wParam = (DWORD) (LPVOID) lpbiInput;
lParam = (DWORD) (LPVOID) lpbiOutput;
Notifies a video decompression driver to prepare to decompress data.
When the driver receives this message, it should allocate buffers and do any time-consuming operations so that it can process ICM_DECOMPRESS messages efficiently.
If you want the driver to decompress data directly to the screen, send the ICM_DRAW_BEGIN message.
ICM_DECOMPRESS_BEGIN and ICM_DECOMPRESS_END do not nest. If your driver receives an ICM_DECOMPRESS_BEGIN message before decompression is stopped with ICM_DECOMPRESS_END, it should restart decompression with new parameters.
ICM_COMPRESS_BEGIN, ICM_DECOMPRESS, ICM_DECOMPRESS_END, ICM_DRAW_BEGIN