Open wav file in nios Eclipse

HI

I made an SOPC and I can load a sound to line out in kit DE2. But I want to load a wave file to the audio codec.

I use the function :

File *fp;

fp = fopen(wav_file,"rb");

if (fp==NULL)

printf("Error: cannot open file \n");

to open wave file. Some wave files i addded to project and the path and file name i defined. But i didn't work.

What problem i have made?

:confused::(