLengthUsed = lDone1 + lDone2;
return (MMSYSERR_NOERROR);
}
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