fir() in DSPLib using 5505 USB stick

Hii,

I am trying to replace a routine filter function with fir() in DSPLib.My doubts are as follows:

(1) Does fir() works for a sample by sample basis?

(2) I tried to work fir() for sample by sample basis. I have put 2 cases: 1 case:without any processing for audio signal

case 2: after filtering the audio signal.

I can hear the signal for case 1,but when case2,the music stops and again resumes...y is it so?

DATA r; //DATA is a dataype

NX = 1;
 NH = 51;
  for (i=0; i<NH+2; i++) db[i] = 0;      // clear delay buffer (a must)

  // compute			// fir(x, h, r, dbptr, NX, NH);
      

fir((DATA*)&mono_input,(DATA*)Hamming_Low_Pass_Filter_500Hz,r,dbptr,NX,NH);

left_output = r[0];
fir((DATA*)&mono_input,(DATA*)Hamming_High_Pass_Filter_500Hz,&r[1],dbptr,NX,NH);
right_output = r[1];

Plz reply asap.

Regards,

James