If pszReturnString is NULL or usReturnLength is 0, no data will be returned.

If the return code is MCIERR_SUCCESS and the command does return data (such as status), the string parser will convert the return data to string format if appropriate. An example is status cdaudio media present would return TRUE or FALSE. If the application requests the return value to be converted to a string by the string parser, it must specify the WAIT flag. See String Commands for a description of the media control interface strings and return values.