fixed fractional_decimator_ff for N=6 interpolator, still interesting effect on the spectrum

csdr.c

@@ -1345,7 +1345,7 @@ int main(int argc, char *argv[])
 		//for(int=0;i<taps_length; i++) fprintf(stderr,"%g ",taps[i]);
 
 		fprintf(stderr,"fractional_decimator_ff: not using taps\n");
-		fractional_decimator_ff_t d = fractional_decimator_ff_init(rate, 4, NULL, 0); 
+		fractional_decimator_ff_t d = fractional_decimator_ff_init(rate, 6, NULL, 0); 
 		for(;;)
 		{
 			FEOF_CHECK;

libcsdr.c

@@ -759,7 +759,7 @@ void fractional_decimator_ff(float* input, float* output, int input_size, fracti
 		output[oi++]=acc;
 	}
 	d->input_processed = FD_INDEX_LOW + d->xifirst;
-	d->where -= d->input_processed + d->xifirst + 1;
+	d->where -= d->input_processed;
 	d->output_size = oi;
 }