When the client-application is ready, it sends the ICM_DECOMPRESS_BEGIN message to the driver. The client-application sets dwParam1 and dwParam2 to the BITMAPINFO data structures describing the input and output formats. If either of the formats is incorrect, your driver should return ICERR_BADFORMAT. Your driver should create any tables and allocate any memory that it needs to decompress data efficiently. When done, return ICERR_OK.