Once the FOURCC is obtained, the appropriate CODEC procedure is determined and loaded. The following example illustrates the ioDetermineCodec routine, which determines which CODEC procedure to load. This routine first queries the hardware to determine what CODEC mode the hardware requires. Next, it queries the MMPMMMIO.INI file to determine if there is a CODEC procedure that matches the FOURCC, compression type, and capability flags received from the open routine. If no default CODEC is found, this routine queries the MMPMMMIO.INI file to find a compression type that works for this particular hardware. If there is no CODEC procedure known to the INI file that will match the FOURCC, the code searches internal CODEC tables for the necessary CODEC to load. The ULIOT sample provides an internal CODEC table located in the ULGDAT.C file (shown in the following example). This table is hard coded in the IOProc to specify what CODEC procedure to call.
LONG ioDetermineCodec ( PINSTANCE pinstance,
ULONG ulSearchFlags,
PCODECINIFILEINFO pcifi )
{
LONG rc = MMIO_SUCCESS; /* Return code of IOProcs call */
USHORT i; /* Loop index */
ULONG ulFlags;
HPS hps; /* Use to query color support */
HAB hab; /* anchor block */
HMQ hmq; /* anchor block */
if (pcifi->ulCapsFlags & CODEC_DECOMPRESS) {
/* Query the display mode */
if (ulNumColors == 0) { /* Get this info once per process */
hab = WinInitialize(0);
// hmq = WinCreateMsgQueue( hab, 0L );
hps = WinGetPS(HWND_DESKTOP);
DevQueryCaps ( GpiQueryDevice(hps),
CAPS_COLORS,
1L,
(PLONG)&ulNumColors);
WinReleasePS (hps);
// WinDestroyMsgQueue( hmq );
WinTerminate (hab);
}
/* Set the color depth for the CODEC we want */
if (ulNumColors == 16)
pcifi->ulCapsFlags |= CODEC_4_BIT_COLOR;
else if (ulNumColors > 256)
pcifi->ulCapsFlags |= CODEC_16_BIT_COLOR;
else /* 256 and anything else */
pcifi->ulCapsFlags |= CODEC_8_BIT_COLOR;
}
/********************************************************************/
/* Search for the DEFAULT CODEC of this type from the MMIO INI file */
/********************************************************************/
pcifi->ulCapsFlags |= CODEC_DEFAULT; /* Pick default */
ulFlags = ulSearchFlags |
MMIO_MATCHFOURCC |
MMIO_MATCHCOMPRESSTYPE |
MMIO_MATCHCAPSFLAGS |
MMIO_MATCHFIRST |
MMIO_FINDPROC;
if (!(rc = mmioIniFileCODEC(pcifi,ulFlags))) {
return(MMIO_SUCCESS);
}
/********************************************************************/
/* If no default, find first one and use it from the MMIO INI file */
/********************************************************************/
pcifi->ulCapsFlags &= ~CODEC_DEFAULT;
ulFlags = ulSearchFlags |
MMIO_MATCHFOURCC |
MMIO_MATCHCOMPRESSTYPE |
MMIO_MATCHCAPSFLAGS |
MMIO_MATCHFIRST |
MMIO_FINDPROC;
/* Match the fourcc, compress type, caps flags */
if (!(rc = mmioIniFileCODEC(pcifi,ulFlags))) {
return(MMIO_SUCCESS);
}
/*********************************************************************/
/* Search any internal CODEC tables for the necessary CODEC to load. */
/* Note: This is used for debugging new CODECs that have not been */
/* added to the MMPMMMIO.INI file. */
/*********************************************************************/
for (i = 0; i < NUMBER_CODEC_TABLE; i++) {
if ((acifiTable[i].ulCompressType == pcifi->ulCompressType) &&
((acifiTable[i].ulCapsFlags & pcifi->ulCapsFlags)
== pcifi->ulCapsFlags)) {
*pcifi = acifiTable[i]; /* Copy contents */
return(MMIO_SUCCESS);
}
}
return(MMIOERR_CODEC_NOT_SUPPORTED);
}
The following example illustrates how to hardcode a CODEC INI file information structure in an IOProc if the table is not represented in the MMPMMMIO.INI file.
CODECINIFILEINFO acifiTable[] = {
{
sizeof(CODECINIFILEINFO),
FOURCC_FFIO,
"ULBDC4",
/* szDCIODLLName[]-Decompression IOProc DLL name */
"CodecEntry",
/* szDCIOProcName[]-Decomp IOProc entry pt proc name */
UM_VIDEO_COMPRESSION_TYPE_BH146,
/* ulDecompressionType - ID of each decompression type */
0L,
MMIO_MEDIATYPE_DIGITALVIDEO,
CODEC_DECOMPRESS+ /* ulCapsFlags - Capabilities Flag */
CODEC_SELFHEAL+ /* ulCapsFlags - Capabilities Flag */
CODEC_ORIGIN_UPPERLEFT+ /* ulCapsFlags - Capabilities Flag */
CODEC_4_BIT_COLOR, /* ulCapsFlags - Capabilities Flag */
0,
0,
0,
0,
0,
8,
8,
0,
},
{
sizeof(CODECINIFILEINFO),
FOURCC_FFIO,
"ULBDC8",
/* szDCIODLLName[]-Decompression IOProc DLL name */
"CodecEntry",
/* szDCIOProcName[]-Decomp IOProc entry pt proc name */
UM_VIDEO_COMPRESSION_TYPE_BH146,
/* ulDecompressionType - ID of each decompression type */
0L,
MMIO_MEDIATYPE_DIGITALVIDEO,
CODEC_DECOMPRESS+ /* ulCapsFlags - Capabilities Flag */
CODEC_SELFHEAL+ /* ulCapsFlags - Capabilities Flag */
CODEC_ORIGIN_UPPERLEFT+ /* ulCapsFlags - Capabilities Flag */
CODEC_MULAPERTURE+ /* ulCapsFlags - Capabilities Flag */
CODEC_DIRECT_DISPLAY+ /* ulCapsFlags - Capabilities Flag */
CODEC_8_BIT_COLOR, /* ulCapsFlags - Capabilities Flag */
0,
0,
0,
0,
0,
8,
8,
0,
},
{
sizeof(CODECINIFILEINFO),
FOURCC_FFIO,
"ULBDC16",
/* szDCIODLLName[]-Decompression IOProc DLL name */
"CodecEntry",
/* szDCIOProcName[]-Decomp IOProc entry point proc name */
UM_VIDEO_COMPRESSION_TYPE_BH146,
/* ulDecompressionType - ID of each decompression type */
0L,
MMIO_MEDIATYPE_DIGITALVIDEO,
CODEC_DECOMPRESS+ /* ulCapsFlags - Capabilities Flag */
CODEC_SELFHEAL+ /* ulCapsFlags - Capabilities Flag */
CODEC_ORIGIN_UPPERLEFT+ /* ulCapsFlags - Capabilities Flag */
CODEC_DIRECT_DISPLAY+ /* ulCapsFlags - Capabilities Flag */
CODEC_16_BIT_COLOR, /* ulCapsFlags - Capabilities Flag */
0,
0,
0,
0,
0,
8,
8,
0,
},
};