As mentioned in the README.DNGSDK.txt file in the LibRaw distribution:
In your application
* create dng_host object (or derived object, e.g. with multithreaded) entity in your program;
* pass it to LibRaw via LibRaw::set_dng_host(dng_host *) call to enable DNG SDK use on runtime
mem_image sample does not have this pieces of code, so please test with dcraw_emu -dngsdk
As mentioned in the README.DNGSDK.txt file in the LibRaw distribution:
mem_image sample does not have this pieces of code, so please test with dcraw_emu -dngsdk