VB Forum / General / August 2004

I am trying to call the acmStreamPrepareHeader function in the msacm32.dll
library as follows:

Public Declare Auto Function acmStreamPrepareHeader Lib "msacm32.dll" (ByVal
has As IntPtr, ByRef pash As sACMSTREAMHEADER, ByVal fdwPrepare As Int32) As
Int16

mmr = acmStreamPrepareHeader(hstr, strhdr, 0)

where hstr is an IntPtr returned by a preceding acmStreamOpen call and
strhdr is defined as:

<StructLayout(LayoutKind.Sequential, CharSet:=CharSet.Auto)> Public
Structure sACMSTREAMHEADER
   Dim cbStruct As Int32
   Dim fdwStatus As Int32
   Dim dwUser As Int32
   Dim pbSrc As Int32
   Dim cbSrcLength As Int32
   Dim cbSrcLengthUsed As Int32
   Dim cbSrcUser As Int32
   Dim pbDst As Int32
   Dim cbDstLength As Int32
   Dim cbDstLengthUsed As Int32
   Dim dwDstUser As Int32
   Dim dwReservedDriver As Int32
End Structure

and initialized as follows:

    Dim strhdr As sACMSTREAMHEADER
           strhdr.cbStruct = Marshal.SizeOf(strhdr)
           strhdr.fdwStatus = 0
           strhdr.pbSrc = pSrcWaveData.ToInt32
           strhdr.cbSrcLength = SrcWaveData.Length
           strhdr.pbDst = pDstWaveData.ToInt32
           strhdr.cbDstLength = pdwOutputBytes

where pSrcWaveData is given by
            pSrcWaveData = Marshal.AllocHGlobal(SrcWaveData.Length)

and pDstWaveData is given by
           pDstWaveData = Marshal.AllocHGlobal(pdwOutputBytes)

SrcWaveData is a byte array.

The call to acmSteamPrepareHeader always return mmr=11, which is 'one or
more invalid parameters'  What am I missing?